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 ether 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 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. Common name such compounds are 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 fat

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. Molar mass of the starting materials organic compounds is equal to: 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 the 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 the chemical properties of fats.

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

5. Write structural formulas 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

The most important representatives of esters are fats.

Fats, oils

Fats- these are esters of glycerol and higher monoatomic . The general name of such compounds is triglycerides or triacylglycerols, where acyl is a carboxylic acid residue -C(O)R. The composition of natural triglycerides includes 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 glycerides of higher carboxylic acids.

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

Esterification- reaction of formation of esters.

The composition of fats may 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 - flaxseed, hemp, sunflower and other oils (with the exception of palm and coconut oils - solid under normal conditions). Less common are liquid fats of animal origin, such as fish oil. Most natural fats of animal origin under normal conditions are solid (low-melting) substances and contain mainly residues of saturated carboxylic acids, for example, lamb 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 increase significantly in volume when melted.

The aggregate state of fats is solid, this is due to the fact that fats contain residues of saturated acids and fat molecules are capable of dense packing. The composition of oils includes residues of unsaturated acids in the cis configuration, therefore dense 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 for fats containing residues of unsaturated carboxylic acids, all reactions of unsaturated compounds are characteristic. They decolorize 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 - a 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 ensure the formation of hydrolysis products, it is carried out in an alkaline environment (in the presence of alkalis or Na 2 CO 3). Under these conditions, the hydrolysis of fats occurs reversibly and leads to the formation of salts of carboxylic acids, which are called. fats in an alkaline environment are 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, production of soap.

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

Soaps are surfactants (abbreviated as surfactants, detergents). The detergent effect of soap is due to the fact that soap emulsifies fats. Soaps form micelles with pollutants (relatively, 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. The micelles are charged in the same way, therefore they repel, and the pollutant and water turn into an emulsion (practically, it is dirty water).

Soap also occurs in water, which creates an alkaline environment.

Soaps should not be used in harsh or sea water, since the resulting calcium (magnesium) stearates are insoluble in water.

When carboxylic acids react with alcohols (esterification reaction), they form esters:
R 1 -COOH (acid) + R 2 -OH (alcohol) ↔ R 1 -COOR 2 (ester) + H 2 O
This reaction is reversible. The reaction products can interact with each other to form the starting materials - alcohol and acid. Thus, the reaction of esters with water—ester hydrolysis—is the reverse of the esterification reaction. The chemical equilibrium established when the rates of forward (esterification) and reverse (hydrolysis) reactions are equal can be shifted towards the formation of ester by the presence of water-removing substances.

Esters in nature and technology

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

Formed as a result of the reaction of two alcohol molecules with each other, these are ethers. The bond is formed through an oxygen atom. During the reaction, a water molecule (H 2 O) is split off, and two hydroxyls interact with each other. According to nomenclature, symmetrical ethers, that is, consisting of identical molecules, can be called by trivial names. For example, instead of diethyl - ethyl. The names of compounds with different radicals are arranged alphabetically. According to this rule, methyl ethyl ether will sound correct, but vice versa it will not.

Structure

Due to the variety of alcohols that react, their interaction can result in the formation of ethers that differ significantly in structure. The general formula for the structure of these compounds looks like this: R-O-R ´. The letters “R” stand for alcohol radicals, that is, simply put, the rest of the hydrocarbon part of the molecule except the hydroxyl. If an alcohol has more than one such group, it can form several bonds with different compounds. Alcohol molecules can also have cyclic fragments in their structure and generally represent polymers. For example, when cellulose reacts with methanol and/or ethanol, ethers are formed. The general formula of these compounds when reacting with alcohols of the same structure looks the same (see above), but the hyphen is removed. In all other cases, it means that the radicals in the ether molecule can be different.

Cyclic ethers

A special type of ethers are cyclic. The best known among them are oxyethane and tetrahydrofuran. The formation of ethers of this structure occurs as a result of the interaction of two hydroxyls of one molecule of a polyhydric alcohol. As a result, a cycle is formed. Unlike linear ethers, cyclic esters are more capable of forming hydrogen bonds, and therefore they are less volatile and more soluble in water.

Properties of ethers

In physical terms, ethers are volatile liquids, but there are quite a lot of crystalline representatives.

These compounds are poorly soluble in water, and many of them have a pleasant odor. There is one quality due to which ethers are actively used as organic solvents in laboratories. The chemical properties of these compounds are quite inert. Many of them do not undergo hydrolysis - the reverse reaction that occurs with the participation of water and leads to the formation of two alcohol molecules.

Chemical reactions involving ethers

Chemical reactions of ethers are generally only feasible at high temperatures. For example, when heated to a temperature above 100 o C, methylphenyl ether (C 6 H 5 -O-CH 3) reacts with hydrobromic (HBr) or hydroiodic acid (HI) to form phenol and bromomethyl (CH 3 Br) or iodomethyl (CH 3 I), respectively.

Many representatives of this group of compounds, in particular methyl ethyl and diethyl ether, can react in the same way. A halogen usually attaches to a shorter radical, for example:

C 2 H 5 -O-CH 3 + HBr → CH 3 Br + C 2 H 5 OH.

Another reaction that ethers undergo is interaction with Lewis acids. This term refers to a molecule or ion that is an acceptor and combines with a donor that has a lone pair of electrons. Thus, boron fluoride (BF 3) and tin chloride (SnCI 4) can act as such compounds. Interacting with them, ethers form complexes called oxonium salts, for example:

C 2 H 5 -O-CH 3 + BF 3 → -B(-)F 3.

Methods for preparing ethers

The preparation of ethers occurs in different ways. One method is to dehydrate alcohols using concentrated sulfuric acid (H 2 SO 4) as a dewatering agent. The reaction takes place at 140 o C. In this way, only compounds from one alcohol are obtained. For example:

C 2 H 5 OH + H 2 SO 4 → C 2 H 5 SO 4 H + H 2 O;
C 2 H 5 SO 4 H + HOC 2 H 5 → C 2 H 5 -O-C 2 H 5 + H 2 SO 4.

As can be seen from the equations, the synthesis of diethyl ether occurs in 2 steps.

Another method for the synthesis of ethers is the Williamson reaction. Its essence lies in the interaction of potassium or sodium alcoholate. This is the name given to the products of replacement of the proton of the hydroxyl group of an alcohol with a metal. For example, sodium ethoxide, potassium isopropylate, etc. Here is an example of this reaction:

CH 3 ONa + C 2 H 5 Cl → CH 3 -O-C 2 H 5 + KCl.

Esters with double bonds and cyclic representatives

As in other groups of organic compounds, compounds with double bonds are found among the ethers. Among the methods for obtaining these substances there are special ones that are not typical for saturated structures. They involve the use of alkynes, at the triple bond of which oxygen is added and vinyl esters are formed.

Scientists have described the preparation of ethers of a cyclic structure (oxiranes) using the method of oxidation of alkenes with peracids containing a peroxide residue instead of a hydroxyl group. This reaction is also carried out under the influence of oxygen in the presence of a silver catalyst.

The use of ethers in laboratories involves the active use of these compounds as chemical solvents. Diethyl ether is popular in this regard. Like all compounds of this group, it is inert and does not react with substances dissolved in it. Its boiling point is just over 35 o C, which is convenient when quick evaporation is necessary.

Compounds such as resins, varnishes, dyes, and fats easily dissolve in ethers. Phenol derivatives are used in the cosmetics industry as preservatives and antioxidants. In addition, esters are added to detergents. Among these compounds, representatives with a pronounced insecticidal effect were found.

Cyclic ethers of complex structure are used in the production of polymers (glycolide, lactide, in particular) used in medicine. They perform the function of a biosorbable material, which, for example, is used for vascular bypass.

Cellulose ethers are used in many areas of human activity, including in the restoration process. Their function is to glue and strengthen the product. They are used in the restoration of paper materials, paintings, and fabrics. There is a special technique that involves dipping old paper into a weak (2%) solution of methylcellulose. Esters of this polymer are resistant to chemical reagents and extreme conditions environment, are non-flammable, therefore they are used to impart strength to any materials.

Some examples of the use of specific representatives of ethers

Ethers are used in many areas of human activity. For example, as an additive to motor oil (diisopropyl ether), coolant (diphenyl oxide). In addition, these compounds are used as intermediate products for the production of drugs, dyes, and aromatic additives (methylphenyl and ethylphenyl ethers).

An interesting ether is dioxane, which has good solubility in water and allows this liquid to be mixed with oils. The peculiarity of its production is that two molecules of ethylene glycol are connected to each other via hydroxyl groups. As a result, a six-membered heterocycle with two oxygen atoms is formed. It is formed under the action of concentrated sulfuric acid at 140 o C.

Thus, ethers, like all classes organic chemistry, are very diverse. Their feature is chemical inertness. This is due to the fact that, unlike alcohols, they do not have a hydrogen atom on oxygen, so it is not as active. For the same reason, ethers do not form hydrogen bonds. It is because of these properties that they are able to mix with various kinds of hydrophobic components.

In conclusion, I would like to note that diethyl ether is used in genetics experiments to euthanize fruit flies. This is just a small part of where these connections are used. It is quite possible that in the future, based on ethers, a number of new durable polymers with an improved structure compared to existing ones will be produced.

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)

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).