Tutorial By general course organic chemistry compiled on the basis of many years of experience in a student workshop in organic chemistry at the Faculty of Chemistry of Moscow State University. M. V. Lomonosov. Contains methods for the synthesis of organic compounds of various classes. The general rules and methods of work in an organic workshop are outlined, general instructions on the interpretation of 1 H and 13 C NMR spectra of synthesized compounds. For students, graduate students and teachers of chemical universities, as well as researchers.
First aid for burns, poisoning and other accidents.
For mild thermal burns, wash the affected area with a stream of cold water, rinse with alcohol, and then lubricate with glycerin or boric petroleum jelly. For severe burns, wash the affected area with a stream of cold water and call a doctor.
In case of bromine burns, wash the affected area thoroughly with a stream of cold water and then with a 10% solution of sodium thiosulfate. After inhaling bromine vapor, you should sniff a dilute ammonia solution and go to the Fresh air. In case of any damage to the eyes or respiratory tract by bromine, the teacher should be immediately notified and the victim should be sent to a medical facility to provide qualified assistance.
In case of burns with phenol or its solution, wipe the whitened area of skin with alcohol until then. until normal skin color is restored, then rinse the affected area with water and apply a compress of cotton wool or gauze soaked in glycerin.
In case of burns with concentrated acid solutions, wash the burned area with a stream of cold water and then with a 3% soda solution. If acid gets into your eyes, rinse under running cold water for 5 minutes and consult a doctor.
For burns with concentrated alkali solutions, wash the skin with a stream of cold water and then with a 1% solution of boric acid. Ammonia and amines have almost no effect on the skin, but if they get into the eyes they can cause severe damage. If alkalis or other bases get into your eyes, rinse them immediately with a stream of water and notify your teacher at the same time. Continue rinsing for several minutes, slightly lifting the eyelid. If alkali or bases come into contact with your eyes, you should always consult a doctor - even if you do not discomfort!
If reagents accidentally enter the body, immediately drink at least a glass of water and notify the teacher.
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Preface
PART I WORKING METHODS WHEN CARRYING OUT ORGANIC SYNTHESIS
Chapter I. Work organization and safety precautions
1. General rules work in the laboratory of organic synthesis
2. Precautionary measures and first aid in case of accidents
Working with toxic and caustic substances
Working with flammable and explosive substances
Rules for handling glass
First aid for burns, poisoning and other accidents
Extinguishing local fires and burning clothing
3. Basic laboratory chemical glassware
4. Assembly of devices
5. Washing and drying chemical glassware
6. Use of literature and rules for writing a report
Chapter II. Basic operations when working in a chemical laboratory
1. Heating
2. Cooling
3. Temperature measurement and control
4. Grinding and mixing
5. Dissolution and properties of some organic solutions and gels
Ethanol
Methyl alcohol
Diathyl ether
Petroleum ether
Acetone
6. Drying and basic dryers
Gas drying
Drying organic liquids
Drying solids
Basic dehumidifiers
7. Filtration
Filtration at normal pressure
Vacuum filtration
Chapter III. Methods for purifying organic substances
1. Crystallization
Solvent selection
Carrying out recrystallization
Crystal separation
2. Sublimation (sublimation)
3. Extraction
4. Distillation
Simple distillation at atmospheric pressure
Steam distillation
Distillation under reduced pressure
Fractional distillation
Rectification
5. Chromatography
Adsorption chromatography
Partition chromatography
Paper chromatography
Ion exchange chromatography
Chapter IV. Determination of the most important constants of organic compounds
1. Melting point
2. Boiling point
3. Relative density
4. Refractive index
5. Molecular weight
Chapter V. Working with compressed and liquefied gases
1. Gas cylinders and their handling
2. Gas dosing
3. Purification and introduction of gases into the device
4. Safety rules when working with gas cylinders
Chapter VI. Quantitative elemental analysis of organic substances
1. Determination of carbon and hydrogen by semi-micro method
Installation assembly
Performing an Analysis
2. Determination of nitrogen by semi-micromethod (according to Dumas)
Installation assembly
Performing an Analysis
3. Determination of carbon and hydrogen by micromethod
Installation assembly
Performing an Analysis
PART II SYNTHESIS OF ORGANIC SUBSTANCES
Chapter VII. Halogenation reactions
1. Substitution hydroxyl group halogen fuel
2. Replacement of the hydroxyl group of acids with halogen
3. Addition of a halogen through a multiple bond
4. Direct replacement of hydrogen with halogen
5. Examples of syntheses
Ethyl bromide
(?)-Bromonaphthalene and ethyl bromide
Ethyl iodide
Butyl bromide
Acetyl chloride
Benzoyl chloride
1,2-Dibromoethane
Bromobenzene
(?)-Bromonaphthalene
(?)-Bromanisole
Chapter VIII. Alkylation reactions
1. Alkylation of aromatic hydrocarbons with alcohols in the presence of sulfuric acid
2. Preparation of ethers
3. Examples of syntheses
sec-Butylbenzene
Dibutyl ether
Isoamyl ester
Diphenyl ether
Phenetol
Ethyl ester (?)-naphthol (nerolin new, bromeliad)
Anisole
Chapter IX. Acylation reactions
1. Acylation of alcohols and amines with carboxylic acids
2. Acylation of alcohols, phenols and amines with acid chlorides
3. Acylation of alcohols, phenols and amines with acid anhydrides
4. Examples of syntheses
Ethyl acetate ether
Acetic isoamyl ester
Ethyl chloroacetic acid
Oxalic acid diethyl ester
Benzoic acid ethyl ester
Benzanilide
Aspirin (acetylsalicylic acid)
(?)-Naphthyl acetate
Acetanilide
Chapter X. Friedel-Crafts reactions
1. Alkylation of aromatic compounds
2. Acylation of aromatic compounds
3. Examples of syntheses
Isopropylbenzene
Diphenylmethane
Acetophenone
Benzophenone
Chapter XI. Oxidation reactions
1. Oxidation at a double bond
2. Oxidation of primary and secondary alcohols to aldehydes or ketones
3. Oxidation of aldehydes and ketones to acids
4. Oxidation of methyl and methylene groups
5. Preparation of quinones by oxidation
6. Examples of syntheses
Acetaldehyde
Propionic aldehyde
Isovaleric aldehyde
Benzophenone
Isobutyric acid
Valeric acid
Benzoic acid
Benzoquinone
Anthraquinone
Chapter XII. Nitration reactions
1. Nitration of fatty hydrocarbons
2. Nitration of aromatic hydrocarbons
3. Examples of syntheses
Nitromethane
Nitrobenzene
(?)- and (?)-Nitrotoluene
(?)- and (?)-Nitrophenol
(?)-Nitronaphthalene
Chapter XIII. Amination reactions
1. Preparation of fatty amines
2. Preparation of aromatic amines
3. Examples of syntheses
Methylamine
Aniline
(?)- and (?)-Toluidine
(?)-Naphthylamine
Chapter XIV. Sulfonation reactions
1. Sulfonation of aromatic compounds
2. Examples of syntheses
(?)-Naphthalene sulfonic acid (sodium salt)
Benzenesulfonic acid (sodium salt)
(?)-Toluenesulfonic acid
Sulfanilic acid
Chapter XV. Diazotization and azo coupling reactions
1. Reactions of diazonium salts accompanied by the release of nitrogen
2. Reactions of diazonium salts that occur without the release of nitrogen
3. Examples of syntheses
Phenol
Iodobenzene
heliantine
(?)-Naphthalorange
Chapter XVI. Grignard reactions
1. Production of hydrocarbons
Quantitative determination of active hydrogen according to Chugaev-Tserevitinov
2. Preparation of carboxylic acids
3. Preparation of alcohols
4. Examples of syntheses
Phenylacetic acid
Triphenylcarbinol
Diphenylcarbinol (benzhydrol)
Chapter XVII. Cannnzzaro's reaction
Synthesis of benzoic acid and benzyl alcohol
Chapter XVIII. Claisen reaction
Examples of syntheses
Acetoacetic ester
benzoidacetor
Chapter XIX. Polymerization and polycondensation reactions
1. Polymerization
2. Polycondensation
3. Examples of syntheses
Paraldehyde
Polystyrene
Polymethyl methacrylate
Copolymer of styrene with methyl methacrylate
Methyl methacrylate (from polymethyl methacrylate)
Glyphthalic resin
Phenol-formaldehyde resin
Chapter XX. Identification
1. Preliminary tests
2. Qualitative reactions
3. Derivation
Recommended reading
Applications
1. Drying agents for organic compounds
2. Water vapor pressure at different temperatures
3. Pressure of liquefied gases in cylinders
4. Color of compressed gas cylinders
5. Density of sulfuric acid solutions (20°C)
6. Density of hydrochloric acid solutions (20°C)
7. Density of solutions nitric acid(20°C)
8. Density of caustic soda solutions (20°C)
9. Density of caustic potash solutions (20°C)
10. Physical properties of alcohols and their derivatives
11. Physical properties of phenols and their derivatives
12. Physical properties of aldehydes and their derivatives
13. Physical properties of ketones and their derivatives
14. Physical properties of carboxylic acids and their derivatives
15. Physical properties of primary and secondary amines and their derivatives
16. Physical properties of alkyl halides and their derivatives
MINISTRY OF HIGHER AND SECONDARY SPECIAL EDUCATION OF THE REPUBLIC OF UZBEKISTAN
A. KARIMOV, N. CHINIBEKOVA
PRACTICUM
IN ORGANIC CHEMISTRY
Textbook for students of pharmaceutical institutes
Tashkent -2009
Reviewers:
Akhmedov K. - Doctor of Chemical Sciences, Professor of the Department
organic chemistry of the Uzbek National
university
Kurbonova M. - Candidate of Pharmaceutical Sciences, Associate Professor of the Department
inorganic, analytical and physical colloidal chemistry
Tashkent Pharmaceutical Institute
Introduction
I. LABORATORY TECHNIQUES
I.1 Laboratory safety and first aid measures
I.2 Chemical glassware and accessories
I.3 Basic operations when working in an organic chemistry laboratory
I.3.1 Heating
I.3.2 Cooling
I.3.3 Grinding
I.3.4 Stirring
I.3.5 Drying
I.4.Methods of isolation and purification of substances
I.4.1 Filtering
I.4.2 Crystallization
I.4.3 Sublimation
I.4.4 Distillation
I.5 The most important physical constants
I.5.1 Melting point
I.5.2 Boiling point
II. methods for determining the structure of organic compounds
II.1 Qualitative elemental analysis of organic compounds
III basics of structure, properties and identification of organic compounds
III.1 Classification, nomenclature, spatial structure and isomerism of organic compounds
III.2 Chemical bonding and mutual influence of atoms in organic compounds
III.3 Alkanes. Cycloalkanes
III.4 Alkenes, alkadienes, alkynes
III.5 Arenas
III.6 Halogenated hydrocarbons
III.7 Alcohols
III.8 Phenols
III.9 Ethers
III.10 Aldehydes. Ketones
III.11 Amines
III.12 Diazo-, azo-compounds
III.13 Mono- and dibasic carboxylic acids
III.14 Heterofunctional carboxylic acids
III.14.1 Hydroxy-, phenolic acids
III.14.2 Oxoacids
III.14.3 Amino acids. Amides. Ureide acids
III.15 Five-membered heterocyclic compounds
III.15.1 Five-membered heterocyclic compounds with one heteroatom
III.15.2 Five-membered heterocyclic compounds with two heteroatoms
III.16 Six-membered heterocyclic compounds
III.16.1 Six-membered heterocyclic compounds with one heteroatom
III.16.2 Six-membered heterocyclic compounds with two heteroatoms
III.17 Fused heterocyclic compounds
III.18 Carbohydrates
Ш.18.1 Monosaccharides
Sh.18.2 Polysaccharides
III.19 Saponifiable and unsaponifiable lipids
IV syntheses of organic compounds
IV.1 Halogenation
IV.1.1 1-Bromobutane
IV.1.2 Bromoethane
IV.1.3 Bromobenzene
IV.2 Sulfonation
IV.2.1 p-Toluenesulfonic acid
IV.2.2 p-Toluenesulfonic acid sodium
IV.2.3 Sulfanilic acid
IV.3 Acylation
IV.3.1 Ethyl acetate
IV.3.2 Acetylsalicylic acid
IV.3.3 Acetanilide
IV.4 Preparation of glycosides
IV.4.1 N-glycoside of white streptocide
V. Literature
INTRODUCTION
Organic chemistry occupies an important place in the system of higher pharmaceutical education, being one of the fundamental sciences that forms the scientific, theoretical and experimental basis both for the acquisition of specialized knowledge in pharmaceutical chemistry, pharmacognosy, pharmacology, toxicological chemistry, and for the professional activities of a pharmacist. The use of this knowledge when performing qualitative reactions on functional groups, obtaining individual representatives of various classes of organic compounds, and conducting characteristic reactions with them contributes to a deeper assimilation of theoretical material.
Today, the development of organic chemistry is accompanied by the emergence of a huge number of new substances: in the general list of medicines, over 90% are organic substances. This, in turn, predetermines the need to understand and improve experimental techniques and research methods. In this regard, the training of pharmaceutical specialists who need knowledge of organic chemistry requires not only theoretical training, but also versatile practical skills and abilities in conducting chemical experiments.
Workshop on Organic Chemistry" is a logical continuation of the lecture course on this subject and represents a single educational and methodological complex that promotes creative approach to study the discipline, conduct practical classes taking into account modern methods training (interactive, innovative). This manual allows you to become familiar with some of the methods for obtaining individual representatives of the classes of organic chemistry in the laboratory in the presence of small quantities of starting substances, reagents and relatively simple equipment.
Included in almost every topic, the workshop is aimed at enabling the student to experimentally see the manifestation of the most important chemical properties characteristic of functional groups that determine the reactivity of a compound. Indeed, in professional activities, sometimes, with the help of seemingly simple chemical tests, the authenticity of a medicinal substance will be determined, the question of the presence or absence of a particular component in a mixture will be resolved, etc. It is important to understand what chemical processes cause the appearance of the external effect (the appearance of color, odor, etc.).
This manual embodies the experience of many years of work of the team of the Department of Organic Chemistry of the Tashkent Pharmaceutical Institute, on the basis of which the structure of the workshop for students of the pharmaceutical specialty was determined.
The workshop includes four sections and a list of recommended literature.
In the first section on technology laboratory work, information about chemical glassware and auxiliary devices is presented, the main operations of practical work, methods for isolating and purifying substances, and determining the most important physical constants are considered.
The second section discusses methods for establishing the structure of organic compounds and provides a qualitative elemental analysis of the study of the structure of organic substances.
The third section includes information on the structure, properties and identification of organic compounds. For each topic, general theoretical questions and answers to them are given, Control questions and exercises and practical experiments with a detailed description of the ongoing chemical processes.
The fourth section presents syntheses of some organic compounds that can be performed in the laboratory.
I. LABORATORY TECHNIQUES
I.1 LABORATORY SAFETY AND FIRST AID MEASURES
GENERAL SAFETY RULES FOR WORK IN CHEMICAL LABORATORIES
When working in an organic chemistry laboratory, a student must clearly understand the specifics of organic compounds, their toxicity, and flammability, which requires especially careful handling of them and compliance with certain rules.
1.In the laboratory, the student works in a robe that fastens in the front (the robe can be easily removed in case of fire). At the workplace, in addition to a stand with test tubes and reagents, there is only a work diary and a soft napkin. 2.Before starting work, you need to carefully study its description and know the properties of the resulting substances. .When performing work, you must be careful and careful. Inattention and ignorance of the properties of the substances with which the student will work can lead to an accident. .When heating chemicals in a test tube, it is necessary to secure it in an inclined position so that its opening is directed in the direction opposite to itself and not towards the comrades working nearby. Heat the test tube gradually, moving the burner flame across the test tube from top to bottom. .When working with a gas outlet tube, the heating of the test tube can be stopped only by first removing the end of the tube from the receiver with the liquid. If the heat source is removed prematurely, liquid from the receiver may be sucked into the reaction tube, causing it to burst and splashing the reaction mixture on your face and hands. .No substances may be tasted in the laboratory. .When determining the smell, vapor from a test tube or bottle is directed towards you with a movement of the hand. .All experiments with substances with a strong irritating odor should be carried out only under traction. .Sodium metal is cut with a sharp, dry knife on filter paper. The trimmings and leftovers are immediately removed into special bottles filled with dry kerosene or petroleum jelly. The reaction with sodium metal should be carried out in a completely dry container. 10.Combustible and flammable liquids (ether, benzene, alcohol) are poured away from fire, test tubes and flasks with them are heated in a water or sand bath. 11.When a liquid in a vessel ignites, it is necessary, first of all, to extinguish the heat source, and then cover the flame with a napkin or cup. If a burning liquid is spilled on a table or floor, extinguish it only with sand or cover it with a thick piece of cloth. It is not recommended to use water for extinguishing, since organic substances, as a rule, do not mix with water and spread with it, spreading the flame. .When clothing catches fire, you must immediately cover the person who is burning with a blanket or thick outer clothing. .When diluting sulfuric acid with water, the sulfuric acid should be added in a thin stream to the water (and not vice versa) while continuously stirring the solution. .It is forbidden to take alkali metals (potassium, sodium, their hydroxides) with bare hands, as well as suck acids, alkalis and solvents into your mouth. .Bottles with shared reagents should always be on shared shelves. .Remains of flammable liquids, acids, and alkalis should be poured not into the sink, but into special bottles. .After finishing the work and handing it over to the workshop teacher, the student must tidy up his workplace, check whether electrical appliances, water, and gas are turned off. FIRST AID Each first aid laboratory should have a first aid kit with absorbent cotton wool, sterile swabs and bandages, adhesive plaster, 3-5% alcohol solution of iodine, 1% acetic acid solution, 1-3% bicarbonate of soda solution, 2% boric acid solution, glycerin , Vaseline, burn ointment, ethyl alcohol, ammonia. Burns from fire or hot objects are quickly treated with burn ointment, then cotton wool with this ointment is applied and loosely bandaged. Manganese potassium and alcohol are also used to pre-treat the burned area. In case of severe burns, the victim is sent to an outpatient clinic. In case of chemical burns (skin contact with acid, alkali or bromine), the area affected by the acid is washed large quantity m of water, then a 3% solution of bicarbonate of soda, lubricate with ointment for burns or Vaseline and bandage. The area of skin on which the alkali has come into contact is immediately washed with plenty of water, then with a 1% solution of acetic acid, lubricated with burn ointment or Vaseline and bandaged. If bromine gets on your skin, immediately wash it with benzene, gasoline or a saturated hyposulfite solution. If acid gets into the eye, it is immediately washed with plenty of water, then with a diluted soda solution, again with water, and the victim is immediately sent to an outpatient clinic. If alkali gets into the eye, it is immediately washed with a large amount of water, then with a diluted solution of boric acid, and the victim is immediately sent to an outpatient clinic. Fabric of clothing that has been exposed to acid or alkali is washed with plenty of water, then treated with a 3% solution of bicarbonate of soda (in case of acid) or 1% solution of acetic acid (if alkali is exposed). Hand cuts from glass are washed with a strong stream of water, the fragments are removed from the wound, filled with an alcohol solution of iodine and bandaged. I.2 CHEMICAL COOKWARE AND ACCESSORIES Basic laboratory chemical glassware includes flasks, beakers, test tubes, cups, funnels, refrigerators, reflux condensers and other vessels various designs. Chemical glassware is made from various brands of glass; it is resistant to various temperatures, most chemical reagents, transparent, and easy to clean. Depending on the purpose, flasks are made of different volumes and shapes (Fig. 1.1). Rice. 1.1. Flasks: a) round-bottomed, b) flat-bottomed, c) round-bottomed with two and three necks at an angle, d) conical (Erlenmeyer flask, e) Kjeldahl flask, f) pear-shaped, g) pointed-bottomed, h) round-bottomed for distillation (Wurtz flask) , i) sharp-bottomed for distillation (Claisen flask), j) Favorsky flask, k) flask with a tube (Bunsen flask). organic chemistry synthesis compound Round bottom flasks are designed for high temperature operation, atmospheric distillation and vacuum operation. The use of round-bottomed flasks with two or more necks allows several operations to be performed simultaneously during the synthesis process: use a stirrer, refrigerator, thermometer, dropping funnel, etc. Flat-bottomed flasks are only suitable for use at atmospheric pressure and for storing liquid substances. Conical flat-bottomed flasks are widely used for crystallization because their shape provides minimal surface area for evaporation. Thick-walled conical flasks with a tube (Bunsen flasks) are used for filtration under vacuum up to 1.33 kPa (10 mmHg) as filtrate receivers. The glasses (Fig. 1.2, a) are intended for filtering, evaporation (at a temperature of no more than 1000C), preparing solutions in the laboratory, as well as for carrying out certain syntheses, in which dense precipitates are formed that are difficult to remove from the flasks. Glasses are not used when working with low-boiling and flammable solvents. Rice. 1.2. Chemical glassware: a) glass, Fig. 1.3. Porcelain cup b) bottle Bulks (Fig. 1.2, b) are used for weighing and storing volatile, hygroscopic and easily oxidized substances in air. Cups (Fig. 1.3) are used for evaporation, crystallization, sublimation, drying, grinding and other operations. Test tubes (Fig. 1.4) are produced in various capacities and are used to analyze small quantities of test substances. Test tubes with a cone joint and an outlet tube are used for filtering small volumes of liquids under vacuum. To measure the volume of liquid, measuring vessels are used: measuring cups, cylinders, volumetric flasks, pipettes, burettes (Fig. 1.5). Rice. 1.4. Test tubes: a) cylindrical with Fig. 1.5. Volumetric glassware: 1) beaker, unfolded edge, b) cylindrical 2) cylinder, 3) volumetric flask, without bend, c) pointed-bottomed (centrifuge - 4) graduated pipettes, d) with interchangeable cones - 5) Mohr pipette, 6) pipette with thin sections, e) with a cone joint and with a piston, 7) burette with an outlet tube For rough measuring of liquids, beakers are used - conical glasses expanding upward with marked divisions and graduated cylinders. To measure large fixed volumes of liquids, volumetric flasks are used; their capacity ranges from 10 ml to 2 liters, and for accurate measuring of small volumes of liquids, pipettes and burettes are used - pipettes with a stopcock. There are two types of pipettes: 1) “for filling” - the zero mark is at the top and 2) “for pouring” - the upper mark indicates the maximum volume. Rubber balloons and medical bulbs are used to fill pipettes. Under no circumstances should you suck organic liquids into the pipette with your mouth! Glass laboratory equipment also includes connecting elements, funnels, droppers, alcohol lamps, water jet pumps, desiccators, refrigerators, and reflux condensers. The connecting elements (Fig. 1.6) are intended for assembly on thin sections of various laboratory installations. Rice. 1.6. The most important connecting elements: a) transitions, b) allongs, c) nozzles, d) connecting tubes, e) valves Funnels (Fig. 1.7) are used for pouring, filtering and separating liquids. Rice. 1.7. Funnels: a) laboratory, b) filter with a soldered glass filter, c) dividing, d) drip with a side tube to equalize pressure Laboratory funnels are used for pouring liquids into narrow-necked vessels and for filtering solutions through a folded paper filter. Funnels with glass filters are usually used to filter liquids that destroy paper filters. Separating funnels are designed to separate immiscible liquids during the extraction and purification of substances. Dropping funnels are used for the controlled addition of liquid reagents during synthesis, they are similar to separating funnels, they usually have a longer tube outlet, and the tap is located under the reservoir itself, their maximum capacity does not exceed 0.5 liters. Desiccators (Fig. 1.8) are used for drying substances under vacuum and for storing hygroscopic substances. Rice. 1.8. Desiccators: a) vacuum desiccator, b) regular Cups or glasses with substances to be dried are placed in the cells of porcelain liners, and a moisture absorbent substance is placed at the bottom of the desiccator. Refrigerators (Fig. 1.9) are used for cooling and condensing vapors. Air coolers are used for boiling and distilling high-boiling (bp›1600C) liquids; ambient air serves as the cooling agent. Water-cooled refrigerators differ from air-cooled refrigerators in the presence of a water jacket (the cooling agent is water). Water cooling used for condensing vapors and distilling substances with a boiling point of 1600C, and in the range of 120-1600C the cooling agent is static water, and below 1200C - running water. The Liebig refrigerator is used for the distillation of liquids; ball and spiral refrigerators are most applicable as reflux refrigerators for boiling liquids, since they have a large cooling surface. Rice. 1.9. Refrigerators and reflux condenser: a) air, b) with a straight tube (Liebig), c) ball, d) spiral, e) Dimroth, f) reflux condenser Dephlegmators serve for more thorough separation of mixture fractions during its fractional (fractional) distillation. In laboratory practice, porcelain dishes are used for work involving heating (Fig. 1.10). Rice. 1.10. China: a) evaporation cup, b) Buchner funnel, c) crucible, d) mortar and pestle, e) spoon, f) glass, g) burning boat, h) spatula To filter and wash sediments under vacuum, porcelain Nutsch filters - Buchner funnels - are used. Mortars and pestles are designed for grinding and mixing solid and viscous substances. To assemble and secure various instruments in a chemical laboratory, tripods with sets of rings, holders (legs) and clamps are used (Fig. 1.11). Rice. 1.11. Laboratory stand (a) with a set of components: b) rings, c) clamps, d) holder To fix the test tubes, use racks made of of stainless steel, aluminum or plastic alloys, as well as manual holders (Fig. 1.12). Rice. 1.12. Tripod(s) and hand holders for test tubes (b) The tightness of the connections between the components of laboratory instruments is achieved using ground joints (Fig. 1.13) and rubber or plastic plugs. Plugs are selected according to numbers that are equal to the inner diameter of the neck of the vessel or tube opening being closed. Rice. 1.13. Cone sections: a) cores, b) coupling The most universal and reliable way to seal a laboratory device is to connect its individual parts using cone sections by connecting the outer surface of the core to the inner surface of the coupling. I.3 BASIC OPERATIONS WHEN WORKING IN AN ORGANIC CHEMISTRY LABORATORY Qualified performance of practical work by an experimental chemist is impossible without knowledge of the techniques for carrying out basic operations. Therefore, it is necessary to study and master the most frequently used operations in the laboratory of organic chemistry: heating, cooling, dissolving, drying, grinding, mixing, etc. correct execution necessary to ensure safe working conditions. I.3.1 HEATING One of the conditions for the occurrence chemical reactions in a given direction is strict adherence to a certain temperature regime. Basic organic reactions are non-ionic and proceed slowly, so they are often carried out by heating, which helps to increase the reaction rate - the reaction rate when heated by 100C increases by 2-4 times (van't Hoff's rule). For heating, various burners, electric heating devices, water steam, etc. are used. The choice of heating device is carried out taking into account the properties of the solvent, reacting substances and the temperature at which the reaction should be carried out. Burners are gas or liquid (alcohol) (Fig. 1.14). For rapid heating to relatively high temperatures (≈5000C), Bunsen and Tekla gas burners are used. These burners are a metal tube mounted on a metal stand, in the lower part of which there are holes with devices for adjusting the air supply. An alcohol burner is a thick-walled glass reservoir through the neck of which a thread wick or cotton swab is pulled. The neck is covered with a metal or ground glass cap. Fig.1.14. Burners: a) alcohol, b) gas Bunsen, c) gas Teklu The most widely used electric heating devices are mantle heaters, stoves, drying cabinets, muffles, crucibles, shaft furnaces and baths. When used for heating, electric stoves and burners may cause local overheating and partial decomposition of organic matter. To increase heating uniformity above 1000C, asbestos meshes and electric mantle heaters made of fiberglass with woven electric spirals are used (Fig. 1.15). To avoid overheating of the reaction mixture, the burner flame should not extend beyond the asbestos circle on the grid. When working with explosive, flammable substances (ether, acetone, benzene, etc.), various types of heating baths are used to prevent local overheating. The heat-conducting medium in heating baths is air, sand, water, organic liquids, metals, molten salts, etc. When choosing a certain type of bath, the properties of the reaction mixture and the temperature regime, which must be maintained for a long time, are taken into account. The level of the heated substance in the dish must correspond to the level of the bath coolant. To slightly increase the uniformity of heating, air baths are used - a Babo funnel with a gas burner (Fig. 1.16). The maximum temperature achieved when using an electrically heated air bath is 2500C. Rice. 1.15. Electric mantle heater Fig. 1.16. Funnel Babo Sand baths equipped with electric or gas burners have great thermal inertia, allowing them to maintain temperatures up to 4000C. The dishes with the substances are placed to a depth of 2-5 cm in sifted sand, pre-calcined from organic impurities. If the experiment requires maintaining a temperature not exceeding 1000C, boiling water baths are used. The container with flammable substances is gradually immersed in a preheated water bath, eliminating sources of heating. Using a thermometer, monitor the temperature of the mixture and, if necessary, change the cooled water to hot. Water baths should not be used when experimenting with potassium or sodium metal. When distilling highly volatile, flammable substances (petroleum ether, diethyl ether, etc.), steam baths are used. Oil baths have a relatively high thermal inertia and are used for heating in the range of 100-2500C. The maximum temperature achieved depends on the type of coolant (glycerin - up to 2000C, paraffin - up to 2200C). It should be remembered that when water gets in, heated oils foam and splash, so a filter paper cuff is placed on the lower end of the reflux condenser. To prevent ignition of coolant vapors when overheated, the bath is placed in a fume hood, covered with asbestos cardboard, or cold oil is added to the bath. Under no circumstances should you extinguish with water or sand! The temperature is measured with a thermometer placed in the bath at the level of the bottom of the reaction flask; the thermometer should not touch the flask, bottom or walls of the bath. Metal baths are used for heating in the range of 200-4000C; a more intense increase in temperature causes rapid oxidation of the metal surface. Low-melting alloys Wood (Bi:Pb:Sn = 4:2:1) with tm = 710C, Rose (Bi:Pb:Sn = 9:1:1) with tm = 940C are used as coolant. The thermometer and vessels are placed after melting and removed before the coolant solidifies. To maintain the temperature for a long time in a given range, thermostats are used (Fig. 1.17). Rice. 1.17. Thermostats: a) ultrathermostat UT-15, b) microthermostat MT-0.3 It should be remembered that local overheating of liquids above their boiling point can lead to an explosion. To avoid this, long glass capillaries sealed on one side with the open end down are immersed in a cold liquid or small pieces of fired unglazed porcelain or brick are placed, the so-called “boilers”. When heated, they release small air bubbles, which provide mixing and promote uniform boiling. “Kettles” are used one-time, since when cooled, the liquid fills their pores. I.3.2 COOLING When carrying out many chemical works, there is sometimes a need to cool the reaction mixture. This operation is used to accelerate crystallization, separate products with different solubilities, etc. In exothermic reactions, the release of a significant amount of heat can lead to overheating of the reaction mixture, and, consequently, cause a low yield of the final product. In these cases, a decrease in temperature is necessary. The amount of heat rejected and the required temperature determine the choice of coolant. Water is a simple, cheap and heat-intensive agent. The reaction vessel is cooled under running water running water, or periodically immersing in cold water. Circulating cold water is used to cool and condense vapors in refrigerator jackets. When the vapor temperature rises above 1500C, water coolers should not be used, since the glass may crack due to a sharp temperature change. Crushed ice is used to cool to 00C. A mixture consisting of ice and a small amount of water has a more effective cooling effect, since greater contact is achieved with the walls of the flask or test tube. If the presence of water does not interfere with the reaction, it is convenient to keep the temperature low by adding pieces of ice directly to the reaction mixture The use of special mixtures (Table 1.1) with which cooling baths are filled makes it possible to achieve temperatures close to 00C and below. Table 1.1. Cooling mixtures The components of the mixed-quality ratio of animal temperature, 0CH2O, CH3COONA100: 85-4.7H2O, NH4CL100: 30-5.1H2O, Nano3100: 75-5.3H2O, Na2S2O3.5H2O100: 110-8.0H2O, CACL2100: 250 ), CaCl2.6H2O100:41-9.0Ice (snow), Na2S2O3.5H2O100:67.5-11.0H2O, NH4Cl, NH4NO3100:33:33-12.4H2O, CaCl2.6H2O100:250-12.4H2O, NH4NO3100 :60-13.6Ice (snow), KCl100:30-15.8Ice (snow), NH4NO3100:60-17.3H2O, NH4SCN100:133-18.0Ice (snow), NaNO3100:59-18.5Ice (snow) , NaСl (tech.)100:33-20.0H2O, NH4Cl, NH4NO3100:100:100-25.0Ice (snow), KCl (tech.)100:100-30.0Ice (snow), conc. HCl (cooled to 00C) 100: 100-37.0 Ice (snow), NaCl (tech.) 100: 125-40.3 Ice (snow), CaCl2.6H2O100: 143-55.0 By adding solid carbon monoxide (IV) (“dry ice”) to individual solvents (acetone, ether, etc.), a temperature decrease below -700C is achieved. If long-term cooling is required, refrigerated cabinets are used. To avoid metal corrosion upon contact with a mixture of aggressive vapors and condensed moisture, and to prevent an explosion of organic solvent vapors, containers in the refrigerator are tightly sealed. I.3.3 GRINDING Grinding - destruction solids with the formation of particles of material. Grinding is used to perform many operations: in obtaining a homogeneous mass of solids, in extraction, taking an average sample, etc. One of the decisive factors determining the rate of a heterogeneous reaction is the surface area of the solid phase and the possibility of its contact with a liquid medium. Grinding increases the reactivity of compounds. The main characteristics of the grinding process are the change in dispersion and the degree of grinding. The degree of grinding is the ratio of the average size of pieces of the source material to the average particle size of the crushed material. Depending on the purpose of grinding, crushing (obtaining a lump product of the required size) and grinding (increasing the dispersion of solid material, giving particles a certain shape) are distinguished. Depending on the size of the crushed product, coarse (300-100 mm), medium (100-25 mm), fine (25-1 mm) crushing and coarse (1000-500 microns), medium (500-100 microns), fine ( 100-40 microns), ultra-fine (less than 40 microns) grinding. Solids are crushed manually or mechanically. The choice of grinding method and means is determined by the mechanical and chemical properties of the material being processed and the required degree of dispersion. For immediate chemical exposure fine and ultrafine grinding is desirable. Materials for extraction and steam distillation may be limited to coarse grinding. Grinding is carried out in mortars (Fig. 1.18) made from various materials. Metal mortars are used to grind pieces or large crystals of substances. Substances less solid than phosphorus are ground in porcelain devices. Agate mortars are used for the preparation of analytical samples, since the mineral is very hard, abrases little and does not clog the substance being ground. The size of the mortar is chosen in accordance with the amount of working material, which should not occupy more than 1/3 of its volume. Grinding is carried out with rotational movements, from time to time cleaning parts of the mortar and pestle with a spatula and collecting the substance towards the center. It is more advisable to process substances in small portions. If the material smears and sticks, before grinding it is mixed with silicon (IV) oxide, broken glass, and pumice. Rice. 1.18. Mortars: a) agate, b) for grinding dusty and toxic substances. Work with dusty and toxic substances in a fume hood, using special mortars with dust-proof devices or covering a regular mortar with polyethylene with a hole for the pestle. In laboratories, mechanical grinders, crushers, mills and homogenizers are also used to grind substances. It should be remembered that grinding substances increases their chemical activity, so the possibility of an explosion cannot be ruled out. For safety reasons, before handling large quantities of unknown substances, it is necessary to ensure that there is no risk of explosion on a small sample. I.3.4 MIXING Mixing is a method of obtaining homogeneous mixtures. This operation for solid bulk substances is defined by the term mixing, for liquid ones - mixing. Mixing is done manually and mechanically. The operation is carried out using a mixing device or shaking. Periodic shaking is used if the use of stirrers is difficult, if substances are not added, cooled, or heated during the operation. If there is a significant release of gases and vapors, shaking should not be used. The physical state of the mixed substances determines the choice of method and equipment for its implementation. When working with small quantities of solids and liquids in fast reactions, manual stirring in a beaker using a glass rod or shaking the vessel is sometimes sufficient. The flasks are rotated, held by the neck, and the closed vessels are turned over several times. It should be remembered that in vessels with low-boiling liquids, pressure increases when stirred, so the plugs in them must be held. When working with viscous liquids, large quantities of substances, or carrying out reactions over a long period of time, mechanical stirring is used. The operation can be carried out using magnetic, vibrating stirrers, as well as stirrers rotating by electric drive. Under normal conditions (at atmospheric pressure, ambient temperature, in the presence of air moisture), stirring is carried out in open wide-necked vessels, thick- or thin-walled beakers, titration flasks, wide-necked test tubes, and special flasks. This utensil allows you to simultaneously use stirrers, thermometers, dropping funnels, etc. Mechanical stirring is effectively carried out using glass stirrers (Fig. 1.19), which can be easily made from thick sticks or tubes with a diameter of 4-10 mm. They are given different configurations depending on the shape, size of the vessel and the width of its neck. Depending on the mixing method, different types of mixers are used (Fig. 1.20). Open, cylindrical, wide-necked vessels accommodate more efficient flat, propeller, or screw stirrers. Rice. 1.19. Glass stirrers Fig. 1.20. Stirrers For narrow-necked dishes, stirrers with glass or fluoroplastic blades are used, which tilt outward under the influence of centrifugal forces. They are not suitable for intensive mixing. At high speeds, this type of stirrer can easily break and break the reaction vessels. Propeller and centrifugal mixers are not suitable for heavy, solid materials (eg molten sodium). In these cases, it is convenient to use a Gershberg stirrer with a glass rod and wire blades (d = 1-2 mm), which is easily inserted through the narrow neck of the reaction vessel. During operation, its blades take on the shape of a flask and easily slide along the walls without leaving scratches. To work with substances that adhere to the walls of narrow-necked flasks, scraper-type stirrers are used, but they cannot be used while simultaneously introducing a thermometer into the flask. Mixing in large volumes is carried out using metal paddle and centrifugal mixers. When working in a deep vacuum and with small volumes of low-viscosity substances (during liquid-liquid extraction, electrolysis, titration), it is convenient to use magnetic stirrers (Fig. 1.21). They consist of a motor with a rotating magnet and a rod placed in a reaction vessel. Under the influence of the magnetic field created by the rotor of the electric motor, the rod begins to move. Magnetic stirrers can be combined with flat electric heaters, but the low stability of magnets when heated should be taken into account. The advantages of this type of mixer are the ability to use equipment without special preparation, placing the stirring rod in closed devices (sealed vessels). Fig.1.21. Magnetic stirrer To mix liquids with gases, for immiscible liquids, vibrating mixers are installed, in which a membrane with a glass or steel plate is driven by an alternating electromagnetic field. This method is effective for the formation of thin emulsions. When carrying out many reactions requiring mixing, there is a need to prevent the leakage of volatile substances, maintain high or low pressure, isolate the contents of the vessel from external environment(penetration of air and water vapor). Tightness is ensured by seals or special devices- valves, and the reliable operation of the seals depends, in turn, on the supply of lubricating fluid (water, oil, glycerin, etc.) To ensure uniform, silent operation of the mixers, it is necessary to fix the position of their axis. The stands used for mounting must be sufficiently stationary, and the stirrer rod must not oscillate when rotating. Before starting work, turning the mixer manually, you need to make sure how easily it rotates and whether it touches the walls of the reactor, thermometer and other parts of the device. Obtaining a homogeneous mass of solid bulk solid materials from individual substances by mixing them can be carried out simultaneously with chemical transformations, grinding, heating, cooling, and moistening. In industrial conditions, special devices of periodic and continuous operation are used for this purpose. When mixing several solids, it is necessary that they have, if possible, the smallest particles of the same size. In laboratory conditions, crushed substances can be poured into the middle of a square sheet and mixed by rolling, lifting its ends one by one. Solids mix well when repeatedly sifted through sieves, the diameter of the holes of which exceeds the diameter of the working particles by 2-3 times. Mixing can also be carried out by repeatedly pouring substances from one vessel into another, with the containers being filled with the mixed substances to no more than half the volume. All devices intended for grinding (mortars, mills, etc.) can also be used for mixing. I.3.5 DRYING In organic chemistry, some reactions can only be carried out in the absence of moisture, so preliminary drying of the starting substances is necessary. Drying is the process of freeing a substance, regardless of its state of aggregation, from liquid impurities. Drying can be carried out by physical and chemical methods. The physical method consists of passing dry gas (air) through the substance to be dried, heating it or keeping it in a vacuum, cooling, etc. At chemically drying agents are used. The choice of drying method is determined by the nature of the substance, its state of aggregation, the amount of liquid impurity and the required degree of drying (Table 1.2). Drying is never absolute and depends on the temperature and the drying agent. Drying of gases is carried out by passing them either through a layer of water-absorbing liquid (usually concentrated sulfuric acid) poured into a Drexel wash bottle (Fig. 1.22), or through a layer of granular desiccant placed in a special column or U-shaped tube. An effective way to dry air or gases is through extreme cooling. When current is passed through a trap cooled by a mixture of acetone with dry ice or liquid nitrogen, water freezes out and precipitates on the surface of the trap. Table 1.2. The most common dehumidifiers and their applications Desiccant Substances to be dried Substances for which use is unacceptable P2O5 Neutral and acidic gases, acetylene, carbon disulfide, hydrocarbons and their halogen derivatives, acid solutions Bases, alcohols, ethers, hydrogen chloride, hydrogen fluorideCaH2 Noble gases, hydrocarbons, ethers and esters, ketones, carbon tetrachloride, dimethyl sulfoxide, acetonitrile Be acidic substances, alcohols, ammonia, nitro compounds CaO (sodium lime) Neutral and basic gases, amines, alcohols, ethers Aldehydes, ketones, acidic substances Na metal Ethers, hydrocarbons, tertiary amines Chlorine derivatives of hydrocarbons, alcohols and substances that react with sodium conc. H2SO4 Neutral and acidic gases Unsaturated compounds, alcohols, ketones, bases, hydrogen sulfide, hydrogen iodide NaOH, KOHA Ammonia, amines, ethers, hydrocarbons Aldehydes, ketones, acidic substances anhydrous. K2CO3Acetone, aminesAcidic substancesCaC12Paraffin hydrocarbons, olefins, acetone, ethers, neutral gases, hydrogen chlorideAlcohols, ammonia, aminesanhydrous. Na2SO4, MgSO4 Esters, solutions of substances sensitive to various influences Alcohols, ammonia, aldehydes, ketones Silica gel Various substances Hydrogen fluoride Rice. 1.22. Drying gases: 1) Drexel flask, 2) column with solid desiccant, 3) U-shaped tube, 4) cooled traps: a) coolant, b) Dewar flask Drying liquids is usually accomplished by direct contact with some type of desiccant. The solid desiccant is placed in a flask containing the organic liquid to be dried. It should be noted that the use of too much desiccant may lead to loss of substance as a result of its sorption. Drying solids is carried out in the simplest way, which is as follows: the substance to be dried is placed thin layer onto a sheet of clean filter paper and leave at room temperature. Drying is accelerated if it is carried out under heating, for example in an oven. Small quantities of solids are dried in conventional or vacuum desiccators, which are thick-walled vessels with a ground, ground lid. The polished surfaces of the lid and the desiccator itself must be lubricated. The desiccant is located in the lower part of the desiccator, and the dried substances in bottles or Petri dishes are placed on porcelain partitions. A vacuum desiccator differs from a regular one in that its lid has a tap for connecting to a vacuum. Desiccators are used only for operation at room temperature; they cannot be heated. 4 METHODS FOR ISOLATING AND PURIFYING SUBSTANCES I.4.1 FILTERING The simplest way to separate a liquid from the particles of solid matter contained in it is decantation - draining the liquid from the settled sediment. However, it is difficult to separate the completely liquid phase from the solid phase in this way. This can be achieved by filtration - passing liquid with sediment through a filter material. There are different filter materials and different filtering methods. The most common filter material in the laboratory is filter paper. Paper filters are made from it. The size of the filter is determined by the mass of the sediment, not the volume of the filtered liquid. The filtered sediment should occupy no more than half the filter volume. Before starting work, the filter is moistened with the solvent that is to be filtered. During filtering, the liquid level should be slightly below the top edge of the paper filter. A simple filter is made from a square piece of filter paper (Fig. 1.23.) The filter should fit snugly against the inner surface of the glass funnel. The pleated filter has a larger filtering surface and filters through it faster. If the solution contains strong acids or other organic substances that destroy paper, glass crucibles with a porous glass bottom or glass funnels with porous glass plates sealed into them are used for filtering. Glass filters have a number according to the pore size: the larger the filter number, the smaller the pore cross-section and the smaller the sediments that can be filtered on it. The laboratory uses several filtration methods: simple, vacuum, hot. Rice. 1.23. Filters: Fig. 1.24. Simple filtering ) production of a simple filter, 2) production of a folded filter, 3) filter crucible with a porous plate, 4) funnels with a glass porous plate Simple filtering comes down to using a glass funnel with a paper filter inserted into it (Fig. 1.24). The funnel is inserted into the ring, and a glass or flat-bottomed flask is placed under it to collect the filtered liquid (filtrate). The spout of the funnel should be slightly lowered into the receiver and touch its wall. The filtered liquid is transferred to the filter using a glass rod. To speed up and more completely separate the precipitate from the filtrate, vacuum filtration is used. A porcelain Buchner funnel (Fig. 1.25), which has a flat perforated septum on which a paper filter is placed, is inserted into a flat-bottomed, thick-walled Bunsen flask using a rubber stopper. The filter is cut to fit the bottom of the funnel. The vacuum is created by a water jet pump. If the pressure in the water supply network weakens, water from the pump may enter the device. To avoid this, install a safety bottle. Rice. 1.25. Filtration a) in vacuum: 1) Bunsen flask, 2) Buchner funnel; b) small amounts of substances When carrying out filtration in a vacuum, certain rules must be observed: 1) connecting a water-jet pump and connecting it to the system, 2) wetting the filter with a small amount of the solvent that is supposed to be filtered, 3) adding filter liquid. The precipitate collected on the filter is squeezed out with a glass stopper until the mother solution stops dripping from the funnel. If a whistling sound occurs during filtering, this indicates a loose or broken filter, in which case the filter should be replaced. If the precipitate on the Buchner funnel needs to be washed, then using a three-way tap, first connect the Bunsen flask to the atmosphere, then the precipitate is soaked in the washing liquid and filtered, turning on the vacuum again. After finishing the filtration, first disconnect the entire system from the vacuum, then turn off the water jet pump. Hot solutions usually filter faster than cold solutions because the heated liquid has a lower viscosity. Hot filtering is carried out in glass funnels heated from the outside in one way or another (Fig. 1.26). The simplest method, most applicable for filtering aqueous solutions, is to use a funnel with a shortened tail, which is placed in a glass without a spout with a diameter slightly smaller than the upper edge of the funnel. Pour some water into the bottom of the glass and cover the funnel with a watch glass. The water in the glass is brought to a boil. When the water vapor heats the funnel, the watch glass is removed and the hot filtered mixture is poured into the funnel. During the entire filtering process, the solution in the glass is maintained at a low boil. 1)2)
Rice. 1.26. Funnels for 1) hot filtering: a) with steam heating, b) with hot water heating, c) with electric heating; 2) filtering while cooling I.4.2 CRYSTALLIZATION Crystallization is one of the most important methods for the purification and separation of solids in laboratory and industrial settings. The method is based on the process of formation of crystals from a melt, solution or gas phase. But the substance obtained as a result of crystallization is not always pure enough, so the resulting product is subjected to further purification, which is called recrystallization. When heated, the contaminated substance is dissolved in a suitable solvent to obtain a saturated solution. The hot solution is filtered to remove insoluble impurities, then the filtrate is cooled. When a saturated solution is cooled, the solubility of substances decreases. Part of the solute precipitates as a precipitate, which contains fewer impurities than the original substance. The method is applicable for substances whose solubility increases significantly with increasing temperature. The result of crystallization depends to a large extent on the choice of solvent (Table 1.3). The substance to be purified should dissolve poorly in the selected solvent in the cold and dissolve well at its boiling point. Contaminants must be difficult to dissolve or insoluble in the solvent. The solvent must not react with the solute. It should cause the formation of stable crystals and be easily removed from the surface of the crystals when washed and dried. Table 1.3. Solvents used in recrystallization Properties Class of compounds Solvents Hydrophobic Hydrocarbons, halogen derivatives of hydrocarbons, ethers Hydrocarbons, ether, halogen derivatives of hydrocarbons Amines, esters, nitro compounds Esters Nitriles, ketones, aldehydes Alcohols, dioxane, acetic acid Phenols, amines, alcohols, carboxylic acids, sulfonic acids Alcohol, water Hydroph siltSaltWater When the solvent is selected, the substance is heated with it to a boil, taking all precautions. First, the solvent is taken in a smaller quantity than is necessary to completely dissolve the substance, and then it is added in small portions through a reflux condenser (Fig. 1.27). Rice. 1.27. Crystallization device: ) flask, 2) reflux condenser, 3) bath, 4) boilers If necessary, the solution is decolorized by adding an adsorbent (crushed activated carbon, finely torn filter paper). Before adding adsorbents, the solution should be cooled slightly, since these substances can intensify the boiling process, which will lead to vigorous ejection from the flask. The solute-adsorbent mixture is again heated to boiling and filtered while hot using a conical funnel and a pleated filter. The flask containing the filtrate is left to cool. Gradually, crystals of the test substance fall out of the filtrate. Slow cooling of the filtrate makes it possible to obtain large crystals, while rapid cooling produces small ones. Solid organic substances, when distilling off solvents, may be released in the form of oily liquids, which makes their crystallization difficult. This can be avoided by adding several pure crystals of the crystallizable substance. Rubbing the glass rod against the walls of the vessel also facilitates the crystallization process. PRACTICUM Experiment 1. RECRYSTALLIZATION OF BENZOIC ACID Rea cts: benzoic acid, water Place 1 g of benzoic acid and 50 ml of water in a 100 ml conical flask. The mixture is heated to a boil - benzoic acid completely dissolves. The hot solution is quickly filtered through a pleated filter and the filtrate is poured equally into two flasks. The contents of one flask are quickly cooled under running water tap water or in ice and shaken. Benzoic acid precipitates in the form of small crystals. The solution in another flask is kept at room temperature for 20-25 minutes. Slow crystallization occurs and shiny large lamellar crystals of benzoic acid are formed. The resulting crystals are filtered and dried. Melt=1220C. Experiment 2. RECRYSTALLIZATION OF ACETANILIDE IN ALCOHOL SOLUTION Rea cts: acetanilide, ethyl alcohol 1 g of acetanilide and 5 ml of ethyl alcohol are placed in the flask. The contents of the flask, shaking constantly, are heated in a hot water bath until the mixture begins to boil, achieving complete dissolution of acetanilide. Half of the resulting alcohol solution is poured into a test tube and cooled. Add to the remainder of the hot solution while shaking warm water(12-15 ml) until a slight cloudiness appears, after which the solution is slightly heated until clear and allowed to cool. When the alcohol solution is cooled, no acetanilide precipitate is formed, while crystals are released from the aqueous-alcohol solution with gentle shaking. The solubility of acetanilide in water is much less than in alcohol. Adding water to an alcohol solution reduces the solubility of acetanilide, thereby achieving saturation of the hot solution, upon cooling of which the formation of an abundant crystalline precipitate is observed. Melt=1140C. I.4.3 SUBLIMITATION Sublimation (sublimation) is the process of evaporation of a solid substance followed by condensation of its vapor directly into a solid substance, bypassing the liquid phase. Sublimation is used to purify those organic substances whose crystallization is difficult. To sublimate a small amount of a substance at atmospheric pressure, it is placed in a porcelain cup and covered with a circle of filter paper with small holes made with a needle. An overturned glass funnel is placed on top, the spout of which is tightly closed with a cotton swab (Fig. 1.28). The cup is carefully heated. Vapors of the sublimating substance pass through the holes in the filter and condense on the inner walls of the funnel. The partition protects crystals of pure substance from falling into the heating zone. Rice. 1.28. Devices for sublimation: a) at atmospheric pressure, b) in vacuum The rate of sublimation is inversely proportional to external pressure. To increase the speed of the process, you can increase the temperature, pass a weak current of air over the substance, or lower the pressure. Carrying out sublimation under vacuum also allows one to lower the temperature, which is very important in the case of decomposing substances. As with any evaporation, the rate of sublimation is proportional to the area of the evaporated surface, so the substance must be thoroughly crushed before sublimation and not allowed to melt. The disadvantages of sublimation are the relatively long process duration and limited application. However, this purification method compares favorably with recrystallization in the absence of contact of the substance with the solvent and in the high final yield. PRACTICUM Experiment 3. PURIFICATION OF NAPHTHALENE AND ANTHRAQUINONE BY SUBLIMATION METHOD REACTIVES: naphthalene, anthraquinone Naphthalene (anthraquinone) is placed in a porcelain cup and the sublimation system is assembled. After sublimation, the precipitation of purified naphthalene (anthraquinone) crystals on the filter paper is observed. Melt=80.30C. I.4.4 DISTILLATION Distillation is the process of separating multicomponent liquid mixtures into separate fractions that differ in composition. Distillation is used to purify and separate volatile substances, usually liquids. Distillation is applicable only when the substance being distilled is stable at the boiling point. Depending on the process conditions, simple, fractional distillation, steam distillation and vacuum distillation are distinguished. Simple distillation is effective in cases where the boiling temperatures of the substances included in the mixture differ significantly (by at least 800C). A typical apparatus for simple distillation at atmospheric pressure consists of a round-bottomed long-neck flask with a tap (Wurtz flask), direct refrigerator, allonge and receiver flask (Fig. 1.29). Rice. 1.29. Device for simple distillation of liquid substances: ) Bunsen burner, 2) ring with clamp and asbestos mesh, 3) distillation flask (Wurtz flask), 4) foot with clamp, 5) thermometer, 6) stands, 7) Liebig refrigerator, 8) allonge, 9) receiving flask A thermometer is inserted into the neck of the Wurtz flask so that the mercury ball of the thermometer is 0.5 cm below the hole in the outlet tube of the Wurtz flask. Depending on the boiling point of the liquid, water (up to 110-1200C) or air (above 1200C) refrigerators are used. The liquid to be distilled is introduced into the Wurtz flask through a funnel, the spout of which should be below the outlet of the Wurtz flask. In this case, the distillation flask is filled to no more than 2/3 of the volume. To prevent overheating and ensure that the liquid boils evenly, so-called “boilers” are introduced into the distillation flask - small pieces of an unglazed plate or capillaries with the open end down. The choice of heating device depends on the boiling point of the liquid being distilled, its flammability and explosiveness. For uniform heating, it is best to place the distillation flask in a suitable bath. The distillation is carried out at such a speed that no more than two drops of distillation liquid (distillate) flow into the receiver within a second. Distillation cannot be carried out dry. There should always be at least 2-3 ml of liquid left in the flask. During the entire distillation of an individual substance, the temperature of the vapor must remain constant. If the temperature rises during distillation, it means a mixture of substances is being distilled. At the initial point of distillation, the temperature is usually lower than expected. This may be due either to the inertia of the mercury thermometer, or to the fact that more volatile impurities are distilled off at the first moment. Therefore, the first portions of the distillate (before reaching a constant distillation temperature) are collected separately and discarded. After the temperature has established, the main fraction of the substance is collected. As soon as the temperature begins to increase again, the receiver is changed to collect another fraction. The boiling point of a substance depends on pressure. If distillation is carried out at residual pressure, then the boiling point of the distilled substance will differ from the reference one. In this regard, it is always necessary to record the value atmospheric pressure, at which distillation is carried out. Fractional distillation is used to separate miscible liquids boiling at different temperatures. Fractional distillation is carried out in a device that is fundamentally the same as a device for simple distillation, but equipped with a reflux condenser (Fig. 1.30). Rice. 1.30. Device for fractional distillation: ) distillation flask, 2) reflux condenser, 3) thermometer, 4) refrigerator, 5) allonge with calcium chloride tube, 6) receiver The resulting vapor condensate is collected in the form of several fractions. The greater the number of fractions, the more effective the separation will be. Each of the resulting fractions contains a mixture of substances, but the first fractions are enriched with a more volatile component, and the latter - with a less volatile one. To increase the efficiency of mixture separation and, consequently, reduce the number of repeated distillations, reflux condensers are used. The essence of the action of a reflux condenser is that when vapors pass through it, they are cooled on the walls of the reflux condenser and partial condensation occurs, primarily of the higher-boiling component. The condensing vapors in the form of a liquid (reflux) flow back into the distillation flask (hence the name reflux condenser). The process is repeated many times and this ensures high separation efficiency. To prevent contact of the distilled substance with air moisture, an allonge with a tube (outlet tube) is used. The allonge is hermetically connected to the receiver flask, and the tube is connected to a calcium chloride tube. Calcium chloride tubes prevent moisture vapor from entering the interior of the device, while ensuring communication with the atmosphere. Steam distillation is based on the fact that high-boiling substances that are immiscible or slightly miscible with water, when steam is passed through them, evaporate and condense together in the refrigerator. The distillate collected in the receiver in the form of two layers of immiscible liquids is then separated in a separating funnel. Using steam distillation, it is possible to distill substances boiling much higher at a temperature of 1000C (Table 1.4). Table 1.4. Some substances distilled with steam Substance Boiling point, 0С Content of substance in distillate, % Pure substance Mixture of substance with water vapor Phenol 182.098.620.6 Aniline 184.498.523.1o-Cresol 190.198.819.3 Nitrobenzene 210.999.315.3 Naphthalene 218.299.314.4 Brombene zol156,295,561.0 With water steam you can distill organic substances that are practically immiscible with water or have limited miscibility with it at boiling point, but do not react chemically. Steam distillation is carried out in a device consisting of a steam generator, a distillation flask, a refrigerator and a receiver (Fig. 1.31). Rice. 1.31. Steam distillation apparatus: ) steam generator, 2) distillation flask, 3) refrigerator, 4) allonge, 5) receiver The steam generator is a metal vessel equipped with a water measuring glass and a safety tube. The tube should reach almost to the bottom and serves to equalize the pressure. Distillation begins by bringing the water in the steam generator to a boil and, closing the clamp on the tee, directing a stream of steam into the distillation flask. The steam passes through the distilled mixture and, carrying with it the distilled component of the mixture, enters the refrigerator and then in the form of condensate into the receiver. Typically, the distillation flask is also heated to prevent water vapor from condensing in it. Distillation is carried out until the distillate ceases to separate into two phases. When only water is distilled, open the clamp on the tee and only then stop heating the steam generator. Purifying organic matter by steam distillation often produces better results than conventional distillation. It is especially effective in cases where the product to be cleaned is heavily contaminated with resinous substances. When it is necessary to lower the boiling point to reduce the risk of decomposition of the distilled substance, it is advisable to carry out distillation in a vacuum. To approximate the boiling point of a substance in a vacuum, they are guided by the following rule: when the external pressure is halved, the boiling point of the substance decreases by 15-200C. The device for distillation in vacuum (Fig. 1.32) differs from the device for simple distillation in that a flask with a Claisen nozzle, equipped with a capillary with a very small internal diameter, is used as a distillation flask. Through this capillary, air enters the evacuated system in a thin stream, bubbling through the liquid in the distillation flask, and thus the capillary plays the same role as boilers in simple distillation. The capillary should reach almost to the very bottom of the flask. A piece of rubber vacuum hose with a thin wire inserted, equipped with a Hoffmann screw clamp for fine adjustment of the speed of air bubbles passing through it, is placed on top of it. The selection of fractions during fractional vacuum distillation is carried out using special allonges of various designs, called “spiders”. "Spider" allows you to change the receiver without disconnecting the system from the vacuum. The system for vacuum distillation must include a safety bottle and a pressure gauge. If the device is assembled on ground sections, all of them must be pre-lubricated with vacuum grease. The substance to be distilled is placed in a Claisen flask, the system is connected to a vacuum, and the tightness of the system is checked using a pressure gauge. Rice. 1.32. Vacuum distillation apparatus: ) distillation flask, 2) capillary, 3) thermometer, 4) refrigerator, 5) allonge (“spider”), 7) safety bottle, 8) pressure gauge Once the desired vacuum is reached, heating of the flask begins. During distillation, it is necessary to monitor temperature and pressure. At the end of the distillation, the heat source is first removed, the flask is allowed to cool slightly, and only then the device is slowly connected to the atmosphere. To do this, first fully open the Hoffmann clamp on the capillary, then open the three-way valve and only then turn off the pump. Carefully opening the pressure gauge tap, slowly let air into it. PRACTICUM Experiment 4. SIMPLE DISTILLATION OF LIQUID ORGANIC SUBSTANCES Rea cts: acetone, chloroform, dichloroethane, benzene Assemble a device for simple distillation (Fig. 1.29) and carry out the distillation of one of the following liquids: acetone (560C), chloroform (610C), dichloroethane (83.70C), benzene (800C). Experiment 5. FRACTIONAL DISTILLATION OF LIQUID ORGANIC SUBSTANCES REACTIONS: mixtures of aniline-chloroform, chloroform-xylene, benzene-xylene Assemble the device for fractional distillation (Fig. 1.30) and carry out the distillation of one of the following mixtures: mixtures of aniline (1840C)-chloroform (610C), chloroform (610C)-m-xylene (1390C), benzene (800C)-m-xylene ( 1390С). Experiment 6. DISTILLATION OF LIQUID ORGANIC SUBSTANCES WITH WATER VAPOR Rea cts: aniline Assemble a device for steam distillation (Fig. 1.31) and carry out the distillation of aniline. Aniline is separated from water using a separating funnel, dried over calcium chloride, poured from calcium chloride into a dry flask and distilled by simple distillation. I.5 The most important physical constants Each organic substance is characterized by constant physical properties under certain conditions (temperature and pressure). In the chemical literature, the following physical properties are most often given: melting point (melting point), boiling point (boiling point), refractive index, specific rotation, density, viscosity, UV, IR, and PMR spectra. By determining the most important physical constants of an unknown compound and comparing them with literature data, it is possible to identify the unknown substance (establish its structure) and prove its purity. I.5.1 MELTING TEMPERATURE The term “melting point” refers to the temperature range in which the transformation of a solid into a liquid occurs. The initial melting temperature is the temperature at which the first liquid drop appears. The final melting point is the one at which all of the solid changes to liquid. The difference between the final and initial melting temperatures should be no more than 10C. For pure organic substances, the melting point must be clear. To determine the melting point, a small amount of the test substance is ground in a mortar and placed in a capillary sealed at one end, tapping the open end, a little substance is taken into it and thrown with the sealed end down into a long glass tube, standing vertically on a rigid surface to transfer the substance to the sealed end. A capillary filled with a substance is attached to the thermometer using a rubber ring so that the substance is at the level of the middle of the thermometer ball. A thermometer with one or more capillaries is fixed in a clean, dry test tube using a stopper that has a cutout opposite the thermometer scale (Fig. 1.33). It should not come into contact with the walls of the test tube, and its reservoir should be 0.5-1 cm above the bottom of the test tube. Rice. 1.33. Melting point determination device: ) round-bottomed flask, 2) capillary with a substance, 3) test tube, 4) extensions for holding the test tube, 5) hole, 6) stopper with thermometer The test tube with the thermometer is fixed vertically in the leg of the tripod and a glass (flask) with petroleum jelly is placed under it on a ring with a mesh. The liquid level should be above the thermometer reservoir, and the test tube should be at a distance of no less than 0.5-1 cm from the bottom of the glass (flask). The assembled device is slowly heated, carefully monitoring the temperature increase and the state of the substance in the capillary. While observing the substance in the capillary, color changes, decomposition, sticking, sintering, etc. are noted and recorded. When the column of substance begins to noticeably shrink and “get wet,” heating is stopped. The beginning of melting is considered to be the appearance of the first drop in the capillary, and the end is the disappearance of the last crystals. Some organic substances do not have a characteristic transition point from solid to liquid and, when heated quickly and strongly, become carbonized and volatilize. These substances include acetylsalicylic acid (aspirin), the melting point of which is determined differently. The capillary is filled, as usual, with ground powder of the substance under study, attached to the thermometer, but a thermometer without the substance is placed in the device. When the temperature reaches 123-1250C. insert a thermometer with a capillary into the device and continue, as usual, determining the melting point. PRACTICUM Experiment 7. DETERMINATION OF THE MELTING TEMPERATURE OF ORGANIC SOLID SUBSTANCES REACTIVES: salol, naphthalene, acetanilide, benzoic acid, aspirin A device is assembled to determine the melting point (Fig. 1.33.) and the melting point of the following substances is determined: salol (420C), naphthalene (80.30C), acetanilide (1140C), benzoic acid (1220C), aspirin (1350C). The obtained data is compared with reference data. I.5.2 BOILING POINT Boiling point is the temperature at which a substance transitions from a liquid state to a gaseous state. The boiling point of the substance under study can be determined in two ways: 1) by distillation, 2) by the micromethod according to Sivolobov. To perform the first method of determining the boiling point, assemble a device for simple distillation (Fig. 1.30) and carry out the distillation of the substance under study. When the first drop of distillate enters the receiver, the temperature is noted and it is conventionally considered the initial boiling point. The pure substance is distilled almost completely within 1-20C. It should be remembered that for connections with bp.<1500С используют водяной холодильник, при Т.кип.>The 1500C water cooler is replaced with an air cooler (glass tube of the same length). To determine the boiling point of a small amount of liquid, the Sivolobov micromethod is used. A drop of liquid is placed in a thin-walled glass tube with a diameter of 2.5-3 mm sealed at one end. A capillary is lowered into it with its open end, which is sealed in the upper part at a distance of 1 cm from the open end. Attach the tube to a thermometer (Fig. 1.34) and heat it in a device to determine the melting point. Rice. 1.34. Sivolobov's device As soon as the liquid under test in the capillary is heated to a temperature slightly above its boiling point, bubbles will continuously begin to emerge from the capillary. To accurately establish the boiling point, further heating is stopped and the temperature at which the emission of bubbles stops is noted. PRACTICUM Experiment 8. DETERMINATION OF THE BOILING TEMPERATURE OF LIQUID ORGANIC SUBSTANCES Rea cts: chloroform, dichloroethane The boiling point of chloroform and dichloroethane is determined by simple distillation and the Sivolobov micromethod. There are two main methods for determining the structure of organic compounds. If the substance under study has been previously studied, then to prove its structure, physical constants and spectral characteristics are determined, which are compared with literature data. If an organic compound is obtained for the first time, it is first subjected to qualitative and quantitative elemental analysis, and then its molecular weight is determined. Based on molecular weight and elemental analysis data, the molecular formula of a substance is determined. Determine the structure of the carbon skeleton, the nature and position of atoms in space. For these purposes, chemical and physical methods are used. Based on the data obtained, a structural or stereochemical formula is derived. II.1 QUALITATIVE ELEMENTAL ANALYSIS OF ORGANIC COMPOUNDS Qualitative elemental analysis is a set of methods that make it possible to determine what elements an organic compound consists of. To determine the elemental composition, organic matter is subjected to destruction, converted into simple inorganic matter by complete combustion, oxidation or mineralization (alloying with alkali metals), which is then examined by analytical methods. PRACTICUM Experiment 9. DETECTION OF CARBON REACTIVES: sucrose, sodium chloride, concentrated sulfuric acid Place a few crystals of sucrose (or any other organic substance) on the tip of a scalpel or metal spatula and gently heat it in the flame of a burner. The sucrose melts, darkens, chars and burns completely. For comparison, a similar experiment is carried out with sodium chloride. Sodium chloride, introduced at the tip of a scalpel into the burner flame, does not undergo any changes even with prolonged heating. A small amount of finely ground sucrose powder is placed in a porcelain cup and a few drops of concentrated sulfuric acid are added - the white powder darkens and chars. These experiments confirm that sucrose contains carbon, that is, it is an organic substance that easily changes when heated and under the influence of concentrated sulfuric acid. Experiment 10. DETECTION OF CARBON AND HYDROGEN REACTIVES: glucose, copper (II) oxide, anhydrous copper (II) sulfate, barite water The method is based on the oxidation reaction of organic matter with copper (II) oxide powder. As a result of oxidation, the carbon included in the composition of the analyzed substance forms carbon dioxide, and hydrogen - water. Carbon is determined qualitatively by the formation of a white precipitate of barium carbonate when carbon dioxide reacts with barite water. Hydrogen is detected by the formation of CuSO4 crystal hydrate. 5H2O is blue. Copper (II) oxide powder is placed into a test tube at a height of 10 mm, an equal amount of organic matter is added and mixed thoroughly. A small ball of cotton wool is placed in the upper part of the test tube, onto which a thin layer of white anhydrous copper (II) sulfate powder is poured. The test tube is closed with a stopper with a gas outlet tube so that one end almost touches the cotton wool, and the other is immersed in a second test tube with 1 ml of barite water. Heat carefully in the burner flame first upper layer a mixture of the substance with copper (II) oxide, then the lower one. In the presence of carbon, turbidity of barite water is observed due to the formation of barium carbonate precipitate. After a precipitate appears, test tube 3 is removed, and test tube 1 continues to be heated until the water vapor reaches anhydrous copper (II) sulfate. In the presence of water, a change in the color of copper (II) sulfate crystals is observed due to the formation of CuSO4 crystal hydrate. 5H2O. C6H12O6 + CuO ¾® Cu + CO2 + H2O CuSO4 + H2O ¾® СuSO4. 5H2O Ba(OH)2 + CO2 ¾® BaCO3 + H2O Experiment 11. DETECTION OF HALOGENS A. Beilstein reaction Rea cts: chloroform, copper wire The method for detecting halogens (chlorine, bromine, iodine) in organic compounds is based on the ability of copper (II) oxide to decompose halogen-containing organic compounds at high temperatures to form copper (II) halides: CuO ¾® CuHal2 + CO2 + H2O The copper wire is pre-cleaned: moistened in hydrochloric acid and calcined in a burner flame until the color of the flame disappears. In this case, the copper becomes covered with a black coating of oxide. After the wire has cooled, a small amount of the test substance is placed on the tip of the wire, folded into a loop, and introduced into the burner flame. In the presence of halogen, the flame turns a beautiful green color. B. Method of A.V. Stepanov Rea cts: chloroform, ethyl alcohol, sodium metal, % silver nitrate solution The method is based on the conversion of a covalently bonded halogen in an organic compound to an ionic state by the action of sodium metal in an alcohol solution. 4 drops of chloroform, 2-3 ml of ethanol and a piece of sodium metal (2x2 mm) are placed in a test tube. The reaction mixture begins to boil violently boil (hydrogen release), after which the test tube is placed in a glass of water to cool. С2H5OH + Na ¾® C2H5ONa + H + 2H ¾® CH4 + HCl After the release of hydrogen bubbles, check whether metallic sodium has completely reacted by adding 3-5 drops of ethanol. After making sure that there is no sodium, add 3-4 ml of water and acidify with a 20% solution of nitric acid to an acidic litmus solution. With the subsequent addition of 1-2 drops of a 1% solution of silver nitrate, the appearance of an abundant precipitate of silver chloride is observed: Ag+ ¾® AgCl ¯
The speed and completeness of the elimination of the halogen atom under these conditions is explained by the simultaneous effect of sodium alkoxide and hydrogen on chloroform at the time of separation. С2H5ONa + Н2О ¾® C2H5OH + NaOH NaOH + HCl ¾® NaCl + H2O NaOH + НNO3 ¾® NaNO3 + H2O NaCl + AgNO3 ¾® AgCl + NaNO3 B. Discovery of halogen by destruction of organic matter by combustion Rea cts: chloroform, 1% silver nitrate solution Halogens are detected in the form of halide ions by the formation of flocculent precipitates of silver halides of various colors: silver chloride is a white precipitate that darkens in the light; silver bromide - pale yellow; silver iodide - intense yellow. A strip of filter paper is moistened with chloroform and lit under an inverted large glass. After the paper burns, dewdrops of water appear on the inner walls of the glass. The glass is turned over and a few drops of a 1% solution of silver nitrate are added. The formation of a cloudy or white cheesy precipitate indicates the presence of a halogen in the chloroform under study. CHCl3 + O ¾® CO2 + H2O + HCl НCl + AgNO3 ¾® AgCl + НNO3 Experiment 12. DETECTION OF NITROGEN Rea cts: urea, sodium metal, 5% ferrous sulfate solution, 1% ferric chloride solution, 8% hydrochloric acid solution, ethyl alcohol. Nitrogen is qualitatively detected by the formation of Prussian blue - Fe43 - blue color. The experiment is carried out in a fume hood behind glass or wearing safety glasses, following the instructions below. If sodium metal is handled carelessly, an accident may occur. Several crystals of the test substance, urea, are placed in a dry test tube, and a small piece of metallic sodium, well cleared of the oxidized layer, is also added there. Carefully heat the test tube over the burner flame, holding it in a wooden clamp and making sure that the sodium melts along with the substance; the hole of the test tube is directed Push . After some time, an outbreak may occur. The test tube continues to be heated until a homogeneous alloy is obtained, then it is cooled and a few drops of alcohol are added to remove residual sodium metal, which reacts with alcohol according to the equation: H5ОH + Na C2H5ONа + Н2 1-2 ml of water is poured into the test tube and heated until dissolved, 2-3 drops of a freshly prepared solution of ferrous sulfate, a drop of ferric chloride are added to part of the solution and acidified with hydrochloric acid (to neutralize the alkali formed in the solution). If nitrogen is present in the test substance, a blue precipitate of Prussian blue appears: NCONH2 + Na NaCN+ FeSO4 Na2SO4 + Fe(CN)2(CN)2 + NaCN Na4Fe(CN)6Fe(CN)6 + FeCl3 Fe43 Experiment 13. DETECTION OF SULFUR REACTIVES: sulfanilic acid, sodium metal, lead acetate, 1% sodium nitroprusside solution, 8% hydrochloric acid solution, ethyl alcohol Sulfur is qualitatively detected by the formation of a dark brown precipitate of lead (II) sulfide, as well as a red-violet complex with a solution of sodium nitroprusside. A small amount of a sulfur-containing organic substance, sulfanilic acid, and a small piece of sodium metal are placed in a dry test tube. The destruction of a substance by fusion with metallic sodium is carried out in the same way as in the determination of nitrogen. If the resulting solution darkens, it is filtered to remove coal particles. The solution is divided into three parts. To detect the S2- ion, one part of the solution is acidified with hydrochloric acid - a characteristic smell of hydrogen sulfide is felt: Н2NC6Н4SO3Н + Na Na2SS + HCl H2S + NaCl A solution of lead acetate is added to the second part of the solution, acidified - a black precipitate of PbS or brown turbidity forms: Pb (CH3COO)2 + Na2S PbS ¯ + 2CH3COONa A few drops of freshly prepared sodium nitroprusside solution are added to the third part of the solution. The appearance of a red-violet color is observed due to the formation of a complex salt: Na2S + Na2 Na4 III.1 CLASSIFICATION, ISOMERITY AND NOMENCLATURE OF ORGANIC COMPOUNDS In the mid-9th century, with intensive developments in the field of organic chemistry, the need arose to define a new theory. In 1861, at the International Congress of Naturalists and Doctors in Speyer, A.M. Butlerov proposed new theory structure of organic substances, the provisions of which are as follows: 1.Atoms in organic compounds are bonded to each other in a strict sequence, according to their valency. The sequence of bonding of atoms in a molecule is called chemical structure. 2.The chemical properties of a substance depend not only on which atoms and in what quantity are included in the molecule, but also on the sequence in which they are connected to each other, i.e. on the chemical structure of the molecule. .Atoms in organic compounds have a mutual influence on each other, which determines the reactivity of the molecule. .By studying the reactivity of a substance, one can establish its structure and, conversely, judge its properties by the structure of the substance. One of the classified characteristics of organic compounds is the structure of the carbon skeleton and the nature of functional groups. According to the first criterion, organic substances are divided as follows: ORGANIC COMPOUNDS ACICLIC CYCLIC CARBOCYCLIC HETEROCYCLIC ALICYCLIC AROMATIC Functional groups are atoms or groups of atoms of a non-hydrocarbon nature, which, being substituents in the hydrocarbon chain, determine the chemical properties of molecules. Based on the nature of the functional group, various classes of organic compounds are distinguished, the main ones of which are given in Table 3.1. Table 3.1. Classification of organic compounds by the nature of functional groups. Class nameFunctional groupGeneral formula of the classHalogen derivatives of hydrocarbons-F, -Cl, -Br, -IR-HalAlcohols, phenols-OHR-OHThioalcohols, thiophenols-SHR-SHEthers-ORR-O-RAldehydes-CH=OR-CH=OKetones >C=OR2C=OCarboxylic acids-COOHR-COOHSulfonic acids-SO3HR-SO3HEsters-COORR-COOR ¢ Amides-CONH2R-CONH2Nitriles-C º NR-C º Nnitro compounds-NO2R-NO2Amines-NH2R-NH2 Based on the number and homogeneity of functional groups, organic compounds are divided into monofunctional, polyfunctional and heterofunctional. Monofunctional organic compounds contain one functional group, polyfunctional - several identical ones, heterofunctional - several different groups. The nomenclature of organic compounds evolved throughout the entire period of development of organic chemistry. In the historical aspect, the main nomenclature systems should be highlighted: trivial, rational and international. Trivial names are random, they reflect the methods of obtaining substances, their distinctive properties or the natural source from which the compounds were first isolated, for example, pyragallol is a product of pyrolysis of gallic acid, fluorescein fluoresces. Many trivial names for organic compounds have firmly established themselves and are still generally accepted, especially in the chemistry of natural and heterocyclic compounds. According to rational nomenclature, all substances in a certain homologous series are considered as derivatives of the simplest representative of this series, in particular for alkanes - methane, for alkenes - ethylene, for acetylenes - acetylene, etc. However, due to the increasing complexity of chemical structures, this nomenclature turned out to be unsuitable, so at the XIX Congress of the International Union of Pure and Applied Chemistry in 1957, the rules of modern nomenclature, known as the “IUPAC nomenclature,” were developed. The IUPAC nomenclature provides several options for the names of organic compounds: substitutive and radical-functional. When naming alkanes according to the IUPAC substitutive nomenclature, the following rules are followed: 1.The name is based on the name of the hydrocarbon that corresponds to the longest unbranched chain (main carbon chain). If a hydrocarbon has several chains of the same length, the one with the largest number of branches is taken as the main one. 2.The carbon atoms of the main chain are numbered from the end to which the substituent is closest; if in the alkane molecule the substituents are located at an equal distance from both ends, then the numbering is carried out from the end to which the substituent with the name that comes first in alphabetical order is located closer. If identical substituents are located at equal distances from both ends of the main chain, but there are more branches on one side than on the other, numbering begins from the end with the greater number of substituents. CH3-CH-CH-CH2-C-CH2-CH2-CH32,5-dimethyl-5-ethyl-3-isopropyl octane CH3 CH2-CH3 The diversity of organic compounds is due to the phenomenon of isomerism. Isomers are compounds with the same elemental composition and molecular weight, but differing in structure. The following types of isomerism are distinguished: ISOMERIA STRUCTURAL SPATIAL (structural isomerism) (stereoisomerism) CHAINS OF POSITION OF FUNCTIONAL GROUPS CONFIGURATION CONFORMATION GEOMETRIC OPTICAL For example: Chain isomers CH3-CH2-CH2-CH3 and CH3-CH-CH3 n-butane CH3 2-methylpropane (isobutane) Position isomers CH2=CH-CH2-CH3 and CH3-CH=CH-CH3 butene-1 butene-2 3.isomers by functional group butanal methyl ethyl ketone 4.geometric isomers of butene-2 cis-butene-2 trans-butene-2 5.conformational isomers of propane obscured inhibited 1.Name the main ways to depict organic molecules. Write the structural and abbreviated formulas of the following compounds: a) n-butane, b) cyclopentane, c) propene, d) ethanol, e) acetic acid. 2.Name the main advantages of structural formulas in comparison with molecular (gross) formulas. Write all possible structural formulas of compounds whose gross formula is: a) C4H8, b) C3H8O, c) C3H7C1. .Name the following compounds. a) H3C-C=CH-CH2-CH3 b) H3C-CH-COOH ï ï
c) H3C-CH-CH2-CH2-COOH d) H3C-C-CH2-CH2Br ï ïï
e) CH3-CH2-C = C-CH3 f) H2C=CH-C º C-CH3 H3C CH2-CH3 4.Name the main nomenclature systems of organic compounds and indicate by which of them the names of the following compounds are formed: a) n-heptane, b) tetramethylmethane, c) ethyl alcohol, d) glycerin, e) acetic acid, f) pentanol-2, j) propanoic acid. Write their structural formulas. 5.Write the structural formulas and indicate the primary, secondary, tertiary and quaternary carbon atoms in the following compounds: a) 3-methylpentane, b) 2,2,4,4-tetramethylhexane, c) ethylcyclohexane, d) 2-methyl-2-phenylbutane. .Write the structural formulas of the following compounds: a) 2,2,4-trimethylpentane, b) 2-chloropropene, c) 3-bromohexane, d) 2-methyl-3-chloro-3-ethylhexane, e) 2-methylbutene-2, e) methyl acetylene. .Name the compounds using IUPAC substitutive nomenclature and rational nomenclature: CH2-CH3 CH3 ï ï
a) CH3-CH-CH-CH3 b) CH3-CH2-CH-CH2-CH-CH3 ï ï
CH3 CH2-CH3 H3C-H2C CH3 CH3 ï ï ï
c) CH3-CH-CH-C-CH3 d) CH3-CH2-CH-CH-CH3 ï ï ï
CH3 CH-CH3 H3C-CH-CH3 8.Define the concepts “isomerism”, “structural isomers”, “stereoisomers”, “conformational isomers”, “geometric isomers” and “optical isomers”. 9.Write the structural formulas and name the isomers of the composition C6H14. .Using Newman's projection formulas, depict the eclipsed and inhibited conformations of n-butane resulting from rotation around the C1-C2, C2-C3 bonds. Indicate the anti- and gauche conformations. .Using Newman's projection formulas, give the conformational isomers of: a) 2-chloroethanol, 2) 2-aminoethanol, c) 1,2-dibromoethane, d) ethylene glycol. Indicate the energetically more stable conformers. Name the compounds that correspond to the given Newman formulas: a B C) III.2 CHEMICAL BONDING AND MUTUAL INFLUENCE OF ATOMS IN ORGANIC COMPOUNDS There are four main types of chemical bonds in organic compounds: covalent, ionic, hydrogen, donor-acceptor. A bond formed by sharing electron pairs is called a covalent bond. It is formed between atoms of equal or similar electronegativity and is the main type of chemical bond in organic compounds. A bond formed between atoms with the same electronegativity is called a non-polar covalent, and a bond formed between atoms with a slight difference in electronegativity is called a polar covalent. An ionic bond is formed between atoms that differ significantly in electronegativity. As a result, oppositely charged ions are formed, which are electrostatically attracted to each other. CH3COO- Na+ ionic bond A donor-acceptor bond is a type of covalent bond and differs from the latter only in the method of formation. If a covalent bond is formed by sharing a pair of electrons, one from each atom, then a donor-acceptor bond is formed by sharing two electrons provided by one of the atoms. In this case, the one supplying a pair of electrons for general use is called a donor, and the atom receiving electrons is called an acceptor. For example: Н N: + Н+ Н N Н H donor acceptor H A special case of a donor-acceptor bond is a semipolar bond. It is formed by the interaction of atoms having lone pairs of electrons (donors) with electrically neutral particles that contain a sextet of electrons (acceptors). A hydrogen bond is formed as a result of electrostatic interaction between active hydrogen atoms in a molecule and atoms with a lone electron pair (O, N, F) in the same or another molecule. N ¬H ··· N- -N ¬ H···O<
hydrogen bond The energy of a hydrogen bond (10-40 kJ/mol) is small compared to the energy of a covalent bond (340-360 kJ/mol). There are intramolecular and intermolecular hydrogen bonds. Intramolecular hydrogen bonds occur within a single molecule to form five-, six-, or seven-membered chelate-like structures (1). Intermolecular hydrogen bonds occur between two or more molecules with the formation of dimers (2) or associates (3). The carbon atom is characterized by three types of hybridization involving s- and p-orbitals: sp3-, sp2-, sp-. sp3 hybridization is characteristic of alkanes, sp2 - for alkenes, sp - for alkynes. In organic compounds, two types of electronic displacements are distinguished: the inductive effect and the mesomeric effect. The shift in electron density along a chain of s-bonds is called the inductive effect (I), and along the system of p-bonds - the mesomeric effect (M). The inductive effect always appears when there are atoms with different electronegativity in the molecule, propagates only in one direction and decays after 3-4 s-bonds. It can be positive (+I) and negative (-I). CH3 CH2 CH2 Cl (-I) CH2 =CH CH3 (+I) The mesomeric effect appears only when the substituent is included in the conjugated system of the molecule. There are p,p-conjugation (=-. .) and p,p-conjugation (= - =). CH2=CH Cl: CH2=CH CH= O CH2=CH CH2 Cl (+M) (-M) (M=0) TEST QUESTIONS AND EXERCISES 1.Formulate the basic principles of A.M. Butlerov’s theory of the chemical structure of organic molecules. 2.Indicate the types of chemical bonds in the following compounds: trinitroglycerin ethanol Sodium acetonitrile γ-hydroxybutyrate methyl ammonium iodide vinyl acetylene Give the electronic formulas of carbon, nitrogen and oxygen atoms. Explain why carbon in organic compounds is tetravalent. What types of hybridization are possible for a carbon atom in organic compounds? Draw the atomic orbital patterns in the molecules of ethane, ethylene, and acetylene. How does the electronegativity of a carbon atom change depending on hybridization? Determine the hybridization of the carbon atom in the starting compounds and final reaction products: 6.Inductive effect. Show graphically the manifestation of the inductive effect of substituents in the following organic compounds, indicating the electron-donating and electro-accepting substituents: a) CH3-CH2-C1 b) CH3-CH2-COOH c) CH2=CH-C º CH d) CH3-C(O)H d) CH3-CH=CH2 f) CH3-C º N 7.Coupled systems with open and closed circuits. Determine the types of conjugation and show the distribution of electron density in the molecules of the following compounds: a) CH3-CH=CH2 b) CH2=CH-CH=CH2 c) CH2=CH-C1 d) CH3-CH=CH-COOH e) C6H5OH f) C6H5-C1 8.Mesomeric effect. Combined manifestation of inductive and mesomeric effects of substituents. Indicate the inductive and mesomeric effects in the following compounds: 9.What properties - electron-donating or electron-withdrawing - do functional groups exhibit in the 3-methoxypropanal molecule? 10.Write the trans-isomer of cinnamic acid (C6H5-CH=CH-COOH) and determine the conjugated system, type and sign of the electronic effects of the carboxyl group. .Indicate the type and sign of electronic effects for the following compounds: chloroprene, 4-hydroxybutanoic acid, 2-ethoxybutane, ethoxybenzene (phenetol), methoxybenzene (anisole), aniline, 2-hydroxybenzoic acid, benzaldehyde, benzyl alcohol, chlorobenzene, benzyl chloride, allyl chloride, vinyl chloride , crotonic acid, butanoic acid. Do the same functional groups exhibit the same electronic effects in 2-aminoethanesulfonic acid (taurine) and p-aminobenzenesulfonic (sulfanilic) acid molecules? Give the spatial arrangement of orbitals in the molecule of propylene, propyne and propane. Specify the number of s-, p-, sp3-, sp2-, sp-orbitals III.3 ALKANES. CYCLOALKANES Alkanes or saturated hydrocarbons are hydrocarbons of the aliphatic series, in the molecules of which the carbon atoms are connected to each other only by simple covalent bonds. Their composition is expressed by the general formula СnH2n+2. The ancestor of the homologous series is methane. Each member of this series differs from the next one by a CH2 unit. The ending -ane is characteristic of alkanes. All carbon atoms in alkanes are sp3 hybridized and have a tetrahedral shape. Alkanes with branched carbon chains are called according to the IUPAC substitutive and rational nomenclature. Alkanes are characterized by structural and optical isomerism. The structural isomerism of alkanes is due to the different sequence of bonding of carbon atoms in the molecule (chain isomerism). Starting from the hydrocarbon C7H16, optical isomerism is possible for alkanes. For example, 3-methylhexane CH3-CH2-CH-CH2-CH2-CH3 has an asymmetric carbon atom and exists in the form of two enantiomers (mirror isomers): ï ï
CH3-CH2 CH2-CH2-CH3 CH3-CH2-CH2 CH2-CH3 R-3-methylhexane S-3-methylhexane The main natural sources of alkanes are oil and natural gas. To obtain a mixture of alkanes and other hydrocarbons from oil, it is subjected to fractional distillation. There are also synthetic methods for their preparation: a) catalytic hydrogenation of carbon monoxide (II) (Fischer-Tropsch synthesis), b) catalytic hydrogenation of alkenes and alkynes, c) interaction of haloalkanes with sodium metal (Wurtz reaction), d) fusion of carboxylic acid salts with alkalis. Under normal conditions, alkanes are poorly reactive compounds. They are resistant to acids, alkalis and oxidizing agents. Chemical transformations of alkanes are often accompanied by homolytic cleavage of C-H bonds followed by the replacement of the hydrogen atom with other atoms or groups, i.e. they are characterized by substitution reactions occurring according to the radical mechanism (SR). At high temperatures, homolytic cleavage of C-C bonds can occur. Cycloalkanes are cyclic hydrocarbons in which all the carbon atoms forming the cycle are in an sp3-hybridized state. Cycloalkanes are classified by ring size, number of rings, and how the rings are connected. In accordance with IUPAC rules, the names of monocyclic cycloalkanes are formed from the names of alkanes with the corresponding number of carbon atoms, adding the prefix cyclo-. Cycloalkanes are characterized by structural, geometric and optical isomerism. Cycloalkanes such as cyclopropane and cyclohexane, as well as their homologues, are part of some types of oil, from which they can be isolated in pure form. Along with this, there are a number of synthetic methods for the production of cycloalkanes: a) the interaction of dihaloalkanes with metallic sodium or zinc, b) pyrolysis of calcium salts of dicarboxylic acids, c) cycloaddition reactions. Similar to alkanes, the carbon atoms in cycloalkane molecules are in a state of sp3 hybridization. But if alkane molecules have significant flexibility due to free rotation around carbon-carbon bonds, then cycloalkane molecules, despite possible conformational turns, are to a certain extent rigid formations. Chemically, cycloalkanes behave in many ways like alkanes. However, they are characterized not only by substitution reactions occurring through the radical mechanism (SR) (for ordinary rings - five- and six-membered), but also addition reactions in accordance with Markovnikov’s rule according to the electrophilic mechanism (AE) (for small rings - three- and four-membered). This phenomenon is explained by the spatial structure of cycloalkanes. Alkanes and cycloalkanes are widely used in the chemical industry as raw materials for the production of a wide range of many organic substances, medicine, pharmacy in the manufacture of dosage forms, and in the perfume and cosmetics industry. For example, petroleum jelly (a mixture of liquid and solid alkanes with the number of carbon atoms from 12 to 25) is widely used in pharmacy as a base for the preparation of ointments, cyclopropane is used in medical practice as a means for inhalation anesthesia. TEST QUESTIONS AND EXERCISES CH2-CH3 CH3 ï ï
a) CH3-CH-CH3 b) CH3-CH2-C-CH2-CH-CH3 ï ï
CH3 CH2-CH3 CH3 CH3 CH3 CH2-CH3 ï ï ï ï
c) CH3-CH-CH-C-CH3 d) CH3-CH-CH-CH3 e) CH3-C-CH3 ï ï ï ï
H3C CH-CH3 H3C-CH-CH3 CH3-CH-CH3 SO 2, Cl 2, hv NaOH Br 2,hv Na dil. HNO 3,t,p a) CH 3-CH-COONa 1 2 3 5 ï
CH 3 Cl 2, hv
HBr H 2, cat .
Zn 3
b) 1,3-dibromo-2-methylpropane 1 Cl 2, hv Cl 2
PREFACE
A course in organic chemistry can only be mastered if students personally become familiar with substances and their transformations through experiments and syntheses they conduct.
Experience shows that involving students in performing exercises in organic chemistry in parallel with lecture courses and laboratory practical work should become an integral element of the educational process, and theoretical exercises should be included in the curriculum. For more conscious participation by part-time students in laboratory practical work, a brief theoretical background is given for each work. Therefore, the teacher’s preliminary explanations at the beginning of the work are kept to a minimum, and students must independently understand the conditions for the course of reactions and theoretical issues related to this topic. The same goal of consolidating structural chemical concepts and developing deeper chemical thinking is served by questions and exercises placed at the end of each work.
For more in-depth study a course in organic chemistry and the acquisition of experimental laboratory skills necessary for carrying out scientific research; part II of the workshop includes syntheses of organic substances of the fatty and aromatic series.
Studying common methods laboratory practice is necessary, since they form the basis of future practical and research work of students.
Carrying out experimental work in the laboratory requires compliance with a number of conditions. These conditions make it possible to ensure completion of the work and prevent possible cases accidents and create work safety for both the leader and those around him.
Necessary:
1) strictly comply with all safety rules established for this laboratory;
2) proceed to the experimental part of the work only after preliminary familiarization with the theory of the issue, with the design of instruments, with the necessary (safety measures;
3) carry out the work carefully, carefully, without undue haste, but at the same time quite intensively;
4) do not leave the device in which the reaction with heating or distillation is taking place; Special attention pay attention to techniques for working with flammable and potent substances (ether, gasoline, gasoline, nitric acid, sulfuric acid, etc.);
5) carefully monitor the cleanliness of dishes, equipment and the workplace.
The author hopes that this manual will benefit students of our institute and will help them master the course of organic chemistry, the knowledge of which is so necessary for the subsequent successful study of a number of technical disciplines.
INTRODUCTION
Organic chemistry not so long ago, some hundred years ago, occupied an insignificant place among other disciplines. It took shape as a science in the 19th century; However, man's acquaintance with organic substances and their use for practical purposes began in ancient times.
In the middle of the 18th century. one of the greatest sons of the Russian people, M. V. Lomonosov, established the fundamental law of nature - the law of conservation of matter, laid the foundation for physical chemistry and atomic-molecular science, and also created the world's first scientific chemical laboratory. In 1842, N.N. Zinin gained world fame, whose discovery - the transformation of nitrobenzene and its homologues into aniline and the corresponding amino derivatives of alkyl benzenes - is the cornerstone of the entire edifice of the aniline dye industry.
In the second half of the 19th century. the great Russian scientist D.I. Mendeleev discovered the periodic law, which laid the unshakable foundation of the modern doctrine of chemical elements. The outstanding Russian chemist A.M. Butlerov in 1861 created the theory of the structure of organic compounds, which in our time is the basis of organic chemistry and related her disciplines. However, several years after the creation of the theory of structure, A.M. Butlerov had to speak out in defense of his priority from foreign chemists, who at first did not recognize or even understand his theory, and subsequently tried to attribute the honor of creating the main provisions of this theory to themselves.
By the beginning of the 20th century. achievements of our greatest creators of organic synthesis and catalysis - V.V. Markovnikova, A.M. Zaitsev,
N. D. Zelinsky, A. E. Favorsky, N. Ya. Demyanov, the discoveries of the most prominent Russian physical chemists - N. N. Beketov, D. P. Konovalov, the founder of physical and chemical analysis N. S. Kournikov, a remarkable chemist L. A. Chugaeva - received wide fame and universal recognition. However, the conditions for widespread development chemical research and the creation of chemical schools in pre-revolutionary times was extremely unfavorable.
The chemical industry of pre-revolutionary Russia, due to its insignificant size, did not at all meet the needs of the country and was largely in the hands of foreign capitalists.
In the years Soviet power The entire domestic chemical industry with its numerous and varied production facilities was essentially re-created.
The rapid development of Soviet chemistry, the increase in its role in the national economy and in the rise of culture were reflected in the well-known slogan proclaimed at the 18th Party Congress: “The Third Five-Year Plan is the Five-Year Plan of Chemistry.”
The congress decided: “To transform the chemical industry into one of the leading industries, to fully satisfy the needs of the national economy and defense of the country.”
Soviet organic chemistry developed in close connection with the rise of the coal and oil industries, the use of abundant forest and plant resources, and in accordance with the rapidly developing needs of the national economy, defense and health care. Various branches of basic and fine organic synthesis, the chemistry of motor fuel and the production of high-molecular compounds have received especially great development. During the years of the five-year plans, industrial production was created various types synthetic rubber, motor fuel, plastics, artificial fibers, explosives, alcohols, organic acids and esters, as well as dyes, medicines, vitamins and other fine organic products.
Soviet organic chemistry adopted and continued the glorious traditions of the luminaries of Russian science - N. N. Zinin, A. A. Voskresensky, A. M. Butlerov, V. V. Markovnikov, A. M. Zaitsev, E. E. Vagner and other major representatives of organic chemistry.
If the world-famous discoveries of N. N. Zinin, which laid the foundation for the anilo-dye industry, remained unnoticed and unused in Russia at one time, but were picked up and used by German industrialists, then the synthesis of rubber carried out in 1928 by S. V. Lebedev was the basis the world's first Soviet synthetic rubber industry and served as an impetus for the creation of similar production facilities in Germany and then in the USA.
In addition to the synthetic rubber industry, over the years of the five-year plans, many other branches of the organic chemical industry were created: aniline; chemical-pharmaceutical; plastics and artificial fibers; cellulose; industry of heavy organic synthesis based on cracking of gases, carbon monoxide, acetylene; motor fuel industry (catalytic cracking and other types of petroleum processing).
1 Resolution of the CPSU(b). Ed., 6th, vol. II, p. 732.
One of the areas of Soviet organic chemistry that has received a bright and unique development is the chemistry of hydrocarbons and their transformations. Hydrocarbons have long been of interest to Russian chemists, perhaps because our country is home to the most valuable and largest oil fields. The names of A. M. Butlerov, V. V. Markovnikov, G. G. Gustavson, K. N. Kizhner, N. Ya. Demyanov, N. D. Zelinsky, A. E. Favorsky, are associated with the development of hydrocarbon chemistry. S. V. Lebedev, S. S. Nametkin and many others.
The synthesis of rubber starting from alcohol belongs entirely to the outstanding Soviet researcher S.V. Lebedev. His method formed the basis of a new synthetic rubber industry, which developed rapidly and freed the Soviet Union from the need to import it from abroad.
Indeed, new synthetic rubber factories created in the pre-war years made it possible Soviet Union to avoid difficulties in supplying rubber to the army, navy and aviation in the Second World War.
Soviet chemists achieved great success in the field of one of the most important unsaturated hydrocarbons - acetylene. Academician A. E. Favorsky and the school of chemists he created devoted numerous works to the transformations of this hydrocarbon, based primarily on the ability of acetylene discovered by A. E. Favorsky to react with alcohols , ketones and aldehydes in the presence of sodium hydroxide.
The chemistry of organic compounds of metals and other elements (phosphorus) developed with great success in the Soviet Union. Scientific schools created by A. E. Arbuzov, A. V. Topchiev,
A. N. Nesmeyanov, V. M. Rodionov, found new methods for the synthesis of such compounds, new types of their transformations and promoted their practical use.
The work of Soviet chemists in the field of terpenes: E. E. Wagner and L. A. Chugaev is of greatest theoretical, and partly practical interest. These works mainly owe their origin to the research of S. S. Nametkin and his school, as well as the school of A. E. Arbuzov.
The beginning of a new stage in the development of the domestic chemical industry is associated with the resolution of the Plenum of the CPSU Central Committee of May 7, 1958, based on the report of Comrade N. S. Khrushchev “On accelerating the development of the chemical industry and especially production synthetic materials and products made from them to meet the needs of the population and the needs of the national economy.”
The plan for the accelerated development of the production of synthetic materials and the entire chemical industry of the USSR, in its significance, ranks among such gigantic achievements Communist Party and the Soviet people, like the GOELRO plan, plans for the industrialization of the country and collectivization Agriculture.
In a report at the Plenum of the CPSU Central Committee, Comrade N. S. Khrushchev said: “ Latest discoveries in the field of chemical engineering make it possible to make fuller use of the rich natural resources in the national economy of the country, to develop on an unprecedented scale the production of high-quality goods from synthetic materials, which, together with a steep rise in agriculture, will make it possible in the coming years to sufficiently satisfy the growing needs of the population in clothing, footwear, household and household items."
The measures planned by the 21st Congress of the CPSU for the accelerated development of industry provide for an increase in the production of chemical products. in 1959 - 1965 approximately 3 times, and the production of plastics and synthetic resins should increase by more than 7 times, the production of artificial fibers by 4 times, and the most valuable synthetic fibers by 12-13 times.
It is planned to build and reconstruct more than 270 enterprises in the chemical industry and related industries. It is planned to invest over 100 billion rubles in the development of the chemical industry. The implementation of this grandiose program will be a new major contribution to the solution of the main economic task of the USSR outlined by the 20th Congress of the CPSU: in the shortest possible time to catch up and surpass the most developed capitalist countries in per capita production.
The very rapid introduction of polymer materials into various industries is due to their remarkable properties.
The most important qualities of synthetic high polymers, due to which they are so widespread, are low specific gravity, high mechanical strength, elasticity, chemical resistance, high sealing properties, the ability to absorb and dampen vibrations, adhesive ability and, most importantly, the ability to easily obtain products with a wide range of physical mechanical properties. A wide range of physicochemical and mechanical properties of polymeric materials is largely determined by the nature of atoms and side groups, the size, shape and degree of flexibility of chain molecules. Depending on the need, high-molecular compounds with a wide variety of properties are obtained: from combustible, flammable to completely non-flammable; from water-soluble to practically non-absorbing moisture; from hard, almost steel-like in strength, to elastic, rubber-like and even viscous.
World science has contributed enormously to the creation of new chemical substances - polymers. An honorable role here belongs to Russian and Soviet chemists. The fundamental work in this area was done by A.M. Butlerov. S. V. Lebedev was the first to develop scientific methods for the industrial production of synthetic rubber.
Great achievements in the development of theory and (The polymer industry belong to I. I. Ostromyslensky, B. V. Byzov, I. J. Kondakov, P. P. Shorggin, G. S. Petrov - a pioneer of domestic science and industry plastics, x mass - and many other advice to scientists and engineers. K. A. Andrianov was the first to develop a method for the synthesis of organosilicon polymers - silicones!, which are now widely used. Back in the mid-thirties, A. I. Dintse first published the results of laboratory experiments on polymerization ethylene under high pressure. The first scientific publication on emulsion polymerization belongs to B. A. DogaDkin. Based on his theoretical research, B. A. Domoplosk developed an industrial method of emulsion polymerization using redox compounds. S. N. Ushakov and A. A. Berlin proposed a new method for changing the properties of p-polymers (graft polymerization) and applied it to the production of different types of polymer materials. V. A. Kargin and N. V. Mikhailov proposed new method strengthening of viscose fiber (plasticization with hot water), which is now widely used in industry. A. N. Nesmeyanov, S. S. Medvedev, I. JI made a great contribution to polymer science and technology. Knunyants,
V. V. Korshak, A. A. Koroegnov. The works of Acad. N. N. Semenov on the theory of chain processes, allowing one to approach scientifically based control of chemical reactions.
World production of synthetic polymer materials has already exceeded 7.5 million tons and continues to develop at a rapid pace. In 15 - 20 years, world production of these polymer materials will reach 20 - 35 million g, which will amount to 23 times the volume of modern steel production.
Archaeologists divide the entire history of mankind into the Stone, Bronze and Iron Ages. If the name of the century is determined by the type of material from which the main tools of production are made, 1*0 it is quite possible that the coming century will be called the century of polymers.
Along with homogeneous polymer materials, combined materials are becoming increasingly important. Particularly durable are polymers reinforced with textile fabrics, glass fabric, fiberglass, wood veneer, and polymer fibers. Reinforced plastics are close in strength to duralumin, and some of them are close to steel.
Great technical prospects are opened up by ultra-light plastics - foam and honeycomb plastics. These materials are 10 to 100 times lighter than water and offer unsurpassed heat and sound insulation properties and relatively high strength. By combining foam and honeycomb layers with reinforced plastics, lightweight structural materials are obtained that are increasingly used in aircraft and automobile construction, construction and other industries.
The introduction of fluorine into polymers created new group fluorine-containing plastics, similar in chemical resistance to noble metals.
The exceptionally high growth in plastics production is due, along with technological operational advantages, also to cost-effectiveness.
The specific capital investments required to organize the production of plastics are several times lower than for the production of ferrous and non-ferrous metals.
The raw materials for the production of polymer materials are oil, natural and industrial gases, and cellulose. Their raw material reserves are practically unlimited. With the annual production of polymers in quantities close to the production of steel, only 6-7% of the annual oil production needs to be processed.
The production of polymer materials in advanced technical and economic countries is far ahead of all other industries in terms of the pace of its development. chemical production. Over 10 years (1946 - 1956), the output of the chemical industry in the United States increased by 110%, and the production of high-polymer materials by 220%.
In the Federal Republic of Germany over 4 years (from 1953 to 1956), the average annual growth of the chemical industry was 14 - 15%, and of high-polymer materials - 23 - 27%.
In the Soviet Union, the growth rate of the polymer materials industry was higher: over 6 years (from 1950 to 1956), the output of chemical industry products as a whole increased by approximately 2.5 times, and of polymer materials - by 2.8 times. However, the May Plenum of the CPSU Central Committee in 1958 stated that the North-SSR was seriously lagging behind in terms of production of plastic materials and synthetic fibers. In this regard, the Plenum outlined a program for the accelerated development of the plastic materials industry. The successful implementation of this task is of great importance for the further technical progress of all sectors of the national economy and meeting the needs of the population in fabrics, clothing, footwear and other consumer goods.
JOB #1
OBTAINING ORGANIC SUBSTANCES IN PURE FORM AND DETERMINING MELTING TEMPERATURES
The organic compounds we encounter are in most cases solids, often crystalline, or liquids, and much less often gases.
Reactions in which organic substances participate, in contrast to most reactions of inorganic substances, rarely proceed strictly in one direction and with the formation of only those products that are provided for by the reaction equation. As a rule, they are always accompanied by side reactions, which leads to the formation of a mixture of products.
Isolation of a pure homogeneous substance from a reaction mixture is often associated with significant difficulties. Techniques for the separation and purification of organic substances are very diverse, but can mainly be divided into physical and chemical.
¦Physical techniques are based on the difference physical properties shared connections; chemical - on the difference in their chemical nature. There is no sharp difference between the methods of isolating a substance from a mixture of reaction products and the methods of its subsequent purification. Chemical methods for isolating substances will be discussed in the second part of the laboratory workshop during the synthesis of the corresponding compounds. As for the physical methods for isolating and purifying organic substances, in this manual we are forced to limit ourselves to the use of differences in the solubility of organic substances - recrystallization methods - and differences in their boiling points - the distillation method.
1. Isolation and purification of a substance by crystallization
Separation and purification of a mixture of solids is most often achieved by crystallization - conventional or fractional - from appropriate solvents. The solvents used are water, ethyl alcohol, petroleum ether, acetone, benzene, carbon disulfide, chloroform, acetic acid, etc. They must: a) dissolve the substance well in a hot state and poorly in a cold state; b) not be chemically active in relation to the soluble substance; c) be used in small quantities, since otherwise the dissolved substance is not released or does not crystallize completely.
The essence of the crystallization method is based on the fact that the substance that is more difficult to dissolve in a given solvent or is present in large quantities is crystallized from a hot solution first, since relative to this substance the cooling solution will be supersaturated and crystals of the dissolved substance will begin to separate from it.
From the resulting and filtered solution, upon cooling or upon evaporation of the solvent, the substance is released in a purer form -
Fractional crystallization can be represented by the following diagram, taking A as a more sparingly soluble substance and B as a more easily soluble one: (...)
Place 2 g of crude oxalic acid and 5 cm3 of water in a glass scrubber and heat the contents of the test tube to a boil. The hot solution is filtered through a pleated filter and the precipitation of crystals is observed. Oxalic acid crystallizes in the form of needles. The size of the crystals depends on the cooling rate. The crystals are filtered through a regular funnel and dried between sheets of filter paper.
Solubility of oxalic acid (...)
2. Isolation and purification of substances by distillation
One of the most commonly used methods for the purification and separation of organic substances is distillation. Distillation is a process aimed at separating liquid substances from non-volatile impurities (sometimes solid) or separating volatile substances from each other. The essence of the method of separating mixtures by distillation is that the substance is transferred to the vapor state, and then by cooling the vapor it is returned to the liquid state.
Various distillation methods are used, namely: a) simple, b) fractional or fractionated, c) with steam, d) under reduced pressure.
Each homogeneous liquid has a certain boiling point, depending on pressure. With increasing pressure, the boiling point increases. The dependence of vapor elasticity on temperature has been studied for many pure liquids; it is expressed by a characteristic curve for each liquid.
I If a mixture of liquids having different boiling points is heated to a boil, then the composition of the released vapor will change from the composition of the liquid part; The more volatile part of the mixture first passes into steam. As a result, the temperature of the steam during Distillation continuously increases. As the temperature of steam increases during distillation, the content of liquid in it increases with more high temperature boiling. Therefore, during distillation, the more volatile component is concentrated in the first fraction, and the less volatile component is concentrated in the last fraction or in the residue.
The theory of distillation of mixtures of substances was developed in detail by D. P. Konovalov in 1880 - 1884.
a) Simple distillation
Simple distillation makes it possible to separate only those substances whose boiling points differ significantly (by several tens of degrees) from each other.
Experiment 2. Simple distillation is carried out as follows (Fig. 1). The substance is placed in a round-bottomed flask (Wurtz flask) with an outlet tube soldered to the neck (). When distilling highly volatile substances, flasks with a high-mounted tube are used; In the case of distillation of high-boiling substances, flasks with a low-soldered tube are used. The flask is selected such that the distilled mixture occupies no more than 3U of its volume. Flask
Rice. 1. Simple distillation, connect to the refrigerator so that the end of the outlet tube protrudes from the stopper into the refrigerator by at least 3 - 4 cm. A thermometer (2) is inserted into the neck of the flask using a drilled stopper so that it does not touch the walls of the neck of the flask and the upper part of the mercury bulb of the thermometer was at the same level with the lower edge of the outlet tube. Refrigerators are used to condense substance vapors (3) various sizes. The size of the refrigerator is chosen depending on the distillation speed and boiling point of the distilled liquid; The refrigerator must ensure complete condensation of vapors.
The substance in the distillation flask is heated either directly with a conventional burner under an asbestos mesh or through baths: water, oil or metal, depending on the boiling point of the mixture. (Wood's metal alloy consists of 50 parts by weight of bismuth, 25 parts by weight of lead, 12.5 parts by weight of tin and 12.5 parts by weight of cadmium; melting point 61°). The distillation is carried out at such a speed that it is possible to count the drops of condensate in the receiver. To ensure uniform boiling of mixtures of high-boiling substances, parts of broken fireclay, glass capillaries, pieces of broken porcelain or brick are placed in a distillation flask.
b) Fractional distillation of a mixture of benzene and xylene
Fractional distillation is used to distill a mixture of substances that have closer boiling points. In these cases, simple distillation cannot achieve complete separation of the mixture, but only separate fractions can be isolated: the first, enriched in the more volatile component, and the last, enriched in the high-boiling component.
To achieve good separation of the mixture, repeated distillation of these fractions is used. If, for example, a mixture of equal quantities of benzene (7\.u = 80°) and toluene (Gsh = 110°) is distilled using the method of conventional distillation, then first a mixture containing a lot of benzene and only a little toluene is distilled off. The boiling point of the mixture increases gradually during the distillation process, and the amount of toluene in the distilled mixture increases. Thus, it is not the individual substances that form the mixture that are distilled, but their mixtures; It is very difficult to separate benzene from toluene in this way. Therefore, the separation of such mixtures is carried out by modifying simple distillation; They complement it with a specially designed part - a reflux condenser, which promotes better separation of components.g
In the reflux condenser, due to cooling by outside air, part of the vapors of the distilled mixture condenses, and the condensate will contain a less volatile component, and the vapors will be enriched
Rice. 2. Fractional distillation
more volatile integral part mixtures. When the condensate flowing down comes into contact with the vapors, an interaction will occur between them, leading to additional condensation of the boiling component and evaporation of the volatile component.
The device used for fractional distillation is shown in Fig. 2.
The mixture to be separated is placed in a flask () with a shortened neck, which is connected to a reflux condenser (2) using a stopper. A thermometer is placed in the upper part of the reflux condenser, as in simple distillation. The reflux condenser is connected to the refrigerator using a plug. The vapors of substances formed in the flask during heating must pass through a reflux condenser before passing into the refrigerator. Fractional distillation, thanks to the introduction of a reflux condenser, is a combination of two independently occurring processes: a) repeated partial evaporation of the liquid (rectification) and b) repeated or partial condensation (refluxation).
In fractional distillation, the distillate is collected by dividing it into a number of fractions depending on the temperature range of this mixture. The resulting fractions, each separately, are again subjected to distillation, usually from smaller flasks, and the low-boiling fraction is distilled first. Having distilled the distillate from it to a certain temperature, the next fraction is added to the residue, distilling it in exactly the same way, etc.
Experiment 3. Assemble the device shown in Fig. 2. Only if the device is in full working order can you begin the experiment. Correcting the device during the experiment is difficult and leads to the big one- loss of time and reagents. Before distillation begins, eight dry flasks are also prepared.
A. Place in a round distillation flask 80 cm3 of a mixture consisting of equal amounts of benzene (Bp - 80.5°) and xylene (7 cap = 140°) and a small (pea-sized) piece of pumice or brick, after which - carefully connect the device. The distillation flask containing the mixture is heated in the usual manner. The distillate is divided into four fractions. Substitute a flask () as a receiver and begin to carefully heat the flask; monitor the uniformity of boiling, the readings of the thermometer and the flow of distillate into the receiver. The temperature is noted and recorded when the first drop of distillate falls into the receiver. The distillation is not done quickly, but in such a way that the drops coming from the refrigerator to the receiver can be counted. Changing receivers (cones), collect four fractions in the following temperature ranges: I - up to 90; II - from 90 to 110°; III - from 110 to 125° and IV - from 125 to 140°. When the temperature of the vapor reaches 125°, stop distillation, allow the flask to cool slightly and pour the remaining contents into the fourth receiver-flask (IV - from 125 to 140°). In terms of volume, fraction I is somewhat smaller than the others.
B. Each of the resulting fractions is subjected to a new distillation. During the second distillation, to isolate purer components, 16 times
break the outer fractions (I and IV) into narrower ones and collect the distillate. During the second distillation, fraction I (up to 90°) is placed in a round-bottomed flask and distilled, collecting in a receiver (5) liquid boiling at 90°; then the heating is stopped, the flask is allowed to cool and fraction II from the first distillation is added to the residue. After this, heating is continued and the distillate up to 90° is collected in a cone (1), and the fraction 90 - 110° is collected in a second cone. Heating is stopped when the thermometer shows 110°. After cooling the flask, fraction III is added to the residue and distilled again, collecting new portions of the distillate in the appropriate temperature ranges. When the temperature reaches 125°, the distillation is stopped, the flask is allowed to cool, and fraction IV is added to the residue. Continuing the heating, the part boiling up to 125° is collected in the third receiver, and the shoulder strap, which passes in the range of 125 - 140°, is collected in the fourth receiver.
Thus, after the second distillation, four fractions are obtained again, with the difference that here fractions I and IV are greatly increased due to the decrease in fractions II and III. Using a beaker, the volume of each fraction is determined. The yield of products is calculated as a percentage of the amount of ohms taken for distillation. Having written down the obtained data on the weight and composition of each fraction in a workbook, establish how these indicators change during the first and second distillation.
c) Distillation with water gift
This distillation method has great importance for the isolation and purification of organic substances. The method of distilling organic substances with water steam allows you to distill without decomposition such substances that decompose at boiling point or; high points boiling; on the other hand, this method is used to separate solid and liquid bodies.
If the substances are insoluble in water, then the vapor pressure of the mixture is the sum of the vapor pressures of each of the components that make up the mixture.
Rgateov. When, due to heating, the total pressure becomes equal to atmospheric pressure, the mixture will boil, and its boiling point is below the boiling point of water and soluble substances.
In steam distillation, heating is done by the yir itself. The relative amount of substance distilled off with the water Tsar can be found as follows. Let's say there is a mixture of benzene and water. Benzene boils at 80.5°, water - at 100°. When passing water vapor through this mixture, when reaching atmospheric pressure, i.e. 760 mm Hg. Art., the mixture will boil and benzene and water will be distilled off. The temperature of the boiling mixture is 69.2°. The partial vapor pressure of benzene at this temperature is 535 mm, and that of water is 225 mm.
If the volume of vapor of the mixture at 760 mm pressure is taken as 100, then
The volume of benzene vapor will be = 70.4%, and the volume of water in vapor
100 - 70,4 = 29,6%,-
According to Avogadro’s law, the volumes of gases are proportional to their molecular weights, and since the molecular weight of benzene (C6H6) is 7 and water (H20) is 18, then the weight of benzene will be 70.4X78 = 5,491.2, weight in dy - 29.6x18 = 532.9. How do we know that one part of the water came! contains 10.3 parts of benzene.
For distillation with water steam, install a device (Fig. 3) consisting of a steam generator - a steamer, equipped with a safety tube lowered almost to the bottom, a distillation flask, a refrigerator and a receiver. The pipe through which the steam enters the flask should reach almost to the very bottom of the flask . The flask is positioned somewhat obliquely to reduce the possible transfer of non-removable liquid into the receiver. The flask is filled with liquid no more than one third. The steamer is heated with a strong burner at the same time the flask is carefully heated. The flask is heated in order to avoid a significant increase in the volume of liquid due to condensation of water vapor.
Rice. 3. Steam distillation.
Experiment 4. Carry out a membrane of resin or turpentine, or yoke: pine, or essential oil from some ethereal plants! with water vapor according to the method developed above and isolate the substance from the indicated mixtures in its pure form. (One installation per* group).
3. Determination of the melting point of naphthalene - C10H8
Melting point is a very important physical constant for recognizing organic compounds, since every chemically pure substance has a certain melting point.
Melting point is the temperature at which a substance changes from a solid to a liquid state. Determination of the melting point (Is it done in special, simple devices? (Fig. 4). A thoroughly crushed test substance is placed in glass capillaries, one end of which is melted.
The capillary is filled as follows: its open end is immersed in the substance, then “...the substance is compacted with a glass rod. Usually the capillary is filled to a height of more than 0.5 cm, the capillary itself is taken with a length of 30 - 40 mm and a diameter of 1 - 2 mm. The capillary with ®res is fixed on the thermometer with a rubber ring; the column of the substance should be at the level of the mercury ball The thermometer with a capillary is immersed in a glass with sulfuric acid or azelent oil. Since hot sulfur canine can cause severe burns, when working with it you must be careful (wear safety glasses). The rubber ring should not be in acid.Heating is carried out initially with a large flame, but as the temperature approaches the melting point, it is heated in such a way that the temperature does not rise by more than 1° per minute.
The beginning of melting is considered to be the moment after the
the beginning of the substance, the end - the moment of transformation of belief into a transparent liquid. If the substance is pure, then it melts in the range of 0.5 - 1.0°.
The melting point of naphthalene is 80°.
Questions
1. Discuss the methods for isolating organic substances by crystallization, distillation, and sublimation.
2. In what cases is fractional distillation used? The theory of the th process.
3. Why do additives affect the melting point of a substance?
4. Method for determining the boiling point of a substance.
5. Methods for determining the molecular weights of organic substances.
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MINISTRY OF HIGHER AND SECONDARY SPECIAL EDUCATION OF THE REPUBLIC OF UZBEKISTAN
TASHKENTINSTITUTETEXTILEANDLIGHT INDUSTRY
Department"Chemistry"
UDC547(072).002(076.5)
Educational and methodological manual for performing laboratory work for bachelors TITLP directions:
5522300 - Chemical technology of textile, light and paper industries
ORGANICCHEMISTRY
I.I.Gharibyan ,
A.R. Tulaganov
Tashkent- 20 10
Reviewers
Approved at a meeting of the Scientific and Methodological Council of TITLP from " _ 28 _" __May_ _ 2010, protocol no. _ 5 _
Reproduced at the TITLP printing house in the amount of " _ 25 _" copy
Introduction
The most important condition for the country's development is the improvement of the personnel training system based on economics, science, culture, engineering and technology. The national personnel training program is aimed at radical modernization of the structure and content of the lifelong education system.
State policy in the field of personnel training provides for the formation of a well-rounded personality through a system of continuous education. A special place in the system of lifelong education is occupied by higher education, which, on the basis of general secondary, secondary special, vocational education, is an independent type of lifelong education and is carried out in accordance with the law of the Republic of Uzbekistan “On Education” and the “National Program for Personnel Training”.
One of the defining tasks higher education in accordance with the National Program for Personnel Training is to ensure effective education and training of qualified personnel based on modern educational programs.
Among the disciplines that make up the basic training of chemists in the textile, light and paper industries, organic chemistry occupies an important place.
Organic chemistry - This branch of chemical science that studies carbon compounds their structure, properties, methods of production and practical use.
Compounds that contain carbon are called organic. In addition to carbon, they almost always contain hydrogen, quite often - oxygen, nitrogen and halogens, less often - phosphorus, sulfur and other elements. However, carbon itself and some of its simplest compounds, such as carbon monoxide (II), carbon monoxide (IV), carbonic acid, carbonates, carbides, etc., by the nature of their properties, belong to inorganic compounds. Therefore, another definition is often used: organic compounds are hydrocarbons (compounds of carbon with hydrogen) and their derivatives.
Carbon stands out among all elements in that its atoms can bond with each other in long chains or cycles. It is this property that allows carbon to form millions of compounds, the study of which is devoted to an entire field - organic chemistry.
The role of chemistry in human practical activity and in the development of technology is great. Deep knowledge of chemistry is necessary for specialists: along with physics and mathematics, it forms the basis for the professional training of highly qualified specialists.
Ruleswork in the laboratory of organic chemistry andpreventive actionagainstaccidents
When conducting laboratory work in organic chemistry, you have to deal with flammable, flammable liquids and gases, strong acids and alkalis, and toxic substances. Therefore, the following instructions must be observed:
Before classes, the student needs to become familiar with the progress of the experiments and clearly understand the goals and objectives of the work. You can start performing experiments only after the student has submitted a preliminary report (title, short description course of experience, reaction)
Keep the workplace clean and tidy.
It is prohibited to conduct experiments in dirty containers, as well as to use substances from bottles without labels for experiments.
Work with toxic and strong-smelling substances, with concentrated solutions of acids and alkalis should be carried out in a fume hood
Do not pour out excess reagent or pour it back into the bottle from which it was taken.
If there are no instructions on the dosage of reagents for a given experiment, then they should be taken in the smallest possible quantities. You should not leave burning alcohol lamps unnecessarily.
When working with acids, you must firmly remember the rules for mixing strong sulfuric acid with water - carefully pour the acid into the water in small portions while stirring, and not vice versa.
Do not smell the released gases by leaning close to the bottle. If you need to determine the smell of a gas or liquid, carefully inhale the air, slightly directing the stream of air from the opening of the vessel towards you.
You should never blow on a burning alcohol lamp. Simmer it, covering it with a cap.
Do not work with flammable liquids near heating devices. It is prohibited to heat volatile flammable liquids and substances (ethers, alcohols, acetone) over an open flame. To do this you need to use a water bath.
When heating and boiling a test tube with liquid, the opening of the test tube should be directed away from both the person working and those around him, in order to avoid the release of substances from the test tube.
It is forbidden to taste the reagents.
In case of a burn, apply cotton wool moistened with a 5-10% solution of potassium permanganate or moistened with burn liquid (from the first aid kit) to the burned area.
In case of glass cuts, remove the fragments from the wound, disinfect with a solution of potassium permanganate KMnO4 or alcohol, lubricate the edges of the wound with iodine tincture, put sterilized gauze and absorbent cotton on the wound and tie it tightly with a bandage. After providing first aid, refer the victim to a doctor
If acids or alkalis come into contact with skin or clothing, you must first wash the affected area with plenty of water, then, in case of acid damage, rinse with a 3% sodium bicarbonate solution, and in case of alkali contact, rinse with a 1-2% acetic acid solution. After that, again with water. The alkali is washed off with water until the area of skin on which it comes in contact is no longer slippery. Clothing that came into contact with reagents must be removed.
If you are burned by a hot liquid or a hot object, rinse the burned area with cold running water for 5-10 minutes. You should then be immediately transported to the nearest medical facility.
If acid splashes into the eye, it is washed generously with water so that it flows from the nose to the temple, and then with a 3% bicarbonate solution; if alkali gets in, wash first with water, then with a saturated solution of boric acid.
If poison gets inside, it is necessary to induce vomiting by taking a warm solution table salt(3-4 teaspoons per glass of water). Move the victim to fresh air.
Llaboratory work1
Eelementalanalysisorganic compoundseny
The composition of organic compounds includes: carbon, hydrogen, oxygen, and relatively less often - nitrogen, sulfur, halogens, phosphorus and other elements.
Organic compounds in most cases are not electrolytes and do not give characteristic reactions to the elements they contain. In order to carry out a qualitative analysis of organic matter, it is necessary to first destroy organic molecules by completely burning or oxidizing them. In this case, simpler substances are formed, such as CO2, H2O, which are easily discovered by conventional analytical methods.
Experience1. Determination of carbon andhydrogenA.
The presence of carbon in organic compounds can in most cases be detected by the charring of the substance when it is carefully calcined.
The most accurate method for the discovery of carbon and, at the same time, hydrogen, is the combustion of organic matter mixed with fine powder of copper (II) oxide. Carbon forms carbon dioxide with oxygen in copper oxide, and hydrogen forms water. Copper oxide is reduced to copper metal.
Description of the experience. Fill a dry test tube with a gas outlet tube one-third full with a mixture of starch (well-ground sugar can be used) with powdered copper (II) oxide, taken in excess (Fig. 1). Place a few anhydrous crystals near the opening of the test tube. copper sulfate. The test tube is fixed in a stand in a horizontal position, and the end of the gas outlet tube is inserted to the bottom into another test tube containing 2-3 ml of lime (or barite) water.
The reaction mixture is heated first carefully, then more intensely for 3-5 minutes. After completing the experiment, first remove the end of the gas outlet tube from the test tube and stop heating. Note the changes in the crystals of copper sulfate and barite water. The formation of water droplets on the walls of the test tube and gas outlet tube, as well as the blueing of copper sulfate (formation of CuSO4 * 5H2O) will indicate the presence of hydrogen in the test substance, and the turbidity of lime or barite water will indicate the presence of carbon (formation of a precipitate of barium carbonate BaCO3 or calcium carbonate CaCO3) . Reaction equations:
(C6H10O5)n + 12CuO 6СО2 + 5Н2О + 12Сu
Сa(OH)2 + CO2 СaCO3v +H2О
CuSO4 + 5 H2O CuSO4 * 5H2O
Rice. 1 Determination of carbon and hydrogen in a mixture of starch and copper (II) oxide:
1 - test tube
2 - gas outlet pipe
3 - test tube with lime water
Experience2. Determination of nitrogen and sulfur.
Nitrogen in organic compounds can be detected in various ways. The most common method is the Prussian blue reaction.
To do this, the organic substance is calcined with metallic potassium or sodium. Complete decomposition of organic matter occurs. Carbon, nitrogen and potassium (or sodium) form potassium cyanide (or sodium cyanide). The action of a small amount of iron sulfate converts cyanide salt into iron sulphate. The latter gives a characteristic reaction of the formation of Prussian blue with ferric chloride:
2NaCN + FeSO4 = Fe(CN)2 + K2SO4
Fe(CN)2 + 4NaCN = Na4
3Na4 + 4FeCl3 = Fe43 + 12NaCl
Sulfur can be opened simultaneously with nitrogen. When an organic substance containing sulfur is calcined with sodium metal, sodium sulfide is formed:
The experiment is carried out in a fume hood behind glass or wearing safety glasses, following the instructions below., since careless handling of sodium metal may result in an accident.
Description of the experience. The experiment is carried out in a fume hood behind glass. Several crystals or a drop of the test substance are placed in a dry test tube. A small piece of metallic sodium, well cleaned from the outer layer, is thrown in there. Carefully heat the test tube over a burner flame, holding it in a wooden clamp. After some time, a flash occurs. The test tube is heated for some time until red hot, and then the hot end of the test tube is immersed in a porcelain cup with 3-4 ml of distilled water (Caution! There may be a slight explosion from incompletely reacted metallic sodium!). In this case, the test tube cracks and the contents dissolve in water. The solution is filtered from pieces of coal and glass. A crystal of ferrous sulfate or 2-3 drops of a freshly prepared solution is added to part of the filtrate, boiling for one minute, then a drop of ferric chloride is added and acidified with hydrochloric acid. If nitrogen is present in the test substance, a blue precipitate of Prussian blue appears.
To detect sulfur ions, part of the filtrate is acidified with hydrochloric acid. The characteristic smell of hydrogen sulfide will indicate the presence of sulfur. Lead acetate is poured into the test tube with the remaining alkaline filtrate. In the presence of sulfur, a black precipitate of lead (II) sulfide PbS is formed, or in the case of a small amount of sulfur, the solution turns brown.
Experience3 . Qualitative reactionfor halogens.
TryBelshtein.
To discover halogens, the flame coloring reaction proposed by the chemist F.F. Belshtein is often used. When organic matter is heated in the presence of copper oxide, as seen above, the organic matter burns. Carbon and hydrogen form carbon dioxide and water. Halides form salts with copper. These salts are easily volatile when heated and the vapors color the flame beautifully. green color.
Description of the experience. Copper wire with a diameter of 1-2 mm with a loop at the end is calcined in the colorless part of the burner flame until the color of the flame disappears. In this case, the copper is covered with a black coating of copper (II) oxide CuO. After the wire has cooled, the loop is immersed in a reagent containing a halogen, for example, chloroform, or several grains of the test substance are collected and introduced into the burner flame. In the presence of a halogen, the flame turns a beautiful green color due to the formation of volatile copper halides. To clean, the wire is moistened with hydrochloric acid and calcined again. You should do a control experiment by immersing the wire in a liquid that is known to be halogen-free (distilled water, alcohol). Reaction equation:
2CHCI3 + 5CuO CuCI2 + 4CuCI + 2CO2 + H2O
Hydrocarbons
Hydrocarbons - This is aboutorganic compounds consisting of carbon and hydrogen. Hydrocarbons are classified according to the following structural characteristics that determine the properties of these compounds:
1) structure of the carbon chain (carbon skeleton);
2) the presence in the chain of multiple bonds C=C and C?C (degree
saturation).
1. Depending on the structure of the carbon chain, hydrocarbons are divided into two groups:
*acyclic ( or aliphatic, or fatty hydrocarbons;
*cyclic, characterized by the content of rings or cycles of carbon atoms in the molecule.
Carbon atoms can be connected to each other in chains of different structures:
and different lengths: from two carbon atoms ( ethane CH3-CH3, ethylene CH2=CH2, acetylene CH?CH) to hundreds of thousands ( polyethylene, polypropylene, polystyrene and other high molecular weight compounds).
An open (unclosed) chain of aliphatic hydrocarbons can be unbranched or branched. Hydrocarbons with a straight carbon chain are called normal ( n-) hydrocarbons. Among the cyclic hydrocarbons there are:
*alicyclic(or aliphatic cyclic);
*aromatic (arenas).
In this case, the structure of the cycle serves as a classification feature. Aromatic hydrocarbons include compounds containing one or more benzene rings.
2 . According to the degree of saturation they are distinguished:
*rich(marginal) hydrocarbons ( alkanes And cycloalkanes), in which there are only single bonds between carbon atoms and no multiple bonds;
*unsaturated(unsaturated), containing, along with single bonds, double and/or triple bonds ( alkenes, alkadienes, alkynes, cycloalkenes, cycloalkynes).
Llaboratory work2
Subject : « Saturated hydrocarbons»
Alkaneami - are called aliphatic (alicyclic) limiting hydrocarbons(or paraffins), in the molecules of which the carbon atoms are interconnected by simple (single) bonds in an unbrokenbranched and branched chains.
General formula of saturated hydrocarbons CnH2n+2, where n is the number of carbon atoms. The simplest representatives of alkanes:
When a hydrogen atom is removed from an alkane molecule, single-valent particles are formed called hydrocarbon radicals (abbreviated as R). The names of monovalent radicals are derived from the names of the corresponding hydrocarbons with the ending replaced - en on -il. The general name for monovalent alkane radicals is alkyls. They are expressed by the general formula СnН2n+1.
The formulas and names of the first ten members of the homologous series of alkanes and their normal radicals (alkyl) are given in Table 1
Table 1
|
Monovalent |
||||
To understand the properties of a molecule, it is necessary to consider all the atoms adjacent to each carbon atom. A carbon atom bonded to one carbon atom is called primary , an atom bonded to two carbon atoms, - secondary , with three - tertiary , and with four - quaternary . Primary, secondary, tertiary and quaternary carbon atoms can also be distinguished by the degree of saturation of the carbon atoms with hydrogen atoms.
Example of title construction:
|
Goal of the work: |
Get acquainted with the laboratory method for obtaining the first representative of the homologous series of saturated hydrocarbons and study its chemical properties. |
|
|
Equipment and reagents: |
A gas outlet tube with a stopper, a set of test tubes in a stand, an alcohol lamp, anhydrous sodium acetate CH3COONa, soda lime (a mixture of calcium oxide CaO powders with sodium hydroxide NaOH (3:1), a saturated solution of bromine water Br2, 1% solution of potassium permanganate KMnO4 |
Experience1. Receiptand properties of methane
Methane can be obtained in laboratory conditions by fusing dry sodium acetate and caustic alkali.
Description of the experience. In a mortar, thoroughly grind dehydrated sodium acetate with soda lime (sodium lime consists of a mixture of caustic soda and calcium oxide), mass ratio 1:2. The mixture is placed in a dry test tube (layer height 6-8 mm), closed with a gas outlet tube and secured in a stand.
Separately, 2-3 ml of potassium permanganate solution is poured into one test tube and acidified with 1-2 drops of concentrated sulfuric acid, and 2 ml of bromine water into another test tube.
The mixture in the test tube is heated in the flame of an alcohol lamp and the end of the gas outlet tube is alternately introduced into solutions of potassium permanganate and bromine water. The gas is passed through for 20h30s. After this, the gas outlet tube is turned upside down and the gas is ignited at the end of the gas outlet tube. The color of these solutions does not change, therefore, methane does not react with the taken substances.
Without stopping the heating, the evolved gas is collected. To do this, fill an empty test tube with water and tip it into a cup of water. Place the end of the gas outlet tube under the test tube and fill it with gas. Without removing the test tube from the water, close it with your finger and then bring it to the burner flame. Lit gas burns with a bluish flame. Equations of the occurring reactions:
Llaboratory work3
Subject : “Unsaturated hydrocarbons. Alkenes"
Alkenes (olefins, or ethylene) are called unsaturated hydrocarbons containing one double bond in the molecule and having the general formulaCnH2n.
A double bond consists of one y-bond and one p-bond, which is less strong and therefore easily breaks during chemical reactions.
Carbon atoms in the sp2-hybridized state participate in the formation of such a bond. Each of them has three 2sp2-hybrid orbitals directed to each other at an angle of 120°, and one non-hybridized 2p-orbital located at an angle of 90° to the plane of the hybrid atomic orbitals AO.
Experience1. ReceiptAndproperties of ethylene.
Ethylene can be obtained from ethyl alcohol by removing water:
CH2 - CH2 CH2 = CH2 + H2O
This reaction occurs when alcohol reacts with sulfuric acid in two phases:
1) the formation of ethyl sulfuric acid when mixing alcohol with acid:
C2H5OH + H2SO4 CH3 - CH2 - O - SO3H + H2O
2) elimination of sulfuric acid when the mixture is heated to 1700C:
CH3 - CH2 - O -SO3H H2SO4 + CH2 = CH2
Ethylene, as an unsaturated hydrocarbon, easily enters into an addition reaction, for example, with bromine:
CH2 CH2 + Br2 CH2 - CH2
1,2-dibromoethane
Bromine becomes colorless upon addition, so this reaction is used as qualitative reaction to a double bond. Ethylene oxidation also occurs very easily.
During careful oxidation in an aqueous solution, oxygen and a water molecule are added to form a dihydric alcohol - glycol:
3CH2 = CH2 + 2KMnO4 + 4H2O > 3CH2 - CH2 + 2MnO2v + 2KOH
ethene (c) | |
ethylene (p) OH OH
ethanediol-1,2 (c)
ethylene glycol (r)
The oxidizing agent is usually a weak solution of potassium permanganate. This reaction is called Wagner reactions. During this reaction, potassium permanganate is reduced to manganese (IV) oxide and the solution turns brown. This reaction can also serve as a qualitative reaction to unsaturated hydrocarbons.
Rice. 2 Device for producing ethylene:
1 - burner, 2 - test tube with mixture, 3 - stopper, 4 - tripod, 5 - gas outlet tube, 6 - test tube with bromine water (or potassium permanganate)
Description of the experience. About 5 ml of a mixture consisting of one part ethyl alcohol and three parts concentrated sulfuric acid is poured into a test tube with a gas outlet tube. The mixture is carefully heated (Fig. 2).
Attention! The mixture is dangerous! Place a piece of pumice or dry sand there (for uniform boiling when heating). Pass the released gas through solutions of potassium permanganate and bromine water. Bromine water becomes discolored and potassium permanganate is reduced. The collected gas is set on fire.
Reaction equation:
CH2 CH2 + 3O2 2CO2 + 2H2O
Llaboratory work4
Subject : “Unsaturated hydrocarbons. Alkynes"
Alkynes (or acetylene hydrocarbons) are called unsaturated (unsaturated) aliphatic hydrocarbons, whose molecules, in addition to single bonds, contain one triple bond between carbon atoms.
These hydrocarbons are even more unsaturated compounds than their corresponding alkenes (with the same number of carbon atoms). This can be seen by comparing the number of hydrogen atoms in a row:
ethane ethylene acetylene (ethene) (ethine)
When a triple bond is formed, two electrons from the outer layer participate ( s- And p-), forming two hybrid sp-orbitals. The resulting hybrid orbitals overlap with each other and the orbitals of the hydrogen atom, forming triple bond , consisting of one at- and two
R- connections (bond angle 1800). Therefore, they talk about the linear structure of acetylene hydrocarbons.
Experience1 . ReceiptAndpropertiesAacetylene.
Acetylene is obtained in a test tube with a gas outlet tube by applying water to a piece of calcium carbide (Fig. 3).
The reaction proceeds according to the following equation:
C? C + 2H2O HC? CH + Ca(OH)2
Calcium carbide usually contains impurities of phosphorous compounds, which produce poisonous hydrogen phosphorous when exposed to water, so the reaction to produce acetylene must be carried out in a fume hood.
Rice. 3 Device for producing acetylene:
1- test tube - reactor
2- gas outlet pipe
The resulting acetylene is passed through previously prepared solutions: a solution of potassium permanganate acidified with sulfuric acid, bromine water, and an ammonia solution of copper (I) chloride.
Acetylene adds bromine and is easily oxidized by potassium permanganate. The reaction of bromine addition occurs in two stages:
HC CH + Br2 CHBr = CHBr CHBr2 - CHBr2
ethyn 1,2-dibromoethane 1,1,2,2-tetrabromoethane
The oxidation reaction of acetylene is very complex with the splitting of the molecule. When interacting with a solution of potassium permanganate KMnO4, the raspberry solution becomes discolored. This is another qualitative reaction to the presence of a p-bond in an organic compound.
a) partial oxidation:
3HC? CH + 4KMnO4 + 2H2O > 3 + 4MnO2 + 4KOH
glyoxal
(dialdehyde)
b) complete oxidation
HC? CH + [O] + H2O > HOOC - COOH
acetylene oxalic acid
Just as in previous experiments, the combustion of acetylene in air is studied. Description of the experience. About 1 ml of water is poured into a test tube and a piece of calcium carbide is thrown in. Quickly close the hole with a plug with a gas outlet tube. The reaction proceeds violently and quickly. To slow down the reaction, you can add one drop of diluted sulfuric acid to 3-4 drops of added water. The released gas is passed through previously prepared solutions of potassium permanganate and bromine water. Then collect the gas and set it on fire. Hold a piece of glass high above the flame of burning acetylene. Acetylene burns with the formation of soot (with a lack of air flow) or with a glowing flame (a sign of unsaturation of the compound). Acetylene combustion reaction:
2HC CH + 5O2 4СО2 +2Н2О
HALOID DERIVATIVESEEALIPHATIC HYDROCARBONS (HALOIDALKYLS)
Halogen derivatives of aliphatic hydrocarbons can be considered as hydrocarbon derivatives in which one or more hydrogen atoms are replaced by halogen atoms. Depending on the replacement of one, two, three, etc. atoms into halogens, a distinction is made between monohalogen derivatives and polyhalogen derivatives.
The name of the simplest halide derivatives is usually compiled by analogy with the name of inorganic salts of hydrohalic acids with the designation of the radicals included in their composition. For example, CH3Cl - methyl chloride, etc.
A halide can replace hydrogen at various carbon atoms in the chain. If the halogen is at the carbon bonded to one carbon atom, the halogen derivative is called primary; for example, the compound CH3-CH2-Cl is called primary ethyl chloride. If a halogen is present at a carbon bonded to two carbon atoms, the halogen derivative is called secondary, for example, the compound:
called secondary butyl chloride (2-chlorobutane). And finally, if a halogen is present at a carbon bonded to three carbon atoms, the halogen derivative is called tertiary, for example, the compound:
called tertiary isobutyl chloride (2-methyl 2-chloropropane). All three compounds are isomeric. From these examples it is clear that for halogen derivatives there is both chain isomerism and isomerism of the halogen position. Unlike saturated hydrocarbons, their halogen derivatives are reactive compounds due to the presence of a polar bond between the carbon atoms and the halogen. They can easily exchange a halogen atom for other atoms or groups of atoms, such as - OH, -CN, -NH2, etc.
Llaboratory work5
Synthesis of ethyl bromide
Ethyl bromide can be obtained by one of the general methods for preparing halogen derivatives by the action of hydrohalic acids on alcohols:
C2H5OH + HBr > C2H5Br + H2O
Practically, instead of hydrogen bromide, potassium bromide and sulfuric acid are used. Hydrogen bromide formed as a result of the interaction of these substances reacts with alcohol. The reaction is reversible. To direct it towards the formation of ethyl bromide, an excess of sulfuric acid is taken, which binds the water formed during the reaction.
Some of the alcohol reacts with sulfuric acid to form ethyl sulfuric acid, which then reacts with hydrogen bromide to also form ethyl bromide. The reaction proceeds according to the following equation:
CH3CH2OH + HO- SO3H > CH3CH2 OSO3H + H2O
CH3CH2OSO3H + HBr > CH3CH2Br + H2SO4
Description experience. Pour 5 ml of ethyl alcohol into a 100 ml flask through a dropping funnel and then pour 5 ml of concentrated sulfuric acid in small portions. Since heating occurs during this process, the flask with the mixture is cooled with water, after which 3.5 ml of water is poured into it drop by drop and 5 g of potassium bromide is added. Then the flask is closed with a cork stopper and attached to a refrigerator connected to the allonge. The end of the allonge is lowered into a flask with water so that it is immersed in water by about 1-2 mm. Before the reaction begins, several pieces of ice are thrown into the receiver to better cool the easily evaporating ethyl bromide.
The reaction mixture is carefully heated on an asbestos grid to a boil, without allowing the liquid to foam too much, otherwise it may be transferred to the receiver. The reaction begins quite quickly, which can be detected by the fall of heavy oily drops of ethyl bromide to the bottom of the flask. When the drops of ethyl bromide almost stop falling, heating is stopped.
The resulting ethyl bromide is separated from the aqueous layer. To do this, transfer the entire mixture into a separatory funnel and, carefully opening the tap, pour the lower oily layer into a prepared clean test tube and immediately close it with a stopper.
Ethyl bromide is a heavy, colorless liquid with a sweetish odor, density 1.486 and boiling point 38.40C. Write the reaction equation. Perform a Belstein test for the presence of halogen. Give the resulting drug to the teacher.
Llaboratory work6
Subject : "Aromatic hydrocarbons"
Arenas (or aromatic hydrocarbons) - This connections, whose molecules contain stable cyclic groups of atoms (benzene nuclei) with a special character of chemical bonds.
The simplest representatives:
single-core arenas:
multi-core arenas:
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Naphthalene Anthracene
Benzene is a colorless, highly mobile liquid with a boiling point of 80.10C, which solidifies when cooled into colorless crystals with a melting point of 5.530C, and has a peculiar odor. It ignites easily and burns with a smoky flame. Judging by the summary formula, it can be assumed that benzene is a highly unsaturated compound, similar, for example, to acetylene.
However, the chemical properties of benzene do not support this assumption. Thus, under normal conditions, benzene does not give reactions characteristic of unsaturated hydrocarbons: it does not enter into addition reactions, and does not discolor the solution of potassium permanganate KMnO4.
In a benzene molecule, all carbon and hydrogen atoms lie in the same plane, and the carbon atoms are located at the vertices of a regular hexagon with the same bond length between them, equal to 0.139 nm. All bond angles are equal to 120.
This arrangement of the carbon skeleton is due to the fact that all carbon atoms in the benzene ring have the same electron density and are in a state of sp2 hybridization.
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Goalswork: |
Study some physical and chemical properties of benzene and its homologues. Compare the reactivity of benzene and toluene. Get acquainted with the properties of polynuclear aromatic compounds using naphthalene as an example |
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Equipment and peactive assets: |
Gas outlet tube, set of test tubes, porcelain cup, three 100 ml glasses, alcohol lamp, Wurtz flask, benzene C6H6, naphthalene, concentrated sulfuric acid H2SO4, concentrated nitric acid HNO3, saturated solution of bromine water Br2, 1% solution of potassium permanganate KMnO4, sodium hydroxide NaOH, calcium chloride CaCl2. |
Experience1 . Reaction of benzene with bromine and potassium permanganate.
0.5 ml of benzene is poured into two test tubes. Add 1 ml of bromine water to one of them, and a few drops of potassium permanganate to the other. The mixture is shaken vigorously and allowed to settle.
Record observations and explain.
Synthesis."Nitration of benzene"
Descriptionwork. ABOUTtorture is carried out in a fume hood, since nitrobenzene vapors are poisonous. 25 ml of concentrated sulfuric acid H2SO4 is poured into a 100 ml flask equipped with a cooler (40-50 cm) and 20 ml of concentrated nitric acid HNO3 is carefully poured dropwise. Cool the mixture to room temperature and add 18 ml of benzene while stirring (an emulsion is formed). When nitrating benzene, make sure that the temperature of the reaction mixture does not exceed 500C and does not fall below 250C. The reaction is carried out in a water bath with a thermostat. The nitration reaction is continued for 45 minutes. at a temperature of 600C. After which the reaction mixture is cooled with cold water and separated using a separating funnel. Nitrobenzene is found at the bottom of the separatory funnel. The nitrobenzene is then washed with a dilute sodium hydroxide solution and cold water. The washed nitrobenzene is poured into a cone-shaped flask and calcined calcium chloride is added. The flask is sealed with an air-cooled stopper and heated in a water bath until a clear liquid forms. Dried nitrobenzene is poured into an air-cooled Wurtz flask and distilled at a temperature of 207-2110C. Benzene yield 22 g.
Nitrobenzene is a yellow oily liquid with the smell of bitter almonds. Nitrobenzene does not dissolve in water, but dissolves in alcohol, benzene, and ether. Molecular weight 123.11, boiling point 210.90C.
Pairs nitrobenzene poisonous, so after experiencehis must be poured into a specialwow flasksat.
Experience3 . Sulfonationaromatic hydrocarbons.
Description of the experience. Place 3 drops of toluene into two test tubes, and several naphthalene crystals into the second. 4-5 drops of concentrated sulfuric acid are poured into each test tube and heated in a boiling water bath with constant shaking for 10 minutes. Naphthalene partially sublimes and crystallizes on the walls of the test tube above the liquid level; it must be re-melted by heating the entire test tube. Note the time required to obtain a homogeneous solution.
After this, the test tube is cooled in cold water and 0.5 ml of water is added to it. If sulfonation is complete, a clear solution is formed, since sulfonic acids are highly soluble in water. Write the reaction equations for the sulfonation of toluene and naphthalene at different temperatures.
Oxygen-containing organic compounds
There are a huge number of organic compounds, which contain oxygen along with carbon and hydrogen. The oxygen atom is contained in various functional groups that determine whether a compound belongs to a particular class.
LlaboratoryJob7
Subject : "Alcohols"
Alcohols are organic substances whose molecules contain one or more hydroxo groups connected to a hydrocarbon radical.
The hydroxo group is a functional group of alcohols. Depending on the nature of the hydrocarbon radical, alcohols are divided into aliphatic (saturated and unsaturated) and cyclic.
Alcohols are classified according to various structural characteristics:
1. Based on the number of hydroxyl groups (atomicity) in the molecule, alcohols are divided into one-, two-, three-atomic, etc.
For example:
In polyhydric alcohols, primary, secondary, secondary and tertiary alcohol groups are distinguished. For example, the molecule of the trihydric alcohol glycerol contains two primary alcohol (HO-CH2-) and one secondary alcohol (-CH(OH)-) groups.
2. Depending on which carbon atom the hydroxo group is connected to, alcohols are distinguished:
primary R-CH2-OH
secondary R1 - CH - R2
tertiary R1 - C - R3
where R1, R2, R3 are hydrocarbon radicals, they can be the same or different.
3. Based on the nature of the hydrocarbon radical associated with the oxygen atom, the following alcohols are distinguished:
? limit, or alkanols containing only saturated hydrocarbon radicals in the molecule, for example,
2-methylpropanol-2
? unlimited, And or alkenols containing multiple (double or triple) bonds between carbon atoms in the molecule, for example:
CH2=CH-CH2-OH HC? C - CH - CH3
? aromatic, those. alcohols containing a benzene ring and a hydroxo group in the molecule, connected to each other not directly, but through carbon atoms, for example:
Phenylcarbinol (benzyl alcohol)
Experience1. Solubility of alcohols in water
The simplest monohydric alcohols are highly soluble in water. Solubility decreases as molecular weight increases. The solubility of polyhydric alcohols increases with increasing number of hydroxyl groups. Aqueous solutions of alcohols have a neutral environment.
Description of the experience. Pour a few drops of methyl, ethyl and isoamyl alcohol into separate test tubes and add 2-3 ml of water to each test tube. Shake it up. Note the presence or absence of layers. Draw a conclusion about the solubility of alcohols.
Test alcohol solutions with litmus paper. There is no color change. Write the structural formulas of the alcohols taken.
Control questionsand exercises:
Experience 2.Preparation of sodium alkoxide
Monohydric alcohols, as neutral compounds, do not react with aqueous solutions of alkalis. The hydrogen of the hydroxo group can only be displaced by potassium metal or sodium to form compounds called alcoholates, for example:
2C2H5OH + 2Na 2C2H5ONa + H2^
This compound is highly soluble in alcohol. When exposed to water, it decomposes to form alcohol and alkali:
C2H5ONa + H2O C2H5OH + NaOH (pH >7)
Description of the experience. A small piece of metallic sodium, purified and dried with filter paper, is thrown into a test tube with 1 ml of anhydrous ethyl alcohol, and the hole of the test tube with a gas outlet tube is closed. ( If heating causes the alcohol to boil, cool the mixture in a glass of cold water.). The released gas is ignited. If the sodium has not reacted completely, then add excess alcohol to complete the reaction.
After all the sodium has reacted, cool the test tube and add 3-4 drops of water and 1 drop of phenolphthalein. Test the solution with litmus paper. organic hydrocarbon aldehyde ketone
Experience 3.Obtaining glyceratecopper (II)
In polyhydric alcohols, the hydrogens of hydroxyl groups are more easily replaced by metals than in monohydric alcohols. Thus, for trihydric alcohols - glycerols, the corresponding metal derivatives - glycerates are obtained even when glycerol is exposed to heavy metal oxides and their hydrates, for example, copper oxide hydrate. This indicates that, unlike monohydric alcohols, polyhydric alcohols have weak acidic properties.
Description of the experience. Prepare copper(II) hydroxide. To do this, pour about 1 ml of a 10% solution of copper sulfate (CuSO4) into a test tube and add a little 10% solution of sodium hydroxide (NaOH) until a precipitate of copper hydroxide forms. Glycerol is added dropwise to the resulting precipitate and the test tube is shaken. The precipitate dissolves, resulting in a dark blue solution. Reaction equation for the formation of copper glycerate:
CuSO4 + 2NaOH Cu(OH)2v + Na2SO4
LlaboratoryJob8
Subject: « Fenolas"
Phenols called derivatives of aromatic hydrocarbons, whose molecules contain one or more hydroxyl groups -OH, directly connected with carbon atoms benzene ring.
Depending on the number of hydroxyl groups, they are distinguished: monohydric phenols and polyatomic ones.
phenol 1,2-dioxybenzene 1,3-dioxybenzene 1,4-dioxybenzene
O-dioxybenzene m-dioxybenzene P-dioxybenzene (pyrocatechol) (resorcinol) (hydroquinone)
1,2,3-trioxybenzene 1,3,5-trioxybenzene 1,2,4-trioxybenzene (pyrogallol) (fluroglucinol) (hydroxyhydroquinone)
Phenols, unlike alcohols, have weakly acidic properties. This is reflected in the fact that they easily react with alkalis, forming compounds similar to alcoholate, called phenolates. The simplest phenol is called carbolic acid. For phenols, in addition to reactions of substitution of the hydrogen-hydroxy group, reactions of substitution of hydrogen in the benzene ring are characteristic, for example, the reaction of halogenation, nitration and sulfonation. These reactions proceed more easily than in benzene, since the presence of a hydroxo group in the nucleus sharply increases the mobility of hydrogen atoms in the ortho and para positions.
Experience 1.Actionsechlorineglandonphenols
Phenols, both monohydric and polyhydric, give a characteristic color when a solution of ferric chloride is added. This reaction is quality breakdown to phenol.
INattention!Phenol is a caustic substance.When working withhimwe can't allow it Contact with skin causes burns.
Description of the experience. Add 2-3 drops of a 1% solution of iron (III) chloride to a test tube with 0.5 ml of phenol solution. Similar experiments are carried out with aqueous solutions of resorcinol, pyrogallol and hydroquinone. Solutions of phenol and resorcinol turn purple, and pyrogallol solutions turn brown-red. Hydroquinone does not give a characteristic coloring with ferric chloride, since it is easily oxidized by it to form quinone. Explain the observation. Reaction equations:
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Experience2 . Receiptphenolatesodium
Description of the experience. Pour a few ml of phenol emulsion into a test tube. Add carefully, drop by drop, sodium hydroxide solution until the phenol is completely dissolved. Sodium phenolate is formed. Add a 10% solution of sulfuric acid drop by drop to the resulting phenolate until the reaction becomes acidic. In this case, phenol will again be released in the form of an emulsion. Reaction equations:
Experience 3 . Brominationphenol.
Description of the experience. Pour 5 ml of a 1% phenol solution into a dry test tube and, with constant shaking, add a saturated solution of bromine water until a precipitate forms. Reaction equation:
LlaboratoryJob9
Subject : « Aldehydes and ketones»
Aldehydes and ketones are carbonyl compounds.
Aldehydes - This organic compounds in the molecules of which the carbon atom is a carbonyl group bonded to a hydrogen atom and a hydrocarbon radical.
General formula:
where, is the functional group of aldehydes,
R - hydrocarbon radical
Ketones - This is aboutorganic substances whose molecules contain a carbonyl group connected to two hydrocarbon radicals. General formula:
where R, R" are hydrocarbon radicals, they can be the same or different.
ethylacetic aldehyde (r) dimethylacetic aldehyde (r)
3-methylpentanal (c) secondary isobutyl acetaldehyde (p)
methylpropyl ketone (r) methyl isopropyl ketone (r)
CH3 - CH2- C - CH2 - CH3
pentanol -3 (s)
diethyl ketone (r)
Experience1. Receiptvinegaraldehydeoxidationethanol.
Description of the experience. In the flame of an alcohol lamp, a copper wire with a loop at the end is oxidized, heating it red-hot, then it is quickly lowered into a test tube with alcohol and the test tube is capped.
The copper oxide is reduced to copper metal and the alcohol is oxidized to aldehyde. Save the resulting aldehyde solution for further experiments. Reaction equation:
CH3 -CH2-OH + CuO + Cu + H2O
Experience2. Reactionsilvermirrorsonaldehyde.
Aldehydes are easily oxidized, sometimes even by atmospheric oxygen, as well as by metal oxides of silver and copper. In this case, acids with the same number of carbon atoms in the chain are formed.
The oxidation reaction of aldehydes by the action of silver oxide is the most sensitive to the aldehyde group (silver mirror reaction). The reagent is an ammonia solution of silver oxide hydrate. In this reaction, the aldehyde is oxidized to an acid, and the silver oxide is reduced to metallic silver:
2OH + 2Agv + 4NH3^ +2H2O
Ketones do not give a silver mirror reaction, since they are much more difficult to oxidize. They can be oxidized by stronger oxidizing agents, for example, potassium permanganate. In this case, the ketone molecule is split and two acid molecules are formed.
Description of the experience. A few drops of an ammonia solution of silver oxide are added to the aldehyde solution obtained in the previous experiment. The test tube is slightly heated. If the glass of the test tube is clean enough, the reduced silver is deposited on the walls in the form of a mirror. If the glass is dirty, a black precipitate of metallic silver is formed. Write the reaction equation.
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