Where are esters used? Esters: chemical properties and applications. The most common esters and their areas of application

Methods for producing esters

The most important method for producing esters is the esterification reaction - acid + alcohol.

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

Chemical properties of esters

1. Esterification reaction

The main chemical property is ester hydrolysis - the breakdown of esters under the influence of water. This reaction is the reverse of the esterification reaction. The reaction occurs both in an acidic environment (reaction catalysts are H + protons) and in an alkaline environment (reaction catalysts are hydroxide ions OH –).

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 converted back into the original carboxylic acid:

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

sodium acate 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:

Application of esters

Many esters have a pleasant odor. Thus, amyl ester of formic acid has the smell of cherries, isoamyl ester of acetic acid has the smell of pears. These esters are used to make artificial essences used in the production of fruit waters, etc., as well as in perfumes.

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

10.5. Esters. Fats

Esters– functional derivatives of carboxylic acids,
in molecules in which the hydroxyl group (-OH) is replaced by an alcohol residue (- OR)

Esters of carboxylic acids – compounds with a general formula.

R-COOR", where R and R" are hydrocarbon radicals.

Esters of saturated monobasic carboxylic acids have a general formula:

Physical properties:

· Volatile, colorless liquids

· Poorly soluble in water

· Most often with a pleasant smell

Lighter than water

Esters are found in flowers, fruits, and berries. They determine their specific smell.
They are a component of essential oils (about 3000 e.m. are known - orange, lavender, rose, etc.)

Esters of lower carboxylic acids and lower monohydric alcohols have a pleasant smell of flowers, berries and fruits. Esters of higher monobasic acids and higher monohydric alcohols are the basis of natural waxes. For example, beeswax contains an ester of palmitic acid and myricyl alcohol (myricyl palmitate):

CH 3 (CH 2) 14 –CO–O–(CH 2) 29 CH 3

Aroma.

Structural formula.

Ester name

Apple

Ethyl ether

2-methylbutanoic acid

Cherry

Amyl formic acid ester

Pear

Isoamyl ester of acetic acid

A pineapple

Butyric acid ethyl ester

(ethyl butyrate)

Banana

Isobutyl ester of acetic acid

(isoamyl acetate also has a banana smell)

Jasmine

Benzyl ether acetate (benzyl acetate)

The short names of esters are based on the name of the radical (R") in the alcohol residue and the name of the RCOO group in the acid residue. For example, ethyl ether acetic acid CH 3 COO C 2 H 5 called ethyl acetate.

Application

· As fragrances and odor enhancers in the food and perfumery (production of soap, perfume, creams) industries;

· In the production of plastics and rubber as plasticizers.

Plasticizers – substances that are introduced into the composition of polymer materials to impart (or increase) elasticity and (or) plasticity during processing and operation.

Application in medicine

IN late XIX- at the beginning of the twentieth century, when organic synthesis took its first steps, many esters were synthesized and tested by pharmacologists. They became the basis of such medicines as salol, validol, etc. Methyl salicylate was widely used as a local irritant and analgesic, which has now been practically replaced by more effective drugs.

Preparation of esters

Esters can be obtained by reacting carboxylic acids with alcohols ( esterification reaction). The catalysts are mineral acids.

The esterification reaction under acid catalysis is reversible. The reverse process - the cleavage of an ester under the action of water to form a carboxylic acid and alcohol - is called ester hydrolysis.

RCOOR " + H2O ( H +) ↔ RCOOH + R "OH

Hydrolysis in the presence of alkali is irreversible (since the resulting negatively charged carboxylate anion RCOO does not react with the nucleophilic reagent - alcohol).

This reaction is called saponification of esters(by analogy with alkaline hydrolysis of ester bonds in fats when producing soap).

Fats, their structure, properties and applications

“Chemistry is everywhere, chemistry is in everything:

In everything we breathe

In everything we drink

In everything we eat."

In everything we wear

People have long learned to extract fat from natural objects and use it in Everyday life. Fat burned in primitive lamps, illuminating the caves primitive people, grease was used to lubricate the runners on which ships were launched. Fats are the main source of our nutrition. But poor nutrition and a sedentary lifestyle lead to excess weight. Desert animals store fat as a source of energy and water. The thick fat layer of seals and whales helps them swim in the cold waters of the Arctic Ocean.

Fats are widely distributed in nature. Along with carbohydrates and proteins, they are part of all animal and plant organisms and constitute one of the main parts of our food. Sources of fats are living organisms. Animals include cows, pigs, sheep, chickens, seals, whales, geese, fish (sharks, cod, herring). Fish oil, a medicinal product, is obtained from the liver of cod and shark, and fats used to feed farm animals are obtained from herring. Vegetable fats are most often liquid and are called oils. Fats from plants such as cotton, flax, soybeans, peanuts, sesame, rapeseed, sunflower, mustard, corn, poppy, hemp, coconut, sea buckthorn, rose hips, oil palm and many others are used.

Fats perform various functions: construction, energy (1 g of fat provides 9 kcal of energy), protective, storage. Fats provide 50% of the energy required by a person, so a person needs to consume 70–80 grams of fat per day. Fats make up 10–20% of body weight healthy person. Fats are an essential source of fatty acids. Some fats contain vitamins A, D, E, K, and hormones.

Many animals and humans use fat as a heat-insulating shell; for example, in some marine animals the thickness of the fat layer reaches a meter. In addition, fats are solvents for flavoring agents and dyes in the body. Many vitamins, such as vitamin A, are only fat soluble.

Some animals (usually waterfowl) use fats to lubricate their own muscle fibers.

Fats increase the satiety effect of foods because they are digested very slowly and delay the onset of hunger. .

History of the discovery of fats

Back in the 17th century. German scientist, one of the first analytical chemists Otto Tacheny(1652–1699) first suggested that fats contained a “hidden acid.”

In 1741 French chemist Claude Joseph Geoffroy(1685–1752) discovered that when soap (which was prepared by boiling fat with alkali) decomposes with acid, a mass is formed that is greasy to the touch.

The fact that fats and oils contain glycerin was first discovered in 1779 by the famous Swedish chemist Karl Wilhelm Scheele.

The chemical composition of fats was first determined by a French chemist at the beginning of the last century. Michel Eugene Chevreul, the founder of the chemistry of fats, the author of numerous studies of their nature, summarized in the six-volume monograph “Chemical Studies of Bodies of Animal Origin.”

1813 E. Chevreul established the structure of fats, thanks to the hydrolysis reaction of fats in an alkaline environment. He showed that fats consist of glycerol and fatty acids, and this is not just a mixture of them, but a compound that, by adding water, breaks down into glycerol and acids.

Fat synthesis

In 1854, the French chemist Marcelin Berthelot (1827–1907) carried out an esterification reaction, that is, the formation of an ester between glycerol and fatty acids, and thus synthesized fat for the first time.

General formula of fats (triglycerides)

Fats – esters of glycerol and higher carboxylic acids. The common name for these compounds is triglycerides.

Classification of fats

Animal fats contain mainly glycerides of saturated acids and are solids. Vegetable fats, often called oils, contain glycerides of unsaturated carboxylic acids. These are, for example, liquid sunflower, hemp and linseed oils.

Natural fats contain the following fatty acids

Saturated:

stearic (C 17 H 35 COOH)

palmitic (C 15 H 31 COOH)

Oily (C 3 H 7 COOH)

CONTAINING

ANIMALS

FATS

Unsaturated :

oleic (C 17 H 33 COOH, 1 double bond)

linoleic (C 17 H 31 COOH, 2 double bonds)

linolenic (C 17 H 29 COOH, 3 double bonds)

arachidonic (C 19 H 31 COOH, 4 double bonds, less common)

CONTAINING

PLANT

FATS

Fats are found in all plants and animals. They are mixtures of full glycerol esters and do not have a clearly defined melting point.

· Animal fats(lamb, pork, beef, etc.), as a rule, are solid substances with a low melting point (an exception is fish oil). Residues predominate in solid fats saturated acids

· Vegetable fats - oils (sunflower, soybean, cottonseed, etc.) – liquids (exception – coconut oil, cocoa bean butter). Oils contain mainly residues unsaturated (unsaturated) acids

Chemical properties of fats

1. Hydrolysis, or saponification , fat occurs under the influence of water, with the participation of enzymes or acid catalysts (reversible), in this case, alcohol - glycerin and a mixture of carboxylic acids are formed:

or alkalis (irreversible). Alkaline hydrolysis produces salts of higher fatty acids, called soaps. Soaps are obtained by hydrolysis of fats in the presence of alkalis:

Soaps are potassium and sodium salts of higher carboxylic acids.

2. Hydrogenation of fats – conversion of liquid vegetable oils into solid fats - has great importance for food purposes. The product of oil hydrogenation is solid fat (artificial lard, salomas). Margarine– edible fat, consists of a mixture of hydrogenated oils (sunflower, corn, cottonseed, etc.), animal fats, milk and flavoring additives (salt, sugar, vitamins, etc.).

This is how margarine is produced in industry:

Under the conditions of the oil hydrogenation process (high temperature, metal catalyst), some of the acid residues containing cis C=C bonds are isomerized into more stable trans isomers. An increased content of trans-unsaturated acid residues in margarine (especially in cheap varieties) increases the risk of atherosclerosis, cardiovascular and other diseases.

Fat production reaction (esterification)

Application of fats

Fats are a food product. Biological role fat

Animal fats and vegetable oils, along with proteins and carbohydrates, are one of the main components of normal human nutrition. They are the main source of energy: 1 g fat per complete oxidation(it goes into cells with the participation of oxygen) provides 9.5 kcal (about 40 kJ) of energy, which is almost twice as much as can be obtained from proteins or carbohydrates. In addition, fat reserves in the body contain practically no water, while protein and carbohydrate molecules are always surrounded by water molecules. As a result, one gram of fat provides almost 6 times more energy than one gram of animal starch - glycogen. Thus, fat should rightfully be considered a high-calorie “fuel”. It is mainly spent to maintain the normal temperature of the human body, as well as to work various muscles, so even when a person is doing nothing (for example, sleeping), he needs about 350 kJ of energy every hour to cover energy costs, approximately the same power as an electric 100 -watt light bulb.

To provide the body with energy in unfavorable conditions, fat reserves are created in it, which are deposited in the subcutaneous tissue, in the fatty fold of the peritoneum - the so-called omentum. Subcutaneous fat protects the body from hypothermia (this function of fat is especially important for marine animals). For thousands of years, people have performed hard physical work, which required large amounts of energy and, accordingly, increased nutrition. To cover a person's minimum daily energy requirement, only 50 g of fat is enough. However, with moderate physical activity, an adult should receive slightly more fat from food, but their amount should not exceed 100 g (this provides a third of the calorie content for a diet of about 3000 kcal). It should be noted that half of these 100 g are contained in food in the form of so-called hidden fat. Fats are found in almost all foods: not large quantities they are even found in potatoes (0.4% of them), in bread (1-2%), in oatmeal (6%). Milk usually contains 2-3% fat (but there are also special varieties of skim milk). There is quite a lot of hidden fat in lean meat - from 2 to 33%. Hidden fat is present in the product in the form of individual tiny particles. Almost pure fats are lard and vegetable oil; Butter contains about 80% fat, and ghee – 98%. Of course, all the given recommendations for fat consumption are averages; they depend on gender and age, physical activity and climatic conditions. With excessive consumption of fats, a person quickly gains weight, but we should not forget that fats in the body can also be synthesized from other foods. “Working off” extra calories through physical activity is not so easy. For example, after jogging 7 km, a person spends approximately the same amount of energy as he gets by eating just one hundred gram chocolate bar (35% fat, 55% carbohydrates). Physiologists have found that with physical activity that is 10 times higher than usual, the person receiving the fat diet was completely exhausted after 1.5 hours. With a carbohydrate diet, a person withstood the same load for 4 hours. This seemingly paradoxical result is explained by the peculiarities of biochemical processes. Despite the high “energy intensity” of fats, obtaining energy from them in the body is a slow process. This is due to the low reactivity of fats, especially their hydrocarbon chains. Carbohydrates, although they provide less energy than fats, “release” it much faster. Therefore, before physical activity, it is preferable to eat sweets rather than fatty foods. An excess of fats in food, especially animals, increases the risk of developing diseases such as atherosclerosis, heart failure, etc. Animal fats contain a lot of cholesterol (but we should not forget that two-thirds of cholesterol is synthesized in the body from low-fat foods - carbohydrates and proteins).

It is known that a significant proportion of the fat consumed should be vegetable oils, which contain compounds that are very important for the body - polyunsaturated fatty acids with several double bonds. These acids are called “essential”. Like vitamins, they must enter the body in ready-made form. Of these, arachidonic acid has the greatest activity (it is synthesized in the body from linoleic acid), and linolenic acid has the least activity (10 times lower than linoleic acid). According to various estimates, a person’s daily need for linoleic acid ranges from 4 to 10 g. The highest amount of linoleic acid (up to 84%) is in safflower oil, squeezed from the seeds of safflower, an annual plant with bright orange flowers. There is also a lot of this acid in sunflower and nut oils.

According to nutritionists, a balanced diet should contain 10% polyunsaturated acids, 60% monounsaturated acids (mainly oleic acid) and 30% saturated acids. This is the ratio that is ensured if a person receives a third of fats in the form of liquid vegetable oils - in the amount of 30–35 g per day. These oils are also included in margarine, which contains from 15 to 22% saturated fatty acids, from 27 to 49% unsaturated and from 30 to 54% polyunsaturated. For comparison: butter contains 45–50% saturated fatty acids, 22–27% unsaturated and less than 1% polyunsaturated. In this regard, high-quality margarine is healthier than butter.

Must remember!!!

Saturated fatty acids negatively affect fat metabolism, liver function and contribute to the development of atherosclerosis. Unsaturated acids (especially linoleic and arachidonic acids) regulate fat metabolism and participate in the removal of cholesterol from the body. The higher the content of unsaturated fatty acids, the lower the melting point of fat. The calorie content of solid animal fats and liquid vegetable fats is approximately the same, but the physiological value of vegetable fats is much higher. Milk fat has more valuable qualities. It contains one third of unsaturated fatty acids and, preserved in the form of an emulsion, is easily absorbed by the body. Despite these positive traits, you should not consume only milk fat, since no fat contains the ideal composition of fatty acids. It is best to consume fats of both animal and plant origin. Their ratio should be 1:2.3 (70% animal and 30% plant) for young people and middle-aged people. Vegetable fats should predominate in the diet of older people.

Fats not only participate in metabolic processes, but are also stored in reserve (mainly in the abdominal wall and around the kidneys). Fat reserves provide metabolic processes, preserving proteins for life. This fat provides energy during physical activity, if little fat is supplied with food, as well as during severe illnesses, when due to decreased appetite, it is not supplied enough with food.

Excessive consumption of fat in food is harmful to health: it is stored in large quantities in reserve, which increases body weight, sometimes leading to disfigurement of the figure. Its concentration in the blood increases, which, as a risk factor, contributes to the development of atherosclerosis, coronary heart disease, hypertension, etc.

EXERCISES

1. There are 148 g of a mixture of two organic compounds of the same composition: C 3 H 6 O 2. Determine the structure of these soybeans dyenium and their mass fractions in the mixture, if it is known that one of when interacting with excess sodium bicarbonate, they release 22.4 l (n.s.) of carbon monoxide ( IV), and the other does not react with sodium carbonate and ammonia solution silver oxide, but when heated with aqueous solution sodium hydroxide forms an alcohol and an acid salt.

Solution:

It is known that carbon monoxide ( IV ) is released when sodium carbonate reacts with an acid. There can be only one acid of the composition C 3 H 6 O 2 - propionic, CH 3 CH 2 COOH.

C 2 H 5 COOH + N aHCO 3 → C 2 H 5 COONa + CO 2 + H 2 O.

According to the condition, 22.4 liters of CO 2 were released, which is 1 mol, which means there was also 1 mol of acid in the mixture. The molar mass of the starting organic compounds is: M (C 3 H 6 O 2) = 74 g/mol, therefore 148 g is 2 mol.

The second compound upon hydrolysis forms an alcohol and an acid salt, which means it is an ester:

RCOOR‘ + NaOH → RCOONa + R‘OH.

The composition C 3 H 6 O 2 corresponds to two esters: ethyl formate HCOOC 2 H 5 and methyl acetate CH 3 COOCH 3. Esters of formic acid react with an ammonia solution of silver oxide, so the first ester does not satisfy the conditions of the problem. Therefore, the second substance in the mixture is methyl acetate.

Since the mixture contained one mole of compounds with the same molar mass, their mass fractions are equal and amount to 50%.

Answer. 50% CH 3 CH 2 COOH, 50% CH 3 COOCH 3.

2. The relative density of ester vapor with respect to hydrogen is 44. During the hydrolysis of this ester, two compounds are formed, upon combustion of equal quantities of which equal volumes are formed carbon dioxide(under the same conditions). Give the structural formula of this ether.

Solution:

The general formula of esters formed by saturated alcohols and acids is C n N 2 n O 2. The value of n can be determined from the hydrogen density:

M (C n H 2 n O 2) = 14 n + 32 = 44. 2 = 88 g/mol,

whence n = 4, that is, ether contains 4 carbon atoms. Since the combustion of alcohol and acid formed during the hydrolysis of ether releases equal volumes of carbon dioxide, the acid and alcohol contain same number carbon atoms, two each. Thus, the desired ester is formed by acetic acid and ethanol and is called ethyl acetate:



CH 3 -		O-S 2 N 5

Answer. Ethyl acetate, CH 3 SOOC 2 H 5.

________________________________________________________________

3. During ester hydrolysis, molar mass which is 130 g/mol, acid A and alcohol B are formed. Determine the structure of the ester if it is known that the silver salt of the acid contains 59.66% silver by mass. Alcohol B is not oxidized by sodium dichromate and easily reacts with hydrochloric acid to form alkyl chloride.

Solution:

An ester has the general formula RCOOR ‘. It is known that the silver salt of the acid, RCOOAg , contains 59.66% silver, therefore the molar mass of salt is: M (RCOOAg) = M (A g )/0.5966 = 181 g/mol, from where M(R ) = 181-(12+2. 16+108) = 29 g/mol. This radical is ethyl, C 2 H 5, and the ester was formed by propionic acid: C 2 H 5 COOR '.

The molar mass of the second radical is: M (R ') = M (C 2 H 5 COOR ‘) - M(C 2 H 5 COO) = 130-73 = 57 g/mol. This radical has molecular formula C 4 H 9 . According to the condition, alcohol C 4 H 9 OH does not oxidize Na 2 C r 2 O 7 and reacts easily with HCl therefore, this alcohol is tertiary, (CH 3) 3 SON.

Thus, the desired ester is formed by propionic acid and tert-butanol and is called tert-butylpropionate:

		CH 3

C 2 H 5 -	C—O—	C - CH 3

		CH 3

Answer . Tert-butyl propionate.

________________________________________________________________

4. Write two possible formulas fat, which has 57 carbon atoms in its molecule and reacts with iodine in a ratio of 1:2. Fat contains acid residues with an even number of carbon atoms.

Solution:

General formula of fats:

where R, R’, R "—hydrocarbon radicals containing odd number carbon atoms (another atom from the acid residue is part of the -CO- group). Three hydrocarbon radicals account for 57-6 = 51 carbon atoms. It can be assumed that each of the radicals contains 17 carbon atoms.

Since one fat molecule can attach two iodine molecules, there are two double bonds or one triple bond per three radicals. If two double bonds are in one radical, then the fat contains a linoleic acid residue ( R = C 17 H 31) and two stearic acid residues ( R' = R " = C 17 H 35). If two double bonds are in different radicals, then the fat contains two oleic acid residues ( R = R ‘ = C 17 H 33 ) and a stearic acid residue ( R " = C 17 H 35). Possible fat formulas:

CH 2 - O - CO - C 17 H 31

CH - O - CO - C 17 H 35

CH 2 - O - CO - C 17 H 35

CH 2 - O - CO - C 17 H 33

CH - O - CO - C 17 H 35

CH - O - CO - C 17 H 33

________________________________________________________________

TASKS FOR INDEPENDENT SOLUTION

1. What is an esterification reaction?

2. What difference exists in the structure of solid and liquid fats?

3. What are Chemical properties fat

4. Give the reaction equation for the production of methyl formate.

5. Write the structural formulas of two esters and an acid having the composition C 3 H 6 O 2. Name these substances according to the international nomenclature.

6. Write the equations for the esterification reactions between: a) acetic acid and 3-methylbutanol-1; b) butyric acid and propanol-1. Name the ethers.

7. How many grams of fat were taken if 13.44 liters of hydrogen (N.S.) were required to hydrogenate the acid formed as a result of its hydrolysis?

8. Calculate the mass fraction of the yield of the ester formed when 32 g of acetic acid and 50 g of 2-propanol are heated in the presence of concentrated sulfuric acid, if 24 g of ester are formed.

9. To hydrolyze a fat sample weighing 221 g, 150 g of sodium hydroxide solution with mass fraction alkali 0.2. Propose the structural formula of the original fat.

10. Calculate the volume of a solution of potassium hydroxide with a mass fraction of alkali of 0.25 and a density of 1.23 g/cm 3 that must be consumed to carry out the hydrolysis of 15 g of a mixture consisting of ethanoic acid ethyl ester, methanoic acid propyl ester and propanoic acid methyl ester.

VIDEO EXPERIENCE

1. What reaction underlies the production of esters:
a) neutralization	b) polymerization
c) esterification	d) hydrogenation
2. How many isomeric esters correspond to the formula C 4 H 8 O 2:
a) 2

Esters– functional derivatives of carboxylic acids,
in molecules in which the hydroxyl group (-OH) is replaced by an alcohol residue (-OR)

Esters of carboxylic acids – compounds with the general formula

R-COOR",where R and R" are hydrocarbon radicals.

Esters of saturated monobasic carboxylic acids have a general formula:

Physical properties:

Volatile, colorless liquids

· Poorly soluble in water

· Most often with a pleasant smell

Lighter than water

Esters are found in flowers, fruits, and berries. They determine their specific smell.
They are a component of essential oils (about 3000 e.m. are known - orange, lavender, rose, etc.)

CH 3 (CH 2) 14 –CO–O–(CH 2) 29 CH 3

*Aroma.* *Structural formula.*	*Ester name*
*Apple*	Ethyl ether 2-methylbutanoic acid
*Cherry*	Amyl formic acid ester
*Pear*	Isoamyl ester of acetic acid
*A pineapple*	Butyric acid ethyl ester (ethyl butyrate)
*Banana*	Isobutyl ester of acetic acid (y isoamyl acetate also resembles the smell of banana)
*Jasmine*	Benzyl ether acetate (benzyl acetate)

The short names of esters are based on the name of the radical (R") in the alcohol residue and the name of the RCOO group in the acid residue. For example, ethyl acetic acid CH 3 COO C 2 H 5 called ethyl acetate.

Application

· As fragrances and odor enhancers in the food and perfumery (production of soap, perfume, creams) industries;

· In the production of plastics and rubber as plasticizers.

Plasticizers – substances that are introduced into the composition of polymer materials to impart (or increase) elasticity and (or) plasticity during processing and operation.

Application in medicine

At the end of the 19th and beginning of the 20th centuries, when organic synthesis took its first steps, many esters were synthesized and tested by pharmacologists. They became the basis of such medicines as salol, validol, etc. Methyl salicylate was widely used as a local irritant and analgesic, which has now been practically replaced by more effective drugs.

Preparation of esters

Esters can be obtained by reacting carboxylic acids with alcohols ( esterification reaction). The catalysts are mineral acids.

Video “Preparation of ethyl acetyl ether”

Video “Preparation of boronethyl ether”

RCOOR" + H2O (H+)↔ RCOOH + R"OH

Hydrolysis in the presence of alkali is irreversible (since the resulting negatively charged carboxylate anion RCOO does not react with the nucleophilic reagent - alcohol).

This reaction is called saponification of esters(by analogy with alkaline hydrolysis of ester bonds in fats when producing soap).

However, it is worth noting that their use has a huge positive effect on the human body, and is necessary for consumption in the same way as carbohydrates and proteins.

What are these esters?

Esters, or esters as they are also called, are derivatives of oxoacids (carbon, and also not organic compounds) which have a general formula, and, in fact, are products that interchange the hydrogen atoms of hydroxyls - OH with an acidic function with a hydrocarbon residue (aliphatic, alkenyl, aromatic or heteroaromatic), they are also considered as acyl derivatives of alcohols.

The most common esters and their areas of application

Acetates are esters of acetic acid that are used as solvents.
Lactates are lactic acids and have organic uses.
Butyrates are oily and also have organic uses.
Formates are formic acid, but due to their high toxin capacity, they are not particularly used.
It is also worth mentioning solvents based on isobutyl alcohol, as well as synthetic fatty acids, and alkylene carbonates.
Methyl acetate - it is produced as a wood alcohol solution. During the production of polyvinyl alcohol, it is formed as an additional product. Due to its ability to dissolve, it is used as a substitute for acetone, but has higher toxic properties.
Ethyl acetate - this ester is formed using the esterification method at forest chemical enterprises, during the processing of synthetic and forest chemical acetic acid. You can also get ethyl acetate based on methyl alcohol. Ethyl acetate has the ability to dissolve most polymers, like acetone. If necessary, you can purchase Ethyl Acetate in Kazakhstan. His abilities are great. Thus, its advantage over acetone is that it has a fairly high boiling point and lower volatility. It's worth adding 15-20% ethyl alcohol and the ability to dissolve increases.
Propyl acetate has similar dissolving properties to ethyl acetate.
Amyl acetate - its aroma resembles the smell of banana oil. Area of application - varnish solvent, because it dissolves slowly.
Esters with fruit aroma.
Vinyl acetate - applications include the preparation of adhesives, paints and resins.
Sodium and potassium salts form soaps.

Having examined and studied a little the advantages and scope of use of esters, you understand that they are a huge necessity in human life. Contribute to development in many areas of activity.

Esters are commonly called compounds obtained by esterification reaction from carboxylic acids. In this case, the OH- from the carboxyl group is replaced by an alkoxy radical. As a result, esters are formed, the formula of which is general view written as R-COO-R".

Structure of the ester group

Polarity chemical bonds in ester molecules is similar to the polarity of bonds in carboxylic acids. The main difference is the absence of a mobile hydrogen atom, in place of which a hydrocarbon residue is located. At the same time, the electrophilic center is located on the carbon atom of the ester group. But the carbon atom of the alkyl group connected to it is also positively polarized.

Electrophilicity, and therefore the chemical properties of esters, are determined by the structure of the hydrocarbon residue that takes the place of the H atom in the carboxyl group. If a hydrocarbon radical forms a conjugated system with an oxygen atom, then the reactivity increases noticeably. This happens, for example, in acrylic and vinyl esters.

Physical properties

Most esters are liquids or crystalline substances with a pleasant aroma. Their boiling point is usually lower than that of similar values molecular weights carboxylic acids. This confirms the decrease in intermolecular interactions, and this, in turn, is explained by the absence of hydrogen bonds between neighboring molecules.

However, just like the chemical properties of esters, the physical properties depend on the structural features of the molecule. More precisely, on the type of alcohol and carboxylic acid from which it is formed. On this basis, esters are divided into three main groups:

Fruity esters. They are formed from lower carboxylic acids and the same monohydric alcohols. Liquids with characteristic pleasant floral and fruity odors.
Waxes. They are derivatives of higher (number of carbon atoms from 15 to 30) acids and alcohols, each having one functional group. These are plastic substances that soften easily in your hands. The main component of beeswax is myricyl palmitate C 15 H 31 COOC 31 H 63, and the Chinese one is cerotic acid ester C 25 H 51 COOC 26 H 53. They are insoluble in water, but soluble in chloroform and benzene.
Fats. Formed from glycerol and medium and higher carboxylic acids. Animal fats are usually solid under normal conditions, but melt easily when the temperature rises (butter, lard, etc.). Vegetable fats are characterized by a liquid state (linseed, olive, soybean oils). The fundamental difference in the structure of these two groups, which affects the differences in the physical and chemical properties of esters, is the presence or absence of multiple bonds in the acid residue. Animal fats are glycerides of unsaturated carboxylic acids, and vegetable fats are saturated acids.

Chemical properties

Esters react with nucleophiles, resulting in substitution of the alkoxy group and acylation (or alkylation) of the nucleophilic agent. If in structural formula ester has an α-hydrogen atom, then ester condensation is possible.

1. Hydrolysis. Acid and alkaline hydrolysis is possible, which is the reverse reaction of esterification. In the first case, hydrolysis is reversible, and the acid acts as a catalyst:

R-COO-R" + H 2 O<―>R-COO-H + R"-OH

Basic hydrolysis is irreversible and is usually called saponification, and sodium and potassium salts of fatty carboxylic acids are called soaps:

R-COO-R" + NaOH ―> R-COO-Na + R"-OΗ

2. Ammonolysis. Ammonia can act as a nucleophilic agent:

R-COO-R" + NH 3 ―> R-СО-NH 2 + R"-OH

3. Transesterification. This chemical property of esters can also be attributed to the methods of their preparation. Under the influence of alcohols in the presence of H + or OH -, it is possible to replace the hydrocarbon radical connected to oxygen:

R-COO-R" + R""-OH ―> R-COO-R"" + R"-OH

4. Reduction with hydrogen leads to the formation of molecules of two different alcohols:

R-СО-OR" + LiAlH 4 ―> R-СΗ 2 -ОХ + R"OH

5. Combustion is another typical reaction for esters:

2CΗ 3 -COO-CΗ 3 + 7O 2 = 6CO 2 + 6H 2 O

6. Hydrogenation. If there are multiple bonds in the hydrocarbon chain of an ether molecule, then the addition of hydrogen molecules is possible along them, which occurs in the presence of platinum or other catalysts. For example, it is possible to obtain solid hydrogenated fats (margarine) from oils.

Application of esters

Esters and their derivatives are used in various industries. Many of them dissolve various organic compounds well and are used in perfumery and the food industry, for the production of polymers and polyester fibers.

Ethyl acetate. Used as a solvent for nitrocellulose, cellulose acetate and other polymers, for the manufacture and dissolution of varnishes. Due to its pleasant aroma, it is used in the food and perfume industries.

Butyl acetate. Also used as a solvent, but also polyester resins.

Vinyl acetate (CH 3 -COO-CH=CH 2). It is used as a polymer base necessary in the preparation of glue, varnishes, synthetic fibers and films.

Malonic ether. Due to its special chemical properties, this ester is widely used in chemical synthesis for the production of carboxylic acids, heterocyclic compounds, and aminocarboxylic acids.

Phthalates. Esters of phthalic acid are used as plasticizing additives for polymers and synthetic rubbers, and dioctyl phthalate is also used as a repellent.

Methyl acrylate and methyl methacrylate. They easily polymerize to form sheets of organic glass that are resistant to various influences.