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General information Rational Formula: C3H5(OH)3 Density: 1.261 g/cm³ Melting Point: 18°C ​​Boiling Point: 290°C

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Discovery History Glycerin was discovered in 1779 by the Swedish researcher Carl Scheele, who discovered that when olive oil was heated with lead oxide, a sweet taste solution was formed. Further evaporation of the solution allowed him to obtain a syrupy heavy liquid. In 1811, Michel Eugene Chevrel, a French organic chemist, while studying the composition of a sweet viscous liquid, first named it glycerin. Chemical composition installed by Pelouze in 1836.

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Methods of obtaining Glycerin was first obtained in 1779 by Scheele during the saponification of fats in the presence of lead oxides. The bulk of glycerol is obtained as a by-product during the saponification of fats. Most synthetic methods for the production of glycerin are based on the use of propylene as the starting product. By chlorination of propylene at 450-500 ° C, allyl chloride is obtained, when hypochlorous acid is added to the latter, chlorohydrins are formed, which, when saponified with alkali, turn into glycerol. Other methods are based on the conversion of allyl chloride to glycerol via dichlorohydrin or allyl alcohol. There is also a method for obtaining glycerin by the oxidation of propylene to acrolein; passing a mixture of vapors of acrolein and isopropyl alcohol through a mixed ZnO - MgO catalyst forms allyl alcohol. It at 60-70 ° C in an aqueous solution of hydrogen peroxide turns into glycerin. Glycerin can also be obtained from the products of hydrolysis of starch, wood flour, hydrogenation of the formed monosaccharides or glycolic fermentation of sugars.

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Physical properties Glycerin is a colorless, viscous, highly hygroscopic liquid, miscible with water in any proportion. It tastes sweet, which is why it got its name (ancient Greek γλυκύς - sweet).

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Chemical properties 1. In 1846, the Italian chemist Ascanio Sobrero heated glycerin with a mixture of sulfuric and nitric acids. The resulting product, when isolated, exploded with great force. This is how glycerol trinitrate was discovered. 2. Interaction with hydrogen halides: The interaction of glycerol with hydrogen halides or phosphorus halides leads to the formation of mono- and dihalohydrins. CH2OH-CHOH-CH2OH + HCl → CH2OH-CHOH-CH2Cl + H2O

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Chemical properties 3. Qualitative reaction: 4. When dehydrated, it forms toxic acrolein: HOCH2CH(OH)-CH2OH→H2C=CH-CHO + 2 H2O and is oxidized to glyceraldehyde CH2OHCHOHCHO, dihydroxyacetone CH2OHCOCH2OH or glyceric acid CH2OHCHOHCOOH.

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Application The scope of glycerin is diverse: food industry, tobacco industry, medical industry, production of detergents and cosmetics, Agriculture, textile, paper and leather industries, plastics, paint and varnish industry, electrical and radio engineering (as a flux for soldering). Glycerin belongs to the group of stabilizers that have the properties to maintain and increase the degree of viscosity, as well as the consistency of food products. Registered as a food additive E422, and is used as an emulsifier, with which various immiscible mixtures are mixed. Since glycerin lends itself well to gelation, unlike, for example, ethanol, and, like ethanol, it burns without smell and fumes, it is used to make high-quality transparent candles. Glycerin is also used in the manufacture of dynamite.

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Military Glycerin is used to produce nitroglycerin, which is used to make dynamite, smokeless powder, and other explosives. They are used as antifreeze solutions in various engines, brake and heating fluids, for cooling gun barrels.

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Tobacco industry Due to its high hygroscopicity, glycerin is used to control the moisture content of tobacco in order to eliminate the unpleasant irritating taste.

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Plastics production Glycerin is valuable integral part in the production of plastics and resins. Glycerol esters are widely used in the production of transparent packaging materials.

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Food industry Glycerin is used to prepare extracts of tea, coffee, ginger and other plant substances, which are crushed, moistened and processed with glycerin, heated and extracted with water to obtain an extract containing about 30% glycerin.

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Medical industry Glycerin is widely used in medicine and pharmaceuticals. Glycerin has antiseptic properties, so it is used to prevent infection of wounds.

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Class: 10

Class: Grade 10

Lesson type: lesson learning new material

The purpose of the lesson: understand the concept of polyhydric alcohols

Lesson objectives:

• Educational: reveal the dependence: composition -> structure -> properties -> use of glycerin
• Developing: continue the formation of skills: observe physical and chemical phenomena, explain the observed phenomena.
• Educational: the formation of interest in the subject

Used Literature: Rudziti with G.E., Feldman F.G. Organic chemistry, Grade 10

Used equipment:

• Reagents: copper (II) sulfate solutions, crystalline sodium, glycerin, water, sodium chloride, snow
• Equipment: media projector, presentation, test tubes, filter paper, spirit lamp, matches, splinter

During the classes

I. Organizing time: greetings

II. Updating of reference ZUN

Oral frontal conversation

What are alcohols? (Alcohols are derivatives of hydrocarbons, in the molecules of which one or more hydrogen atoms are replaced by hydroxyl groups)

What is the general formula for monohydric alcohols? (C n H2 n+1 OH)

What types of isomerism are characteristic of alcohols? ( Isomerism of the carbon skeleton, isomerism of the position of the hydroxyl group)

How are alcohols named? ( The names are derived from the names of the corresponding hydrocarbons with the addition of the suffix -ol)

III. Logical transition to new material. Definition of the topic and purpose of the lesson.

Alcohol classification

Monoatomic Polyatomic

Polyhydric alcohols are organic compounds whose molecules contain several hydroxyl groups connected to hydrocarbon radicals.

CH 2 OH-CH 2 OH - ethanediol-1,2, ethylene glycol

CH 2 OH-CHOH-CH 2 OH - propanetriol - 1,2,3, glycerin

The purpose of the lesson: consider glycerin, its physical and chemical properties, methods for its preparation and application

Definition of the topic of the lesson ( Glycerol)

IV. Formation of new ZUN

1. Obtaining glycerin

For the first time, glycerin was received by K. V. Scheele (1779) and again by M.E. Chevrel (1813).

In the laboratory, glycerin is obtained from the halogen derivatives of the corresponding hydrocarbons.

CH 2 Cl - CHCl-CH 2 Cl + 3H2O -> 2CH 2 OH - CHOH-CH 2 OH + 3HCl

To shift the reaction equilibrium to the right. eye-catching hydrochloric acid neutralized with alkali.

Glycerin in production is obtained from propylene, which is formed during the cracking and pyrolysis of oil, as well as from fats.

C 3 H 5 (OS 17 H 35) 3 + 3H 2 O -> CH 2 OH - CHOH - CH 2 OH + 3C 17 H 35 COOH

2. Physical properties

Glycerin is a colorless syrupy liquid with a sweetish taste, it dissolves well in water and ethanol, boils at a temperature of 290 0 C, and is hygroscopic.

Experience number 1. Lowering the freezing point of aqueous solutions of glycerin.

Pour 5 ml of glycerin into a test tube and the same volume of magenta-tinted water is gradually layered on top, shake. Place the test tube into the cooling mixture (a mixture of snow and solid sodium chloride), and simultaneously place the test tube with water into the mixture.

Questions during the demo:

What are you watching? (liquid becomes homogeneous and colored)

What conclusion can be drawn from the experience? (Glycerine is an antifreeze and can be used as an antifreeze for engine coolants)

Experience number 2. Hygroscopicity of glycerin

Put a few drops of water on a sheet of filter paper, a few drops of glycerin on the second sheet. Leave for a while.

3. Chemical properties.

The chemical properties of glycerin are similar to those of monohydric alcohols.

1. Interaction with crystalline sodium

Experience 3. Reaction with sodium

Pour 2-3 ml of glycerol into a test tube, dip metallic sodium the size of a pea into the solution. Heat the test tube slightly, ignite the gas released.

Questions during the demonstration

What are you watching? ( gas is released, charring)

What gas is released? ( hydrogen, because the splinter burns with a blue flame)

2CH 2 OH - CHOH-CH 2 OH + 6Na -> 2CH 2 ONa -CHONa-CH 2 ONa + 3H 2

sodium glycerate

Interaction with copper (II) hydroxide in the presence of alkali. The precipitate dissolves and a bright blue solution is formed - copper glycerate.

Experience 4. Pour sodium hydroxide into a test tube and add copper sulfate dropwise until a precipitate forms, add glycerin to the resulting precipitate.

The reaction equation is given in a simplified form, because compounds of a more complex composition are simultaneously formed. This reaction proves that polyhydric alcohols have weak acidic properties. This reaction is qualitative for polyhydric alcohols.

An increase in the number of hydroxyl groups in the molecules of polyhydric alcohols gives greater mobility to hydrogen atoms compared to monohydric alcohols. This is the result of the mutual influence of hydroxyl groups on each other.

4. Interaction with nitric acid.

As a result, nitroglycerin is formed - an ester of nitric acid and glycerol.

For practical application nitroglycerin, it is converted into dynamite by impregnating diatomaceous earth or wood flour with nitroglycerin. The author of dynamite is A. Nobel

CH 2 OH - CHOH - CH 2 OH + 3HNO 3 -> CH 2 ONO 2 - CHONO 2 - CH 2 ONO 2 + 3H 2 O

1,2,3 - trinitroglycerin

Interaction with hydrogen halides

CH 2 OH - CHOH - CH 2 OH + 3HCl -> CH 2 Cl - CHCl - CH 2 Cl + 3H2O

1,2,3 - trichloropropane

5. Application

Glycerin is used to produce nitroglycerin and dynamite. Glycerin is used in perfumery and medicine (for the manufacture of ointments that soften the skin), in the leather industry (to protect the skin from drying out), in the textile industry (to make fabrics soft and elastic). In medicine, a 1% solution of nitroglycerin in alcohol serves as one of the means that dilates blood vessels.

6. Genetic relationship of polyhydric alcohols with other classes of organic compounds

Back to the filter paper experience

What are you watching? ( paper with water dried up, and with glycerin it became even more important)

What can be said about glycerin? (glycerin can absorb moisture, thereby moistening objects).

V. Consolidation.

Reveal the genetic blueprint

VI. Message d/z: paragraph 24

So, today in the lesson we got acquainted with polyhydric alcohols using the example of glycerin, examined its physical and chemical properties, methods of preparation and application. This lesson is over.

Glycerol
1. Formula | HOCH2-CH(OH)-CH2OH
2. alternate names | 1,2,3-propanetriol | 1,2,3-trihydroxypropane | glycerine
glycerine glycol alcohol | propanetriol
3. Mass fractions| C 39.1% | H 8.76% | About 52.1%

"Structure of esters" - Definition of the class of esters. Fats do not dissolve in water. chemically active substances. Solvents. Hydrogenation. Energy source. Derivatives of carboxylic acids. Fats. Liquids. Complex ethers.

"Properties and uses of fats" - Determination of the unsaturation of fats. received product. German scientist. Fats are the main source of energy for living organisms. Glycerol. The use of fats. Getting soap. The chemical composition of fats. Chemical properties of fats. A mixture of esters. cocoa beans. Desert ships. Fat hydrolysis reaction equation.

"Esters" - New antifog. Nitroglycerine. Structure. Obtaining esters. Esters of fatty acids. Tishchenko Vyacheslav Evgenievich. Connections. Picture. Discovery of esters. Classification and composition of esters. Esters are isomeric. Structural isomerism. Oils. Hydrogen atom. Machine oil. Derivatives of carboxylic acids.

"The use of fats" - Paint. Perfumery. Glycerol. The use of fats. How much and what kind of fat a person needs. Candles. Fats. Animal food. Soap. The sweet is better than the fat. Chocolate. Propolis.

"Chemistry of Fats Grade 10" - Conclusion: Strong acids displace weak acids from salt solutions. Plan. Complex ethers. Name substances. Fats. Laboratory experiment No. 1 “The action of strong acids on soap” L. 1. Poll on the topic “Carboxylic acids” Option No. 1. Stearic acid. carb properties. to-t, similar to mineral, on the example of acetic acid.

"Esters and Fats" - Ester of acids and glycerol. Esters have a large practical value. Lesson plan. 3. Fats. Fats are essential food. Fats. The role of fats in life. This is how carboxylic acids interact with alcohols. To shift the equilibrium to the right, it is necessary to remove water or ether. Vegetable fats are called oils.

• Polyhydric alcohols - These are organic compounds whose molecules contain two or more hydroxyl groups connected to a hydrocarbon radical .

Alcohols containing two OH groups are called diatomic.

Their general formula With P H 2p (IS HE) 2

Alcohols containing three OH groups are called triatomic.

Their general formula With P H 2p-1 (IS HE) 3

Name glycols - due to the sweet taste of the first representative of the series - glycol (from the Greek "glycos" - sweet). According to the IUPAC nomenclature, these alcohols are called alkanediols.

The simplest representative of alkanediols is an alcohol of the composition HO-CH 2 CH 2 -OH , so-called ethylene glycol or ethanediol .

The simplest trihydric alcohol is glycerin or propanetriol.

Structure

Polyhydric alcohols are similar in molecular structure to monohydric alcohols. The difference lies in that their molecules contain several hydroxyl groups. The oxygen they contain shifts the electron density away from the hydrogen atoms. This is what leads to an increase in the mobility of hydrogen atoms and an increase in acidic properties.

Physical Properties

Ethylene glycol representative of dihydric alcohols -glycols.

Syrup-like liquid of sweetish taste, odorless, poisonous.

It mixes well with water and alcohol, it is hygroscopic.

Glycerol- representative of trihydric alcohols - glycerols .

Colorless, viscous, hygroscopic liquid, sweet in taste.

Miscible with water in any ratio.

Receipt

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

Receipt

• Another way to obtain polyhydric alcohols is the hydrolysis of halogen derivatives of hydrocarbons:

Receipt

In production, glycerin is obtained according to the scheme:

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

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

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

• A qualitative reaction of polyhydric alcohols, which makes it possible to distinguish compounds of this class, is the interaction with freshly prepared copper(II) hydroxide. In an alkaline environment with a sufficient concentration of glycerol, a blue precipitate of Cu (OH) 2 dissolves to form a bright blue solution - copper (II) glycolate:

• An important property of ethylene glycol is the ability to lower the freezing point of water, from which the substance has found wide application as a component of automotive antifreeze and antifreeze fluids.
• It is used to obtain lavsan (a valuable synthetic fiber).

Application of glycerin

Glycerol finds wide application in cosmetics, Food Industry, pharmacology, production of explosives. Pure nitroglycerin explodes even with a slight impact; it serves as a raw material for obtaining smokeless powders and dynamite - an explosive