Esters structural features. Esters. Fats. Formation of oxonium compounds

Send your good work in the knowledge base is simple. Use the form below

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

Posted on http://www.allbest.ru/

Ministry of Health of the Sverdlovsk Region

Pharmaceutical branch of GBOU SPO "SOMK"

Department of Chemistry and Pharmaceutical Technology

Esters in everyday life

Petrukhina Marina Alexandrovna

Supervisor:

Glavatskikh Tatiana Vladimirovna

Ekaterinburg

Introduction

2. Physical properties

5. Esters in perfumery

9. Obtaining soap

Conclusion

Introduction

Slomzhy ethers are derivatives of oxo acids (both carboxylic and mineral, in which the hydrogen atom in the OH group is replaced by an organic group R (aliphatic, alkenyl, aromatic or heteroaromatic); they are also considered as acyl derivatives of alcohols.

Most of the studied and widely used esters are compounds derived from carboxylic acids. Esters based on mineral (inorganic) acids are not so diverse, because the class of mineral acids is less numerous than carboxylic acids (the variety of compounds is one of the distinguishing features of organic chemistry).

Targets and goals

1. Find out how widely esters are used in everyday life. Spheres of application of esters in human life.

2. Describe the various methods for producing esters.

3. Find out how safe it is to use esters in everyday life.

Subject of study

Esters. Methods for obtaining them. The use of esters.

1. The main methods of obtaining esters

Esterification is the interaction of acids and alcohols under conditions of acid catalysis, for example, the production of ethyl acetate from acetic acid and ethyl alcohol:

The esterification reactions are reversible; a shift in equilibrium towards the formation of target products is achieved by removing one of the products from the reaction mixture (most often by distilling off more volatile alcohol, ether, acid or water).

Reaction of anhydrides or halides of carboxylic acids with alcohols

Example: Getting ethyl acetate from acetic anhydride and ethyl alcohol:

(CH3CO) 2O + 2 C2H5OH = 2 CH3COOC2H5 + H2O

Interaction of acid salts with haloalkanes

RCOOMe + R "Hal = RCOOR" + MeHal

Attachment of carboxylic acids to alkenes under acid catalysis conditions:

RCOOH + R "CH = CHR" "= RCOOCHR" CH2R ""

Alcoholysis of nitriles in the presence of acids:

RC + = NH + R "OH RC (OR") = N + H2

RC (OR ") = N + H2 + H2O RCOOR" + + NH4

2. Physical properties

If the number of carbon atoms in the starting carboxylic acid and alcohol does not exceed 6-8, then the corresponding esters are colorless oily liquids, most often with a fruity odor. They make up the fruity ester group.

If an aromatic alcohol (containing an aromatic nucleus) participates in the formation of an ester, then such compounds usually have a floral rather than a fruity odor. All compounds of this group are practically insoluble in water, but readily soluble in most organic solvents. These compounds are interesting for a wide range of pleasant aromas, some of them were initially isolated from plants, and later synthesized artificially.

With an increase in the size of the organic groups that make up the esters, up to C15-30, the compounds acquire the consistency of plastic, easily softening substances. This group is called waxes and is generally odorless. Beeswax contains a mixture of various esters, one of the components of the wax, which we managed to isolate and determine its composition, is palmitic acid myricyl ester С15Н31СООС31Н63. Chinese wax (product of isolation of cochineal - insects of East Asia) contains ceryl ester of cerotinic acid С25Н51СООС26Н53. Waxes are not wetted with water, soluble in gasoline, chloroform, benzene.

3. Some information about individual representatives of the class esters

Esters of formic acid

HCOOCH3 - methyl formate, bp = 32 ° C; solvent for fats, mineral and vegetable oils, cellulose, fatty acids; an acylating agent; used in the production of some urethanes, formamide.

HCOOC2H5 - ethyl formate, bp = 53 ° C; cellulose nitrate and acetate solvent; an acylating agent; perfume for soap, it is added to some types of rum to give it a characteristic aroma; used in the production of vitamins B1, A, E.

HCOOCH2CH (CH3) 2 isobutyl formate; somewhat resembles the smell of raspberries.

HCOOCH2CH2CH (CH3) 2 - isoamyl formate (isopentyl formate), a solvent for resins and nitrocellulose.

HCOOCH2C6H5 - benzyl formate, bp = 202 ° C; has a jasmine scent; used as a solvent for varnishes and dyes.

HCOOCH2CH2C6H5 - 2-phenylethylformate; has the smell of chrysanthemums.

Acetic acid esters

CH3COOCH3 - methyl acetate, bp = 58 ° C; in terms of dissolving ability it is similar to acetone and is used in some cases as its substitute, however, it is more toxic than acetone.

CH3COOC2H5 - ethyl acetate, boiling point = 78 ° C; dissolves most polymers like acetone. Compared to acetone, it has the advantage of a higher boiling point (less volatility).

CH3COOC3H7 - n-propyl acetate, bp = 102 ° C; dissolving power is similar to ethyl acetate.

CH3COOC5H11 - n-amyl acetate (n-pentyl acetate), bp = 148 ° C; resembles a pear in smell, it is used as a solvent for varnishes, since it evaporates more slowly than ethyl acetate.

CH3COOCH2CH2CH (CH3) 2 - isoamyl acetate (isopentyl acetate), used as a component of pear and banana essence.

CH3COOC8H17 - n-octyl acetate has an orange scent.

Esters of butyric acid

C3H7COOC2H5 - ethyl butyrate, bp = 121.5 ° C; has a characteristic pineapple smell.

C3H7COOC5H11 - n-amylbutyrate (n-pentylbutyrate) and C3H7COOCH2CH2CH (CH3) 2 - isoamylbutyrate (isopentylbutyrate) have a pear scent.

Esters of isovaleric acid

(CH3) 2CHCH2COOCH2CH2CH (CH3) 2 - isoamylisovalerate (isopentylisovalerate) has an apple smell.

4. Technical application of esters

Esters have great technical application... Due to their pleasant smell and harmlessness, they have long been used in confectionery, perfumery, and are widely used as plasticizers and solvents.

So, ethyl-, butyl - and amylacetates dissolve celluloid (nitrocellulose glues); dibutyl oxalate is a nitrocellulose plasticizer.

Glycerin acetates serve as cellulose acetate gellants and perfume fixatives. The esters of adipic and methyladipic acids find a similar application.

High molecular weight esters, for example, methyl oleate, butyl palmitate, isobutyl laurate, etc., are used in the textile industry for processing paper, woolen and silk fabrics, terpinyl acetate and cinnamic acid methyl ester - as insecticides.

5. Esters in perfumery

The following esters are used in perfumery and cosmetic production:

Linalyl acetate is a colorless transparent liquid with an odor reminiscent of bergamot oil. It is found in the oil of clary sage, lavender, bergamot, etc. It is used in the manufacture of compositions for perfumery and fragrances for cosmetics and soaps. The starting material for the production of linalyl acetate is any essential oil containing linalool (coriander and other oils). Linalyl acetate is obtained by acetylation of linalool with acetic anhydride. Linalyl acetate is purified from impurities by double distillation under vacuum.

Terpinyl acetate is produced by the interaction of terpineol with acetic anhydride in the presence of sulfuric acid. Perfume compositions and fragrances for soaps with a floral scent are prepared from it.

Diluted benzyl acetate has a jasmine-like scent. It is found in some essential oils and is the main constituent of oils extracted from jasmine, hyacinth, and gardenia flowers. In the production of synthetic fragrances, benzyl acetate is produced by the interaction of benzyl alcohol or benzyl chloride with acetic acid derivatives. It is used to prepare perfume compositions and fragrances for soap.

Methyl salicylate is a part of cassian, ylang-ylang and others essential oils... It is used industrially for the manufacture of compositions and fragrances for soap as a product with an intense odor, reminiscent of the smell of ylang-ylang. It is obtained by the interaction of salicylic acid and methyl alcohol in the presence of sulfuric acid.

6. The use of esters in the food industry

In the manufacture of milk and cream substitutes, confectionery, chewing gum, glaze and fillings - the recommended rate is up to 5 g / kg. Sorbitan monostearate is also added to dietary supplements. In the non-food industry, E491 is added in the manufacture of medicines, cosmetic products (creams, lotions, deodorants), for the production of emulsions for plant treatment.

Sorbitan Monostearate

Food additive E-491 of the group of stabilizers. It can be used as an emulsifier (for example, in instant yeast).

pharmaceutical ester soap

Characteristics: E491 is produced synthetically by direct esterification of sorbitol with stearic acid with the simultaneous formation of sorbitol anhydrides.

Application: E-491 is used as an emulsifier in the production of pastries, drinks, sauces in an amount of up to 5 g / kg. In the production of ice cream and liquid tea concentrates - up to 0.5 g / l. In the Russian Federation, sorbitan monostearate is also used as a consistency stabilizer, thickener, texturer, binding agent in liquid tea concentrates, fruit and herbal decoctions in amounts up to 500 mg / kg. In the manufacture of milk and cream substitutes, confectionery, chewing gum, glaze and fillings - the recommended rate is up to 5 g / kg. Sorbitan monostearate is also added to dietary supplements. In the non-food industry, E491 is added in the manufacture of medicines, cosmetic products (creams, lotions, deodorants), for the production of emulsions for plant treatment.

Effect on the human body: permissible daily rate- 25 mg / kg body weight. E491 is considered a low-hazard substance, does not cause danger when it comes into contact with the skin or gastric mucosa, and has a weak irritant effect on them. Excessive consumption of E491 can lead to fibrosis, growth retardation and enlargement of the liver.

Lecithin (E-322).

Feature: antioxidant. In industrial production, lecithin is obtained from production waste of soybean oil.

Application: as an emulsifier food supplement E-322 is used in the production of dairy products, margarine, bakery and chocolate products, as well as glazes. In the non-food industry, lecithin is used in the production of oil paints, solvents, vinyl coatings, cosmetics, as well as in the production of fertilizers, pesticides and paper processing.

Lecithin is found in foods that are high in fat. These are eggs, liver, peanuts, some types of vegetables and fruits. Also, a huge amount of lecithin is found in all cells of the human body.

Effect on the human body: lecithin is an essential substance for the human body. However, despite the fact that lecithin is very useful for humans, its use in large quantities can lead to undesirable consequences - the occurrence of allergic reactions.

Esters of glycerin and resin acids (E445)

They belong to the group of stabilizers and emulsifiers designed to maintain the viscosity and consistency of food products.

Application: glycerin esters are approved for use on the territory of the Russian Federation and are widely used in the food industry in the production of:

Marmalade, jam, jelly,

Fillers for fruit, sweets, chewing gums,

Low calorie foods,

Low-calorie oils,

Condensed cream and dairy products,

Ice cream,

Cheese and cheese products, puddings,

Jellied meat and fish products, and other products.

Impact on the human body: numerous studies have proven that the use of E-445 supplements can lead to a decrease in blood cholesterol and weight. Esters of resin acids can be allergens and irritate the skin. The additive E445 used as an emulsifier can irritate the mucous membranes of the body and upset the stomach. In production baby food glycerin esters are not used.

7. Esters in the pharmaceutical industry

Esters are components of cosmetic creams and medicinal ointments, as well as essential oils.

Nitroglycerin (Nitroglycerinum)

Cardiovascular Drug Nitroglycerin is an ester of nitric acid and a trihydric alcohol of glycerin, so it can be called glycerol trinitrate.

Get nitroglycerin by adding a mixture of nitric and sulfuric acids to the calculated amount of glycerin.

The resulting nitroglycerin is collected in the form of an oil above the acidic layer. It is separated, washed several times with water, diluted soda solution (to neutralize the acid) and then again with water. Thereafter, it is dried with anhydrous sodium sulfate.

The reaction for the formation of nitroglycerin can be schematically represented as follows:

Nitroglycerin is used in medicine as an antispasmodic (coronary dilator) agent for angina pectoris. The drug is available in bottles of 5-10 ml of a 1% alcohol solution and in tablets that contain 0.5 mg of pure nitroglycerin in each tablet. Store bottles with nitroglycerin solution in a cool place protected from light, away from fire. List B.

Acetylsalicylic acid (Aspirin, Acidum acetylsalicylicum)

White crystalline substance, slightly soluble in water, well soluble in alcohol, in alkali solutions. This substance is obtained by the interaction of salicylic acid with acetic anhydride:

Acetylsalicylic acid has been widely used as a drug for over 100 years - antipyretic, analgesic and anti-inflammatory.

Phenyl salicylate (salol, Phenylii salicylas)

Also known as salicylic acid phenyl ester (Figure 5).

Rice. 6 Scheme of obtaining phenyl salicylate.

Salol is an antiseptic, breaking down in the alkaline contents of the intestine, releasing salicylic acid and phenol. Salicylic acid has antipyretic and anti-inflammatory effects, phenol is active against pathogenic intestinal microflora. Has some uroantiseptic effect. Compared with modern antimicrobial drugs, phenyl salicylate is less active, but low toxic, does not irritate the gastric mucosa, does not cause dysbiosis and other complications of antimicrobial therapy.

Diphenhydramine (Diphenhydramine, Dimedrolum)

Another name: 2-dimethylaminoethyl ether of benzhydrol hydrochloride). Diphenhydramine is obtained by the interaction of benzhydrol and dimethylaminoethyl chloride hydrochloride in the presence of alkali. The base obtained is converted by the action of hydrochloric acid to the hydrochloride salt.

It has an antihistamine, antiallergic, antiemetic, hypnotic, local anesthetic effect.

Vitamins

Vitamin A palmitate (Retinyl palmitate) is an ester of retinol and palmitic acid. It is a regulator of keratinization processes. As a result of the use of products containing it, the density of the skin and its elasticity increase.

Vitamin B15 (pangamic acid) is an ester of gluconic acid and dimethylglycine. Participates in the biosynthesis of choline, methionine and creatine as a source of methyl groups. with circulatory disorders.

Vitamin E (tocopherol acetate) is a natural antioxidant that prevents the fragility of blood vessels. An irreplaceable fat-soluble component for the human body, it comes mainly in the composition of vegetable oils. Normalizes reproductive function; prevents the development of atherosclerosis, degenerative-dystrophic changes in the heart muscle and skeletal muscles.

Fats are mixtures of esters formed by the trihydric alcohol glycerol and higher fatty acids. General fat formula:

The common name for such compounds is triglycerides or triacylglycerols, where acyl is the carboxylic acid residue -C (O) R. The carboxylic acids in fats usually have a hydrocarbon chain with 9-19 carbon atoms.

Animal fats (cow oil, lamb, lard) are plastic low-melting substances. Vegetable fats (olive, cottonseed, sunflower oil) are viscous liquids. Animal fats mainly consist of a mixture of stearic and palmitic acid glycerides (Fig. 9A, 9B).

Vegetable oils contain glycerides of acids with a slightly shorter carbon chain: lauric C11H23COOH and myristic C13H27COOH. (like stearic and palmitic, these are saturated acids). Such oils can be stored in air for a long time without changing their consistency, and therefore are called non-drying. In contrast, linseed oil contains the glyceride of unsaturated linoleic acid (Figure 9B).

When applied in a thin layer to a surface, such oil dries out under the influence of atmospheric oxygen during polymerization along double bonds, thus forming an elastic film insoluble in water and organic solvents. Based linseed oil make natural drying oil. Animal and vegetable fats are also used in the manufacture of lubricants.

Rice. 9 (A, B, C)

9. Obtaining soap

Fats as esters are characterized by a reversible hydrolysis reaction catalyzed by mineral acids. With the participation of alkalis (or carbonates of alkali metals), the hydrolysis of fats occurs irreversibly. The products in this case are soaps - salts of higher carboxylic acids and alkali metals.

Sodium salts are solid soaps, potassium salts are liquid. The reaction of alkaline hydrolysis of fats, and in general all esters, is also called saponification.

Saponification of fats can also take place in the presence of sulfuric acid (acid saponification). This produces glycerin and higher carboxylic acids. Recent action alkali or soda is converted into soaps.

Vegetable oils (sunflower, cottonseed, etc.), animal fats, as well as sodium hydroxide or soda ash are the initial raw materials for soap production. Vegetable oils are pre-hydrogenated, i.e. they are converted into solid fats. Fat substitutes are also used - synthetic carboxylic fatty acids with a high molecular weight.

The production of soap requires large quantities of raw materials, therefore the task is to obtain soap from non-food products. The carboxylic acids necessary for the production of soap are obtained by the oxidation of paraffin. By neutralizing acids containing from 10 to 16 carbon atoms in the molecule, toilet soap is obtained, and from acids containing from 17 to 21 carbon atoms, - laundry soap and soap for technical purposes. Both synthetic soaps and soaps made from fats do not wash well in hard water. Therefore, along with soap from synthetic acids, detergents are produced from other types of raw materials, for example, from alkyl sulfates - salts of esters of higher alcohols and sulfuric acid.

10. Fats in cooking and pharmaceuticals

Salomas is a solid fat, a hydrogenation product of sunflower, peanut, coconut, palm kernel, soybean, cottonseed, as well as rapeseed oil and whale oil. Food salomas are used for the manufacture of margarine products, confectionery, bakery products.

In the pharmaceutical industry for the manufacture of drugs ( fish fat in capsules), as a basis for ointments, suppositories, creams, emulsions.

Conclusion

Esters are widely used in the technical, food and pharmaceutical industries. Products and products of these industries are widely used by humans in everyday life. A person encounters esters by eating certain foods and medicines using perfumes, clothing made from certain fabrics and some insecticides, soap and household chemicals.

Some representatives of this class of organic compounds are safe, others require limited use and caution in use.

In general, it can be concluded that esters are firmly established in many areas of human life.

List of sources used

1. Kartsova A.A. The conquest of matter. Organic chemistry: manual - SPb: Khimizdat, 1999 .-- 272 p.

2. Pustovalova L.M. Organic chemistry. - Rostov n / a: Phoenix, 2003 - 478 p.

3.http: //ru.wikipedia.org

4.http: //files.school-collection.edu.ru

5.http: //www.ngpedia.ru

6.http: //www.xumuk.ru

7.http: //www.ximicat.com

Posted on Allbest.ru

Esters in nature and technology

Esters are widespread in nature, find application in technology and various industries. They are good solvents for organic substances, their density is less than that of water, and they practically do not dissolve in it. Thus, esters with a relatively low molecular weight are flammable liquids with low boiling points and smells of various fruits. They are used as solvents for varnishes and paints, flavoring products in the food industry. For example, methyl ester of butyric acid has the smell of apples, ethyl alcohol of this acid has the smell of pineapples, isobutyl ester of acetic acid has the smell of bananas:
C 3 H 7 —COO — CH 3 (butyric acid methyl ester);
C 3 H 7 —COO — C 2 H 5 (butyric acid ethyl ester);
CH 3 -COO-CH 2 -CH 2 (acetic acid isobutyl ester)
Esters of higher carboxylic acids and higher monobasic alcohols are called waxes... So, beeswax consists mainly of palmitic acid ester of myricyl alcohol C 15 H 31 COOC 31 H 63; sperm whale wax - spermaceti - an ester of the same palmitic acid and cetyl alcohol C 15 H 31 COOC 16 H 33

The most important representatives of esters are fats.

Fats, oils

Fats- these are esters of glycerol and higher monoatomic. The common name for such compounds is triglycerides or triacylglycerols, where acyl is the carboxylic acid residue -C (O) R. Natural triglycerides contain residues of saturated acids (palmitic C 15 H 31 COOH, stearic C 17 H 35 COOH) and unsaturated (oleic C 17 H 33 COOH, linoleic C 17 H 31 COOH). Higher carboxylic acids that are part of fats always have an even number of carbon atoms (C 8 - C 18) and an unbranched hydrocarbon residue. Natural fats and oils are mixtures of higher carboxylic acid glycerides.

The composition and structure of fats can be reflected by the general formula:

Esterification- the reaction of the formation of esters.

The composition of fats can include residues of both saturated and unsaturated carboxylic acids in various combinations.

Under normal conditions, fats containing residues of unsaturated acids are most often liquid. They are called oils... Basically, these are fats of vegetable origin - linseed, hemp, sunflower and other oils (with the exception of palm and coconut oil- solid under normal conditions). Less common are liquid animal fats such as fish oil. Under normal conditions, most natural fats of animal origin are solid (low-melting) substances and contain mainly residues of saturated carboxylic acids, for example, mutton fat.
The composition of fats determines their physical and chemical properties.

Physical properties of fats

Fats are insoluble in water, do not have a clear melting point, and significantly increase in volume when melted.

The aggregate state of fats is solid, this is due to the fact that the composition of fats contains residues of saturated acids and fat molecules are capable of tight packing. The oils contain residues of unsaturated acids in cis - configuration, therefore, close packing of molecules is impossible, and the state of aggregation is liquid.

Chemical properties of fats

Fats (oils) are esters and are characterized by ester reactions.

It is clear that all reactions of unsaturated compounds are characteristic of fats containing residues of unsaturated carboxylic acids. They discolor bromine water and enter into other addition reactions. The most important reaction in practical terms is the hydrogenation of fats. Solid esters are obtained by hydrogenation of liquid fats. It is this reaction that underlies the production of margarine - solid fat from vegetable oils. Conventionally, this process can be described by the reaction equation:

All fats, like other esters, undergo hydrolysis:

Hydrolysis of esters is a reversible reaction. To in the direction of the formation of hydrolysis products, it is carried out in an alkaline medium (in the presence of alkalis or Na 2 CO 3). Under these conditions, the hydrolysis of fats is reversible, and leads to the formation of salts of carboxylic acids, which are called. fat in an alkaline environment is called saponification of fats.

When fats are saponified, glycerin and soaps are formed - sodium and potassium salts of higher carboxylic acids:

Saponification- alkaline hydrolysis of fats, obtaining soap.

Soap- mixtures of sodium (potassium) salts of higher saturated carboxylic acids (sodium soap - solid, potassium - liquid).

Soaps are surfactants (abbreviated: surfactants, detergents). The washing action of soap is due to the fact that the soaps emulsify fats. Soaps form micelles with pollutants (conventionally, these are fats with various inclusions).

The lipophilic part of the soap molecule dissolves in the contaminant, and the hydrophilic part ends up on the surface of the micelle. Micelles are charged with the same name, therefore they are repelled, while the pollutant and water turns into an emulsion (practically it is dirty water).

Soap also occurs in the water, creating an alkaline environment.

Soaps cannot be used in harsh and sea water, since the resulting calcium (magnesium) stearates are insoluble in water.

Introduction -3-

1. Structure -4-

2. Nomenclature and isomerism -6-

3. Physical properties and being in nature -7-

4. Chemical properties -8-

5. Getting -9-

6. Application -10-

6.1 Use of inorganic acid esters -10-

6.2 Use of organic acid esters -12-

Conclusion -14-

Used sources of information -15-

Appendix -16-

Introduction

Among the functional derivatives of acids, esters, derivatives of acids, in which the acidic hydrogen is replaced by alkyl (or generally hydrocarbon) radicals, occupy a special place.

Esters are classified according to which acid they are derived from (inorganic or carboxylic).

Among the esters, a special place is occupied by natural esters - fats and oils, which are formed by the trihydric alcohol glycerol and higher fatty acids containing an even number of carbon atoms. Fats are part of plant and animal organisms and serve as one of the energy sources of living organisms, which is released during the oxidation of fats.

The purpose of my work is to familiarize yourself in detail with such a class of organic compounds as esters and in-depth consideration of the field of application of individual representatives of this class.

1. Structure

General formula of carboxylic acid esters:

where R and R "are hydrocarbon radicals (in esters of formic acid, R is a hydrogen atom).

General fat formula:

where R ", R", R "" are carbon radicals.

Fats can be “simple” and “mixed”. The composition of simple fats contains the remains of the same acids (ie, R '= R "= R" "), the composition of mixed fats contains different ones.

The following fatty acids are most commonly found in fats:

Alkanoic acids

1. Butyric acid CH 3 - (CH 2) 2 - COOH

3. Palmitic acid CH 3 - (CH 2) 14 - COOH

4. Stearic acid CH 3 - (CH 2) 16 - COOH

Alkenic acids

5. Oleic acid C 17 H 33 COOH

CH 3 - (CH 2) 7 -CH === CH- (CH 2) 7 -COOH

Alkadienic acids

6. Linoleic acid C 17 H 31 COOH

CH 3 - (CH 2) 4 -CH = CH-CH 2 -CH = CH-COOH

Alcatrienoic acids

7. Linolenic acid C 17 H 29 COOH

CH 3 CH 2 CH = CHCH 2 CH == CHCH 2 CH = CH (CH 2) 4 COOH

2. Nomenclature and isomerism

Ester names are derived from the name of the hydrocarbon radical and the name of the acid, in which the suffix is used instead of the ending -ova - at , for example:

The following types of isomerism are characteristic of esters:

1. The isomerism of the carbon chain begins at the acid residue with butanoic acid, and at the alcohol residue with propyl alcohol, for example, ethyl butyrate is isomeric with ethyl isobutyrate, propyl acetate and isopropyl acetate.

2. Isomerism of the position of the ester group -CO-O-. This type of isomerism begins with esters that contain at least 4 carbon atoms, such as ethyl acetate and methyl propionate.

3. Interclass isomerism, e.g. isomeric propanoic acid methyl acetate.

For esters containing unsaturated acid or unsaturated alcohol, two more types of isomerism are possible: isomerism of the position of the multiple bond and cis-, trans-isomerism.

3. Physical properties and being in nature

Esters of lower carboxylic acids and alcohols are volatile, water-insoluble liquids. Many of them have a pleasant smell. So, for example, butyl butyrate has a pineapple smell, isoamyl acetate - pears, etc.

Esters of higher fatty acids and alcohols are waxy substances, odorless, insoluble in water.

The pleasant aroma of flowers, fruits, berries is largely due to the presence of certain esters in them.

Fats are widespread in nature. Along with hydrocarbons and proteins, they are part of all plant and animal organisms and constitute one of the main parts of our food.

By aggregate state at room temperature, fats are divided into liquid and solid. Hard fats, as a rule, are formed by saturated acids, liquid fats (they are often called oils) - unsaturated ones. Fats are soluble in organic solvents and insoluble in water.

4. Chemical properties

1. Reaction of hydrolysis, or saponification. Since the esterification reaction is reversible, the reverse hydrolysis reaction takes place in the presence of acids:

The hydrolysis reaction is also catalyzed by alkalis; in this case, hydrolysis is irreversible, since the resulting acid forms a salt with alkali:

2. Reaction of addition. Esters containing unsaturated acid or alcohol are capable of addition reactions.

3. Recovery reaction. The reduction of esters with hydrogen leads to the formation of two alcohols:

4. Reaction of amide formation. Under the action of ammonia, esters are converted to acid amides and alcohols:

5. Receiving

1. The reaction of esterification:

Alcohols react with mineral and organic acids to form esters. The reaction is reversible (reverse process - hydrolysis of esters).

The reactivity of monohydric alcohols in these reactions decreases from primary to tertiary.

2. Interaction of acid anhydrides with alcohols:

3. Interaction of acid halides with alcohols:

6. Application

6.1 Use of inorganic acid esters

Boric acid esters - trialkylborates- easily obtained by heating alcohol and boric acid with the addition of concentrated sulfuric acid. Boronomethyl ether (trimethyl borate) boils at 65 ° C, boron ethyl (triethyl borate) - at 119 ° C. Esters of boric acid are easily hydrolyzed with water.

The reaction with boric acid serves to establish the configuration of polyhydric alcohols and has been repeatedly used in the study of sugars.

Orthosilicon ethers- liquids. Methyl ether boils at 122 ° С, ethyl ether at 156 ° С.Hydrolysis with water proceeds easily even in the cold, but it proceeds gradually and with a lack of water leads to the formation of high molecular weight anhydride forms in which silicon atoms are connected to each other through oxygen (siloxane groups) :

These high molecular weight substances (polyalkoxysiloxanes) are used as binders that can withstand rather high temperatures, in particular for coating the surface of molds for precision metal casting.

Dialkyl dichlorosilanes react similarly to SiCl 4, for example ((CH 3) 2 SiCl 2, forming dialkoxy derivatives:

Their hydrolysis with a lack of water gives the so-called polyalkylsiloxanes:

They have different (but very significant) molecular weights and are viscous liquids used as heat-resistant lubricants, and with even longer siloxane skeletons - heat-resistant electrical insulating resins and rubbers.

Orthotitanic acid esters. Their get similarly to orthosilicon ethers by the reaction:

These liquids, easily hydrolyzed to methyl alcohol and TiO 2, are used to impregnate fabrics in order to make them waterproof.

Esters of nitric acid. They are obtained by the action of a mixture of nitric and concentrated sulfuric acids on alcohols. Methyl nitrate CH 3 ONO 2 (bp 60 ° C) and ethyl nitrate C 2 H 5 ONO 2 (bp 87 ° C) can be distilled with careful work, but when heated above the boiling point or during detonation they are very strong blow up.

Ethylene glycol and glycerin nitrates, incorrectly called nitroglycol and nitroglycerin, are used as explosives. Nitroglycerin itself (a heavy liquid) is inconvenient and dangerous to handle.

Pentrite - tetranitrate of pentaerythritol C (CH 2 ONO 2) 4, obtained by treating pentaerythritol with a mixture of nitric and sulfuric acids, is also a strong explosive with blasting action.

Glycerin nitrate and pentaerythritol nitrate have a vasodilating effect and are used as symptomatic agents for angina pectoris.

Methods for preparing esters

The most important way to obtain esters is the esterification reaction - acid + alcohol.

Using the method of labeled atoms, it was proved that during esterification, hydroxyl is removed from the acid molecule, and hydrogen from the alcohol molecule.

Chemical properties of esters

1. The reaction of esterification

The main chemical property is the hydrolysis of esters - the splitting of esters by the action of water. This reaction is the reverse of the esterification reaction. The reaction proceeds both in an acidic (reaction catalysts - H + protons) and in an alkaline medium (reaction catalysts - OH - hydroxide ions).

In the presence of alkali, the reaction is irreversible, because saponification occurs - the formation of salts of carboxylic acids.

In solutions of dilute mineral acids, salts of carboxylic acids are again converted to the original carboxylic acid:

2СН 3 СООNa + H 2 SO 4 dil. → 2CH 3 COOH + Na 2 SO 4

sodium acetate acetic acid

2. Recovery reaction

When esters are reduced, a mixture of two alcohols is formed:

3. Interaction with ammonia

When esters react with ammonia, amides are formed:

The use of esters

Many esters have a pleasant scent. So, the amyl ester of formic acid has a cherry smell, isoamyl ester of acetic acid - the smell of pears. These esters are used to make artificial essences used in the production of fruit waters, etc., as well as in perfumery.

Ethyl acetate is used as a solvent and in the manufacture of medicines.