Glycerin or, according to the international nomenclature, propanetriol -1,2,3 is a complex substance that belongs to polyhydric alcohols, or rather, it is a trihydric alcohol, because has 3 hydroxyl groups - OH. The chemical properties of glycerin are similar to those of glycerin, but are more pronounced due to the fact that there are more hydroxyl groups and they influence each other.

Glycerol, like alcohols with one hydroxyl group, is highly soluble in water. This, one might say, is also a qualitative reaction to glycerin, since it dissolves in water in almost any ratio. This property is used in the production of antifreeze - liquids that do not freeze and cool car and aircraft engines.

Glycerin also interacts with potassium permanganate. This is a qualitative reaction to glycerin, which is also called the Scheele volcano. To carry it out, you need to add 1-2 drops of anhydrous glycerin to the potassium permanganate powder, which is poured in the form of a slide with a depression in a porcelain bowl. After a minute, the mixture spontaneously ignites. During the reaction, a large amount of heat is released, and hot particles of reaction products and water vapor fly away. This reaction is redox.

Glycerin is hygroscopic, i.e. able to retain moisture. It is on this property that the following qualitative reaction to glycerin is based. It is carried out in a fume hood. To carry it out, pour approximately 1 cm3 of crystalline potassium hydrogen sulfate (KHSO4) into a clean, dry test tube. Add 1-2 drops of glycerin, then heat until a pungent odor appears. Potassium hydrogen sulfate acts here as a water-absorbing substance, which begins to manifest itself when heated. Glycerin, losing water, is converted into an unsaturated compound - acrolein, which has a sharp, unpleasant odor. C3H5(OH)3 - H2C=CH-CHO + 2 H2O.

The reaction of glycerol with copper hydroxide is qualitative and serves to determine not only glycerol, but also others. In order to carry it out, it is initially necessary to prepare a fresh solution of copper (II) hydroxide. To do this, we add copper (II) hydroxide, which forms a blue precipitate. We add a few drops of glycerin to this test tube with the sediment and notice that the sediment has disappeared and the solution has acquired a blue color.

The resulting complex is called copper alcoholate or glycerate. A qualitative reaction to glycerin with copper (II) hydroxide is used if the glycerin is in pure form or in an aqueous solution. To carry out such reactions in which glycerin is present with impurities, it is necessary to preliminarily purify it from them.

Qualitative reactions to glycerol help detect it in any environment. It is actively used for the determination of glycerol in food, cosmetics, perfumes, medicines and antifreezes.

Glycerin – trihydric alcohol:

Glycerin is a colorless, syrupy liquid with a sweetish taste, highly soluble in water, and hygroscopic. Glycerin is obtained by breaking down fats.

Chemical properties.

1. Interaction with alkali metals

2. Interaction with hydrogen halides

3. Esterification reaction (nitration-reaction with nitric acid)

4. Qualitative reaction to polyhydric alcohol

A blue copper glycerate solution is formed.

Application of glycerin

Glycerin is used as a food additive E422 in the production of confectionery products to improve consistency, prevent chocolate from sagging, and increase the volume of bread.
Its addition reduces the time it takes for bread products to go stale, makes pasta less sticky, and reduces the adhesion of starch during baking.

It is used in the production of extracts of coffee, tea, ginger and other plant substances, which are finely ground and treated with an aqueous solution of glycerin, heated and evaporated water. The result is an extract containing about 30% of it.

Glycerin is widely used in the production of soft drinks. An extract prepared on its basis, when diluted, gives drinks “softness”.

Due to its high hygroscopicity, it is used when preparing tobacco (to keep the leaves moist and eliminate the unpleasant taste).

This substance is used quite often in cosmetics, especially for hand creams: in almost every similar “mass” product you can find glycerin in its composition. But cosmetic companies sometimes add it to face cream, which causes indignation among many women: they say, glycerin is an alcohol, and all alcohols ultimately dry out the skin. However, we now know that it is better to use cosmetics with glycerin while taking a bath, where there is high humidity: it is in such conditions that you can achieve maximum skin hydration with the help of this trihydric alcohol. Another great opportunity to use glycerin is to apply cream to the skin during bath procedures.
It is important to take into account that if you prepare homemade cosmetics using glycerin, then its concentration should not exceed 5-7%, because When used undiluted, glycerin actually dries out the skin.

But there are opinions that the use of glycerin is harmful to the skin, creating only the external effect of moisturizing it. But in fact, glycerin contributes to even greater drying of the skin, drawing moisture from its deep layers and simply holding it on the surface.



Polyhydric alcohols- these are organic compounds whose molecules contain two or more hydroxyl groups connected to a hydrocarbon radical.
OH groups in polyhydric alcohols are located at different carbon atoms:

Compounds with two OH groups on one carbon atom are unstable. They split off water and turn into aldehydes:

Compounds with two OH groups at adjacent carbon atoms are called glycols (or diols).

Receipt

Glycols are produced by the oxidation of alkenes in an aqueous medium. For example, under the action of potassium permanganate or atmospheric oxygen in the presence of a silver catalyst, alkenes are converted into dihydric alcohols:

Another way to obtain polyhydric alcohols is the hydrolysis of halogenated hydrocarbons:

In production, glycerin is obtained according to the following scheme:

Physical properties

Ethylene glycol and glycerin are colorless viscous liquids with a sweet taste (from the Greek - sweet). Solubility in water is unlimited. The boiling point of ethylene glycol is 197.2 °C, glycerin is 290 °C. Ethylene glycol is poison.

Chemical properties

Ethylene glycol and glycerin are similar to monohydric alcohols.
So, they react with active metals:

Polyhydric alcohols in reaction with hydrogen halides exchange one or more OH hydroxyl groups for halogen atoms:

Glycerol interacts with nitric acid with the formation of esters. Depending on the reaction conditions (molar ratio of reagents, catalyst concentration - sulfuric acid and temperature) mono-, di- and trinitroglycerides are obtained:

Qualitative reaction of polyhydric alcohols A method that allows one to distinguish compounds of this class is interaction with freshly prepared copper(II) hydroxide. In an alkaline medium with a sufficient concentration of glycerol, the blue precipitate of Cu(OH) 2 dissolves to form a bright blue solution - copper(II) glycolate:

EXERCISES.

1. Underline the structural formulas of polyhydric alcohols:

ClCH 2 CH 2 Cl, NOS 3 H 7, NOCH 2 CH 2 OH, C 2 H 6 O 2,

HOCH 2 COOH, HOCH 2 CH 2 CH 2 OH, CH 3 OCH 2 CH 2 OH.

2. Using the names of the substances, make up their structural formulas:

a) ethanediol-1,2; b) ethylene glycol; c) propanediol-1,2, d) propanediol-1,3;
e) glycerin; e) butanetriol-1,2,4.

3. Write down reaction equations for producing ethylene glycol from:
a) ethylene; b) 1,2-dibromoethane.

4. List five applications of polyhydric alcohols (ethylene glycol and glycerol).

5. Write reaction equations for a chain of chemical transformations, name the organic substances:

6. Make a chain of chemical transformations to obtain dihydric alcohol
CH 3 CHONCH 2 OH from alkane C 3 H 8 . Use the diagram:
saturated hydrocarbon monohalohydrocarbon unsaturated hydrocarbon dihalohydrocarbon dihydric alcohol.

Answers to exercises for topic 2

Lesson 20

1. The structural formulas of polyhydric alcohols are underlined:

2. Structural formulas compiled by the names of substances:

3. Reactions for producing ethylene glycol:

4. Five areas of application of polyhydric alcohols.

Ethylene glycol(EG) – in antifreezes, 66% EG freezes at –60 °C;
in the synthesis of lavsan [–CH 2 CH 2 O(O)CC(O)O–] n;
solvent ( t kip = 198 °C).

Glycerol– in perfumery, cosmetics, medicine – solvent, component of ointments;
for the production of trinitroglycerin - an explosive and a drug that dilates blood vessels.

5. Reactions for a chain of chemical transformations:

6. A chain of chemical transformations of the alkane C 3 H 8 into propylene glycol CH 3 CHOHCH 2 OH through intermediate substances of given classes.

is a colorless, viscous liquid, the simplest trihydric alcohol. Non-toxic, odorless, sweet in taste, which is why it got its name (glycos - sweet). It dissolves in all proportions in water and alcohol, is almost insoluble in ether, carbon disulfide, chloroform, fatty and essential oils and gasoline, and is highly hygroscopic.
Glycerol reacts readily with many organic and inorganic compounds to form esters, aliphatic and aromatic ethers and metal glycerides (glycerates).
Density 1.261 g/cm³. Melting point - 18° C, boiling point - 290° C.

Chemical formula: C 3 H 5 (OH) 3

Glycerin is obtained as a by-product of soap production. Most synthetic methods for producing glycerin are based on the use of propylene as a starting product.
The following types of glycerin are produced by industry: natural raw glycerin of the 1st, 2nd and 3rd grades (GOST 6823-2000) and distilled premium grade, 1st and 2nd grade (GOST 6824-96).

Use of glycerin (1, 2, 3-trihydroxypropane, 1, 2, 3-propanetriol).
Warfare.
Glycerin is used to produce nitroglycerin, from which dynamite, smokeless powder and other explosives used for peaceful purposes and military purposes are produced, used as antifreeze solutions in various engines, brake and heating fluids, and for cooling gun barrels.
Tobacco industry.
Due to its high hygroscopicity, glycerin is used to regulate the moisture content of tobacco in order to eliminate the unpleasant irritating taste.
Production of plastics.
Glycerin is a valuable component in the production of plastics and resins. Glycerol ethers are widely used in the production of transparent packaging materials. For example, cellophane has excellent flexibility and does not lose its properties in either heat or cold.
Food industry.
Glycerin (food additive E422) is used to prepare extracts of tea, coffee, ginger and other plant substances, which are crushed, moistened and treated with glycerin, heated and extracted with water to obtain an extract containing about 30% glycerol. Glycerin is widely used in the production of soft drinks. Glycerin is used in the production of mustard, jelly and vinegar.
Agriculture.
Glycerin is used when treating seeds and seedlings. Dilute solutions of glycerin help the germination of oats and other grains.
Medical industry.
Glycerin is widely used in medicine and the production of pharmaceuticals. Glycerin has antiseptic properties, so it is used to prevent wound infection.
Electrical and radio engineering.
In radio engineering, glycerin is widely used in the production of electrolytic capacitors. Glycerin is used in the production of alkyd resins, which are used as an insulating material.
Textile, paper and leather industries.
Glycerin in the textile industry is used in spinning, weaving, printing, dyeing and sizing. Glycerin gives fabrics elasticity and softness. It is used to produce aniline dyes, paint solvents, and also as an antiseptic and hygroscopic additive to printing inks. Glycerin is widely used in the production of synthetic silk and wool.
In the paper industry, glycerin is used in the production of tracing paper, parchment, tissue paper, paper napkins and greaseproof paper.
In the leather industry, glycerin is added to aqueous solutions of barium chloride, which is used as a preparation for preserving leather. Glycerin is one of the components of wax emulsions for tanning leather.
Paint and varnish industry.
Glycerin is a valuable component of polishing compounds, especially varnishes used for final finishing.
Production of detergents and cosmetics.
A large number of varieties of toilet soap contain glycerin, which enhances its washing ability, makes the skin white and softens it. Glycerin soap helps remove colorants from sun-tanned skin. In cosmetics, polyols are used as humectants. Glycerin is a natural product obtained from the hydrolysis of vegetable oils. Possessing hygroscopic properties, it moisturizes the skin, giving it softness and elasticity.
Other applications.
For the manufacture of putties, hectographic mass, copying ink, stamp inks, in leatherworking and for other purposes.

Physico-chemical characteristics of crude glycerin GOST 6823-2000:

Indicator name	Norm for varieties
	first	second	third
			brand 1	brand 2
Mass fraction of pure glycerin, %, not less	86	86	82	78
Reaction of glycerol, cm³ 0.1 mol/dm³ (0.1 N) HCl or KOH solution, no more	6,0	6,0	6,0	6,0
Mass fraction of ash, %, no more	0,35	1,80	3,00	9,50
Mass fraction of non-volatile organic residue, no more	0,85	2,0	3,0	4,0
Fatty acids and resins (qualitative reaction)	Absence		Footprints
Sulfuric acid compounds (sulfates) (qualitative reaction)	Same		Same
Reaction to surfactants in glycerin, cm³ 0.1 mol/dm³ (0.1 N) HCl solution, no more	2,0	5,0	6,0	Not standardized
Protein substances in glycerol entering distillation (qualitative reaction)	Absence			Same

Safety requirements.
Crude glycerin is a flammable, non-toxic product.
Glycerin is thermally unstable; with prolonged heating (even up to 90-130° C) it decomposes to form flammable substances (acrolein, acetone), which reduce the flash point to 112° C.
It is not allowed to use open fire in places where raw glycerin is stored and where work is carried out with it.
Production premises in which work with crude glycerin is carried out must be equipped with supply and exhaust ventilation.

Glycerol. Properties. Application. Impact.

Glycerol- trihydric alcohol is a viscous, heavy liquid, colorless and odorless. Sweet to taste. Hygroscopic. Mixes with water in any ratio. The melting point of glycerin is 18°C, the boiling point is 260°C. Density - 1.26 g/s m³, viscosity 1.49 Pa*s (reduction 8.94 * 10-4 Pa*s, for propylene glycol 0.056 Pa*s). The bulk of glycerin obtained as a by-product from saponification of fats. Part of glycerin get from synthetic raw materials. Currently, industrial production of synthetic glycerin from non-food raw materials has been carried out - mainly based on propylene. Glycerin can also be obtained from starch hydrolysis products, wood flour, etc. and hydrogenation of the resulting monosaccharides or glycol fermentation of sugars (hexoses). The process can occur in a sulfite or alkali environment (pH 7.0 or higher). Shelf life of glycerin - 5 years. Recognized as harmless agent used in the food and medical industries.

Application:

The areas of application of glycerin are varied: food industry, tobacco production, medical industry, production of detergents and cosmetics, agriculture, textile, paper and leather industries, plastics production, paint and varnish industry, electrical engineering and radio engineering.

• Glycerin is used as a food additive E 422 in production confectionery to improve consistency, to prevent chocolate from sagging, to increase bread volume. Adding it reduces time staleness of bread products, makes pasta less sticky, reduces starch sticking during baking. Applicable during production coffee, tea, ginger extracts and other plant substances, which are finely ground and treated with an aqueous solution of glycerin, heated and the water evaporated. It turns out an extract, which contains about 30%.Glycerin is widely used in production soft drinks. The extract prepared on its basis, in a diluted state, gives drinks "softness".

• Because of its high hygroscopicity it is used for tobacco procurement(to keep leaves moist and eliminate bad taste).

• IN medicine and in production pharmaceuticals it is used to dissolve drugs, increase the viscosity of liquid preparations, protect against changes during fermentation of liquids, and prevent drying of ointments, pastes and creams. Using it instead of water, you can prepare highly concentrated medical solutions. It also dissolves iodine, bromine, phenol, thymol, mercuric chloride and alkaloids well, and has antiseptic properties.

• Glycerin enhances cleaning ability of most grades toilet soap in which it is used, it gives the skin whiteness and softens it.

• IN agriculture it is used to treat seeds, which promotes their good germination, trees and shrubs, which protects the bark from bad weather.

• IN textile industry used in weaving, spinning, dyeing, which gives fabrics softness and elasticity. It is used to produce aniline dyes, paint solvents, and in the production of synthetic silk and wool.

• IN paper industry It is used in the production of tissue paper, parchment, tracing paper, paper napkins and heat-resistant paper.

• IN leather industry Glycerin solutions are used in the process of fattening leather, adding it to aqueous solutions of barium chloride. It is included in wax emulsions for tanning leather.

• Glycerin is widely used in production transparent packaging materials. Due to its plasticity, ability to retain moisture and withstand cold, it is used as a plasticizer in the production of cellophane. It is also an integral part in the production of plastics and resins. Polyglycerols are used to coat paper bags in which oil is stored. Paper packaging material becomes fire-resistant if it is impregnated under pressure with an aqueous solution of glycerin, borax, ammonium phosphate, and gelatin.

• IN paint industry 1,2,3-propanetriol is a constituent of polishing compounds, especially varnishes used for final finishing.

• IN radio engineering it is widely used in the production of electrolytic capacitors, alkyd resins, which are used as an insulating material, in the processing of aluminum and its alloys.

· Application of glycerin in medicine

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· Glycerin is a colorless, viscous liquid, odorless, but sweetish in taste. The property of Glycerin is its excellent miscibility with water, is not a toxic substance, soluble in alcohol, but insoluble in chloroform, fats and ether.

· Therefore, the use of Glycerin in medicine has become widespread. It is indispensable in the production of many pharmaceuticals. For example, thanks to its properties, it is possible to increase the viscosity of a drug or, conversely, to dissolve a drug.

· Medical ointments, creams and pastes Glycerin protects them from rapid drying, disinfects them, having antiseptic properties.

· Rectal suppositories are also made on the basis of Glycerin, which are used for constipation of various types, helping to empty the intestines.

· Due to its viscous consistency, the use of Glycerin in medicine also covers such areas as the production of mixtures, tinctures, rinses, the action of which is aimed at enveloping a sore throat, moisturizing and softening it, to relieve coughing attacks.

· Glycerin, due to its antiseptic properties, is used in medicine to prevent skin wounds from becoming infected.

· Preservation of skin moisture is also possible thanks to Glycerin. Added to various medicinal creams and ointments, it treats skin problems, leaving the skin moisturized, elastic and soft, and has protective and restorative properties.

· Capable of dissolving mercuric chloride, iodine, bromine, alkaloids, phenol, tannin, Glycerin, unlike water, allows one to obtain highly concentrated solutions of these compounds.

Physico-chemical properties of glycerin and its use

Good afternoon friends! Today we will talk about an amazing substance - glycerin.

Glycerin is a fairly common substance. It can be found in many medicines, ointments, creams, soap and even in shampoos.

How to get it and where to use it

The bulk of glycerin is obtained as a by-product during the saponification of fats.

The scope of glycerin is extensive. It is used in many industries: medical, tobacco, textile, paper, paint and varnish industries, in the production of household chemicals, electronics, radio equipment, etc.

Glycerin, whose properties are so diverse, is widely used at home. For example, in the treatment of skin diseases and burns, it is effective for coughs, has laxative properties, and is the simplest moisturizer.

The most common recipes for using glycerin at home:

§ use of glycerin in everyday life;

§ the use of glycerin in hair care;

§ secrets and recipes for an “unpopping” soap bubble.

Let us consider the physical and chemical properties of this amazing substance in more detail.

Chemical properties

The chemical properties of glycerin are the same as those of other polyhydric alcohols. And these are not all the properties of glycerin. One of the advantages of using glycerin is its low price and availability, so its unique properties can be easily used at home. Glycerin can be purchased in pharmacies or online stores.

Let's look at the main properties of glycerin, which will be useful when using glycerin at home.

Physical properties

Medical glycerin is a colorless, viscous liquid, odorless, and sweet in taste. That is why it got its name (“glycos” in Greek - sweet). Glycerin is non-toxic, soluble in water in any quantity, and is a good solvent for inorganic salts, alkali, mono- and disaccharides.