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. 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. 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, 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, 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
Fats, as it is not surprising, belong to esters. Stearic acid C 17 H 35 COOH (or other fatty acids close to it in composition and structure) and trihydric alcohol glycerol C 3 H 5 (OH) 3 participate in their formation. Here's what the molecule diagram of such an ether looks like:
H 2 C-O -C (O) C 17 H 35
HC-O-C(O)C 17 H 35
H 2 C-O -C (O) C 17 H 35 tristearin, ester of glycerol and stearic acid, glycerol tristearate.
Fats have a complex structure - this is confirmed by the model of the tristearate molecule.
Chemical properties of fats: hydrolysis and hydrogenation of liquid fats.
For fats containing residues of unsaturated carboxylic acids, all reactions of unsaturated compounds are characteristic. The most important addition reaction of practical importance is hydrogenation of liquid fats . This reaction underlies the production of margarine (solid fat) from vegetable oil.
All fats, like other esters, undergo hydrolysis .
Hydrolysis of fats also occurs in our body: when fats enter the digestive organs, they are hydrolyzed under the influence of enzymes to form glycerol and carboxylic acids. Hydrolysis products are absorbed by the intestinal villi, and then fat is synthesized, but already characteristic of this organism. Subsequently, they are hydrolyzed and gradually oxidized to carbon dioxide and water. When fats are oxidized in the body, a large amount of energy is released. For people engaged in heavy physical labor, the energy expended is most easily compensated by fatty foods. Fats supply fat-soluble vitamins and other biologically active substances to body tissues.
Depending on the conditions, hydrolysis happens:
¾ Water(without catalyst, at high temperature and pressure).
¾ Acid(in the presence of an acid as a catalyst).
¾ Enzymatic(occurs in living organisms).
¾ Alkaline (under the action of alkalis).
The hydrolysis of esters is a reversible reaction. To shift the equilibrium towards the reaction products, it is carried out in an alkaline medium (in the presence of alkalis or alkali metal carbonates, for example, sodium carbonate).
Hydrolysis of fats in an alkaline environment is called saponification of fats, because. salts of carboxylic acids are formed, which are called soaps .
Application of fats based on properties.
The use of fats .
Many fats when standing in the air rancid- acquire an unpleasant odor and taste, as ketones and aldehydes are formed. This process is stimulated by iron, so you can not leave the oil in the pan until the next day. Antioxidants are used to prevent it.
The souring of fat is associated with its hydrolysis. The sour taste is due to the presence of carboxylic acids.
Oil polymerization reactions are very important. On this basis, vegetable oils are divided into drying, semi-drying and non-drying. Drying in a thin layer form brilliant thin films. This is the basis for the use of these oils for the preparation of varnishes and paints (linseed). The drying floor includes, for example, sunflower oil, and the non-drying floor includes olive oil, which contains few unsaturated acids.
The biological role of fats.
Fats are of great practical importance and perform in our body multiple functions :
¾ Energy (with the complete breakdown of 1 g of fat to CO 2 and H 2 O, 38.9 kJ of energy is released).
¾ Structural (fats are an important component of every cell).
¾ Protective (fats accumulate in the subcutaneous tissues and tissues surrounding internal organs).
¾ Fats have low thermal conductivity and protect the body from hypothermia. Therefore, northerners consume a lot of animal fats.
Soap.
Soaps are sodium or potassium salts of higher carboxylic acids. Sodium salts of higher carboxylic acids have a solid state of aggregation, and potassium salts have a liquid (liquid soap).
In the manufacture of soap, fragrant substances, glycerin, dyes, antiseptics, and plant extracts are added to it.
The raw materials for making soap are vegetable oils (sunflower, cottonseed, etc.), animal fats, as well as sodium hydroxide or soda ash. Vegetable oils are preliminarily hydrogenated, that is, they are converted into solid fats. Fat substitutes are also used - synthetic carboxylic fatty acids with a higher molecular weight.
Fats are esters of the trihydric alcohol glycerol and higher carboxylic acids, the general formula of which is shown on the slide.
Fats, as it is not surprising, belong to esters. Stearic acid C 17 H 35 COOH (or other fatty acids close to it in composition and structure) and trihydric alcohol glycerol C 3 H 5 (OH) 3 participate in their formation. Here's what the molecule diagram of such an ether looks like:
H 2 C-O -C (O) C 17 H 35
HC-O-C(O)C 17 H 35
H 2 C-O -C (O) C 17 H 35 tristearin, ester of glycerol and stearic acid, glycerol tristearate.
Fats have a complex structure - this is confirmed by the model of the tristearate molecule.
Chemical properties of fats: hydrolysis and hydrogenation of liquid fats.
For fats containing residues of unsaturated carboxylic acids, all reactions of unsaturated compounds are characteristic. The most important addition reaction of practical importance is hydrogenation of liquid fats . This reaction underlies the production of margarine (solid fat) from vegetable oil.
All fats, like other esters, undergo hydrolysis .
Hydrolysis of fats also occurs in our body: when fats enter the digestive organs, they are hydrolyzed under the influence of enzymes to form glycerol and carboxylic acids. Hydrolysis products are absorbed by the intestinal villi, and then fat is synthesized, but already characteristic of this organism. Subsequently, they are hydrolyzed and gradually oxidized to carbon dioxide and water. When fats are oxidized in the body, a large amount of energy is released. For people engaged in heavy physical labor, the energy expended is most easily compensated by fatty foods. Fats supply fat-soluble vitamins and other biologically active substances to body tissues.
Depending on the conditions, hydrolysis happens:
¾ Water(without catalyst, at high temperature and pressure).
¾ Acid(in the presence of an acid as a catalyst).
¾ Enzymatic(occurs in living organisms).
¾ Alkaline (under the action of alkalis).
The hydrolysis of esters is a reversible reaction. To shift the equilibrium towards the reaction products, it is carried out in an alkaline medium (in the presence of alkalis or alkali metal carbonates, for example, sodium carbonate).
Synthesis of fats
In 1854 the French chemist Marcel Berthelot(1827-1907) carried out the reaction of esterification, that is, the formation of an ester between glycerol and fatty acids, and thus synthesized fat for the first time.
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
The composition and structure of fats
Fats are esters of the trihydric alcohol glycerol and higher carboxylic acids (Fig. 1).
Rice. 1. General formula of fat
Hydrocarbon radicals Ra, Rb, Rc in the composition of a fat molecule can be either the same or different, but as a rule, with a large number of carbon atoms (more than 15). For example, glycerol tristearate contains C17H35COOH stearic acid residues.
Some fats also contain residues of lower acids, for example, butter contains hydrocarbon radicals C3H7, which are part of butyric acid C3H7COOH.
The use of fats
- food industry
- pharmaceuticals
- Manufacture of soap and cosmetic products
- Lubricant production
Fats are food. The biological role of fats.
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". Basically, it is spent to maintain the normal temperature of the human body, as well as to work various muscles, so even when a person does nothing (for example, sleeps), he needs about 350 kJ of energy every hour to cover energy costs, about the same power has an electric 100 - watt bulb.
To provide the body with energy in adverse 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 (especially this function of fat is important for marine animals). For thousands of years, people have been doing hard 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 from food, but their amount should not exceed 100 g (this gives a third of the calorie content of 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 foods: in a small amount 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 also special varieties of 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 averaged, 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 during 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. 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 finished form. 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. For comparison: butter contains 45-50% saturated fatty acids, 22-27% unsaturated and less than 1% polyunsaturated. In this respect, high-quality margarine is healthier than butter.
Need to remember
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 qualities, only milk fat should not be consumed, since no fat contains an ideal composition of fatty acids. It is best to consume fats of both animal and vegetable 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 physical exertion, if there is little fat in the diet, as well as in severe illness, 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 heart disease, hypertension, etc.
Fats
Secondly, fats in the body serve as a reserve nutrient.
In addition, fats accumulate in the subcutaneous tissues and tissues surrounding the internal organs, performing a protective and heat-insulating function.
Foods such as margarine and mayonnaise are obtained from fats. In addition to being eaten, fats are used to make soaps, lubricants, cosmetics, candles, glycerin, drying oils.
SOURCES
video source - http://www.youtube.com/watch?v=7CBOPKQFwsA
http://interneturok.ru/ru/school/chemistry/10-klass - abstract
presentation source - http://pwpt.ru/download/advert/df0795ec49374f4fbb0383127b141166/
(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.
Lesson content lesson summary support frame lesson presentation accelerative methods interactive technologies Practice tasks and exercises self-examination workshops, trainings, cases, quests homework discussion questions rhetorical questions from students Illustrations audio, video clips and multimedia photographs, pictures graphics, tables, schemes humor, anecdotes, jokes, comics parables, sayings, crossword puzzles, quotes Add-ons abstracts articles chips for inquisitive cheat sheets textbooks basic and additional glossary of terms other Improving textbooks and lessonscorrecting errors in the textbook updating a fragment in the textbook elements of innovation in the lesson replacing obsolete knowledge with new ones Only for teachers perfect lessons calendar plan for the year methodological recommendations of the discussion program Integrated Lessons