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

People have long learned to isolate fat from natural objects and use it in Everyday life. Fat burned in primitive lamps, illuminating the caves primitive people, skids were lubricated with fat, along which ships were launched. Fats are the main source of our nutrition. But malnutrition, a sedentary lifestyle leads to overweight. 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 form one of the main parts of our food. Sources of fats are living organisms. Among the animals are cows, pigs, sheep, chickens, seals, whales, geese, fish (sharks, codfish, herring). From the liver of cod and shark, fish oil is obtained - a medicine, from herring - fats used to feed farm animals. Vegetable fats are most often liquid, they are called oils. Fats of plants such as cotton, flax, soybeans, peanuts, sesame, rapeseed, sunflower, mustard, corn, poppy, hemp, coconut, sea buckthorn, dogrose, oil palm and many others are used.

Back in the 17th century. German scientist, one of the first analytical chemists Otto Tachenius (1652–1699) was the first to suggest that fats contain a “hidden acid”. In 1741, the 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 greasy to the touch. The fact that fats and oils contain glycerin was first discovered in 1779 by the famous Swedish chemist Carl Wilhelm Scheele. For the first time chemical composition fats were identified at the beginning of the last century by the French chemist 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 Animal Bodies" by Mr. E. Chevreul established the structure of fats, thanks to the reaction of hydrolysis of fats in an alkaline medium. 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, decomposes into glycerol and acids.

Fat classification

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

Natural fats contain the following fatty acids

Physical Properties fat

• Animal fats (mutton, pork, beef, etc.) are usually solids with a low melting point (fish oil is an exception). Saturated acids predominate in solid fats.
• Vegetable fats - oils (sunflower, soybean, cottonseed, etc.) - liquids (exception - coconut oil, cocoa bean oil). Oils contain mainly residues of unsaturated (unsaturated) acids.

Chemical properties of fats

1. Hydrolysis, or saponification, of fats occurs under the action of water, with the participation of enzymes or acid catalysts (reversibly), while alcohol is formed - glycerol and a mixture of carboxylic acids:

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 - the transformation of liquid vegetable oils into solid fats great importance for food purposes. The product of the hydrogenation of oils is solid fat (artificial lard, salomas). Margarine- edible fat, consists of a mixture of hydrogenated oils (sunflower, corn, cottonseed, etc.), animal fats, milk and flavorings (salt, sugar, vitamins, etc.).

This is how margarine is obtained in industry:

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

The use of fats

o food industry

o pharmaceuticals

o Manufacture of soap and cosmetic products

o Lubricant production

10.5. Complex ethers. Fats

Esters- functional derivatives of carboxylic acids,
in the molecules of 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 the general formula:

Physical properties:

· Volatile, colorless liquids

Poorly soluble in water

More often with a pleasant smell

Lighter than water

Esters are found in flowers, fruits, berries. They determine their specific smell.
Are integral part essential oils(about 3000 ef.m. are known - orange, lavender, pink, 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	Formic acid amyl ester
Pear	Acetic acid isoamyl ester
A pineapple	Butyric acid ethyl ester (ethyl butyrate)
Banana	Acetic acid isobutyl ester (Isoamyl acetate also smells like a banana)
Jasmine	Acetic benzyl ether (benzylacetate)

Short names of esters are built 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 ester of acetic acid CH 3 COO C 2 H 5 called ethyl acetate.

Application

· As fragrances and odor intensifiers in the food and perfumery (manufacturing of soap, perfumes, creams) industries;

· In the production of plastics, rubber as plasticizers.

plasticizers – substances that are included polymer materials to impart (or increase) elasticity and (or) plasticity during processing and operation.

Application in medicine

AT late XIX- 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 medicines, as salol, validol, etc. As a local irritant and analgesic, methyl salicylate was widely used, which has now been practically superseded by more effective agents.

Obtaining 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 splitting of an ester by the action of water to form a carboxylic acid and an alcohol - is called ester hydrolysis.

RCOOR " + H 2 O ( H +) ↔ RCOOH + R "OH

Hydrolysis in the presence of alkali proceeds irreversibly (because 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 the alkaline hydrolysis of ester bonds in fats in the production of soap).

Fats, their structure, properties and applications

"Chemistry everywhere, chemistry in everything:

In everything we breathe

In everything we drink

Everything we eat."

In everything we wear

People have long learned to isolate fat from natural objects and use it in everyday life. Fat burned in primitive lamps, illuminating the caves of primitive people, grease was smeared on skids, along which ships were launched. Fats are the main source of our nutrition. But malnutrition, a sedentary lifestyle leads to overweight. 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 form one of the main parts of our food. Sources of fats are living organisms. Among the animals are cows, pigs, sheep, chickens, seals, whales, geese, fish (sharks, codfish, herring). From the liver of cod and shark, fish oil is obtained - a medicine, from herring - fats used to feed farm animals. Vegetable fats are most often liquid, they are called oils. Fats of plants such as cotton, flax, soybeans, peanuts, sesame, rapeseed, sunflower, mustard, corn, poppy, hemp, coconut, sea buckthorn, dogrose, oil palm and many others are used.

Fats perform various functions: building, energy (1 g of fat gives 9 kcal of energy), protective, storage. Fats provide 50% of the energy required by a person, so a person needs to consume 70-80 g 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, 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, in the body, fats are solvents for flavors and dyes. Many vitamins, such as vitamin A, are soluble only in fats.

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

Fats increase the effect of food satiety, as they are digested very slowly and delay the onset of hunger .

The history of the discovery of fats

Back in the 17th century. German scientist, one of the first analytical chemists Otto Tachenius(1652-1699) first suggested that fats contain a "hidden acid".

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

The fact that glycerin is included in the composition of fats and oils was first discovered in 1779 by the famous Swedish chemist Carl Wilhelm Scheele.

For the first time, the chemical composition of fats was determined at the beginning of the last century by a French chemist Michel Eugene Chevreul, the founder of the chemistry of fats, the author of numerous studies of their nature, summarized in a six-volume monograph "Chemical studies of bodies of animal origin".

1813 E. Chevreul established the structure of fats, thanks to the reaction of hydrolysis of fats in an alkaline medium. 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, decomposes into glycerol and acids.

Synthesis of fats

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.

Fat classification

Animal fats contain mainly glycerides of saturated acids and are solids. Vegetable fats, often referred to as 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)	COMPOSED ANIMALS FAT
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)	COMPOSED vegetal FAT

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

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

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

Chemical properties of fats

1. Hydrolysis, or saponification , fat occurs under the action of water, with the participation of enzymes or acid catalysts (reversibly), in this case, an alcohol is formed - glycerol and a mixture of carboxylic acids:

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

This is how margarine is obtained in industry:

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

The reaction for obtaining fats (esterification)

The use of fats

Fats are food. 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 of fat when completely oxidized (it takes place in cells with the participation of oxygen) gives 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 practically do not contain 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 rightly be considered a high-calorie "fuel". It is mainly used to maintain normal temperature human body, as well as for the work of various muscles, so even when a person does nothing (for example, sleeps), every hour he needs about 350 kJ of energy to cover energy costs, about the same power has an electric 100-watt light bulb.

To provide the body with energy adverse conditions it creates fat reserves that are deposited in the subcutaneous tissue, in the fatty fold of the peritoneum - the so-called omentum. Subcutaneous fat protects the body from hypothermia (especially this function of fat is important for marine animals). For millennia, people have performed heavy physical work, which required a lot of energy and, accordingly, enhanced nutrition. Only 50 g of fat is enough to cover the minimum daily human need for energy. However, with moderate physical activity an adult should receive slightly more fat with food, but their amount should not exceed 100 g (this gives a third of the calorie content for a diet of about 3000 kcal). It should be noted that half of these 100 g is found in food in the form of so-called hidden fat. Fats are found in almost all food products: in not in large numbers they are even in potatoes (there are 0.4%), in bread (1-2%), in oatmeal (6%). Milk usually contains 2-3% fat (but there are special varieties skimmed milk). 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. Fats in almost pure form are lard and vegetable oil; in butter about 80% fat, in ghee - 98%. Of course, all the above 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 products. It is not so easy to “work off” extra calories through physical activity. For example, jogging 7 km, a person spends about the same amount of energy as he receives by eating just one hundred-gram bar of chocolate (35% fat, 55% carbohydrates). Physiologists have found that with physical activity, which is 10 times higher than usual, a person who received a 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, "allocate" it much faster. Therefore, before physical activity, it is preferable to eat sweet rather than fatty foods. An excess of fats in food, especially animal fats, also increases the risk of developing diseases such as atherosclerosis, heart failure, etc. There is a lot of cholesterol in animal fats (but we should not forget that two-thirds of cholesterol is synthesized in the body from non-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 be supplied to the body in ready-made. Of these, arachidonic acid has the highest activity (it is synthesized in the body from linoleic acid), the least activity is linolenic acid (10 times lower than linoleic acid). According to various estimates, the daily human need for linoleic acid ranges from 4 to 10 g. Most of all linoleic acid (up to 84%) is in safflower oil, squeezed from safflower seeds, an annual plant with bright orange flowers. A lot of this acid is also found in sunflower and nut oils.

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

Must be remembered!!!

Saturated fatty acids negatively affect fat metabolism, liver function and contribute to the development of atherosclerosis. Unsaturated (especially linoleic and arachidonic acids) regulate fat metabolism and are involved in the removal of cholesterol from the body. The higher the content of unsaturated fatty acids, the lower the melting point of the fat. The calorie content of solid animal 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, remaining in the form of an emulsion, is easily absorbed by the body. Despite these positive traits, you can not use only milk fat, since no fat contains an ideal composition of fatty acids. It is best to consume fats from both animal and plant origin. Their ratio should be 1:2.3 (70% animal and 30% vegetable) for young people and middle-aged people. The diet of older people should be dominated by vegetable fats.

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, keeping proteins for life. This fat provides energy during exercise, if there is little fat in the diet, and also when serious illnesses when, due to reduced appetite, it is not enough supplied with food.

Abundant consumption of fat with 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 disease heart disease, hypertension, etc.

EXERCISES

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

Decision:

It is known that carbon monoxide ( IV ) is released when sodium carbonate reacts with acid. There can be only one acid of 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 were also 1 mol of acid in the mixture. Molar mass of initial organic compounds is equal to: M (C 3 H 6 O 2) \u003d 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 of C 3 H 6 O 2 corresponds to two esters: ethyl formate HSOOS 2 H 5 and methyl acetate CH 3 SOOSH 3. Esters of formic acid react with an ammonia solution of silver oxide, so the first ester does not satisfy the condition 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. Relative density ester vapor for hydrogen is 44. During the hydrolysis of this ester, two compounds are formed, the combustion of equal amounts of which produces the same volumes of carbon dioxide (under the same conditions). Give the structural formula of this ester.

Decision:

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

M (C n H 2 n O 2) \u003d 14 n + 32 = 44 . 2 = 88 g/mol,

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

CH 3 -		O-S 2 H 5

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

________________________________________________________________

3. In the hydrolysis of an ester, molar mass which is equal to 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 weight. Alcohol B is not oxidized by sodium dichromate and easily reacts with hydrochloric acid to form alkyl chloride.

Decision:

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) \u003d M (A g )/0.5966 = 181 g/mol, whence M (R ) \u003d 181- (12 + 2. 16 + 108) \u003d 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 ') \u003d M (C 2 H 5 COOR ') - M (C 2 H 5 COO) \u003d 130-73 \u003d 57 g / mol. This radical has molecular formula C 4 H 9 . By condition, alcohol C 4 H 9 OH is not oxidized Na 2 C r 2 About 7 and easy to react 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-butyl propionate:

		CH 3
C 2 H 5 —	C-O-	C-CH3
		CH 3

Answer . tert-butyl propionate.

________________________________________________________________

4. Write two possible formulas for a fat that has 57 carbon atoms in a molecule and reacts with iodine in a ratio of 1:2. The composition of fat contains residues of acids with an even number of carbon atoms.

Decision:

General formula for fats:

where R, R', R "- hydrocarbon radicals containing not even 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 for three radicals. If two double bonds are in the same radical, then the fat contains a residue of linoleic acid ( R \u003d 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 \u003d R ' \u003d 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

________________________________________________________________

5.

________________________________________________________________

TASKS FOR INDEPENDENT SOLUTION

1. What is an esterification reaction.

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

3. What are Chemical properties 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 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 was taken if 13.44 liters of hydrogen (n.o.) 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 propanol-2 are heated in the presence of concentrated sulfuric acid, if 24 g of the ester is formed.

9. For the hydrolysis of a fat sample weighing 221 g, it took 150 g of sodium hydroxide solution with a mass fraction of alkali of 0.2. Suggest the structural formula of the original fat.

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

VIDEO EXPERIENCE

1. What reaction underlies the preparation 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

Fats and oils are natural esters that are formed by a trihydric alcohol - glycerol and higher fatty acids with an unbranched carbon chain containing an even number of carbon atoms. In turn, sodium or potassium salts of higher fatty acids are called soaps.

When carboxylic acids interact with alcohols ( esterification reaction) esters are formed:

This reaction is reversible. The reaction products can interact with each other to form the initial substances - alcohol and acid. Thus, the reaction of esters with water - ester hydrolysis - is the reverse of the esterification reaction. Chemical equilibrium, which is established when the rates of direct (esterification) and reverse (hydrolysis) reactions are equal, can be shifted towards the formation of ether by the presence of water-removing agents.

Esters in nature and technology

Esters are widely distributed in nature, are used in technology and various industries industry. They are good solvents organic substances, 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 are highly flammable liquids with low boiling points and smell of various fruits. They are used as solvents for varnishes and paints, flavoring products Food Industry. For example, butyric acid methyl ester has the smell of apples, the ethyl ester of this acid has the smell of pineapples, the isobutyl ester of acetic acid has the smell of bananas:

Esters of higher carboxylic acids and higher monobasic alcohols are called waxes. So, beeswax is the main
together from an ester of palmitic acid and 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.

Fats

The most important representatives of esters are fats.

Fats- natural compounds that are esters of glycerol and higher carboxylic acids.

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

Most fats are formed by three carboxylic acids: oleic, palmitic and stearic. Obviously, two of them are limiting (saturated), and oleic acid contains a double bond between carbon atoms in the molecule. Thus, 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 in their composition are most often liquid. They are called oils. Basically, these are fats of vegetable origin - linseed, hemp, sunflower and other oils. Less common are liquid fats of animal origin, such as fish oil. Most natural fats of animal origin under normal conditions are solid (fusible) substances and contain mainly residues of saturated carboxylic acids, for example, mutton fat. So, palm oil is a solid fat under normal conditions.

The composition of fats determines their physical and chemical properties. It is clear that for fats containing residues of unsaturated carboxylic acids, all reactions of unsaturated compounds are characteristic. They decolorize bromine water, 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:

hydrolysis:

Soaps

All fats, like other esters, undergo hydrolysis. The hydrolysis of esters is a reversible reaction. To shift the equilibrium towards 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 proceeds irreversibly and leads to the formation of salts of carboxylic acids, which are called soaps. Hydrolysis of fats in an alkaline environment is called saponification of fats.

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

Crib

(esterification reaction) esters are formed:

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, which is established when the rates of direct (esterification) and reverse (hydrolysis) reactions are equal, can be shifted towards the formation of ether by the presence of water-removing agents.

Esters in nature and technology

Esters are widely distributed in nature and are used in engineering and various industries (Scheme 10). They are good solvents of organic substances, their density is less than that of water, and they practically do not dissolve in it.

Scheme 10. The use of esters

Thus, esters with a relatively small molecular weight are flammable liquids with low boiling points and smell of various fruits. They are used as solvents for varnishes and paints, flavorings of food industry products. For example, butyric acid methyl ester has the smell of apples, the ethyl ester of this acid has the smell of pineapples, and the isobutyl ester of acetic acid has the smell of bananas.

Esters of higher carboxylic acids and higher monobasic alcohols are called say. So, beeswax consists mainly of the ester of palmitic acid and myricyl alcohol C15H31COOC31H63, sperm whale wax - spermaceti - an ester of the same palmitic acid and cetyl alcohol C15H31COOC16H33.

The most important representatives of esters are fats.

Fats - natural compounds that are esters of glycerol and higher carboxylic acids.

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

Most fats are formed by three carboxylic acids - oleic, palmitic and stearic. Obviously, two of them are limiting (saturated), and oleic acid contains a double bond between carbon atoms in the molecule. Thus, the composition of fats can include residues of both saturated and unsaturated carboxylic acids in various combinations.

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