Fats, not surprisingly, are esters. Their formation involves stearic acid C 17 H 35 COOH (or others similar in composition and structure fatty acids) and trihydric alcohol glycerol C 3 H 5 (OH) 3. This is what the diagram of the molecule of such an ether looks like:
H 2 C-O –C(O)C 17 H 35
NS-O –C(O)C 17 N 35
H 2 C- O –C(O)C 17 H 35 tristearin, ester of glycerol and stearic acid, glycerol tristearate.
Fats have complex structure– this confirms 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, are subject to hydrolysis .
Hydrolysis of fats also occurs in our body: when fats enter the digestive organs, under the influence of enzymes they are hydrolyzed to form glycerol and carboxylic acids. Hydrolysis products are absorbed by the intestinal villi, and then fat is synthesized, but already characteristic to a given organism. Subsequently, they hydrolyze and gradually oxidize to carbon dioxide and water. When fats are oxidized in the body, they release large number energy. For people engaged in heavy physical labor, the energy expended is easiest to compensate fatty foods. Fats are supplied to body tissues fat soluble vitamins and other biological active substances.
Depending on the conditions, hydrolysis occurs:
¾ Water(without catalyst, with high temperatures and pressure).
¾ Acid(in the presence of acid as a catalyst).
¾ Enzymatic(occurs in living organisms).
¾ Alkaline (under the influence of alkalis).
Hydrolysis of esters – reversible reaction. To shift the equilibrium towards the reaction products, it is carried out in an alkaline environment (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.
Application of fats .
Many fats when standing in the air go rancid– acquire an unpleasant odor and taste, as ketones and aldehydes are formed. This process is stimulated by iron, so you should not leave oil in the pan until next day. Antioxidants are used to prevent it.
Acidification of fat is associated with its hydrolysis. The sour taste is due to the appearance of carboxylic acids.
Polymerization reactions of oils are very important. On this basis vegetable oils They are divided into drying, semi-drying and non-drying. Drying in thin layer form shiny thin films. This is the basis for the use of these oils for the preparation of varnishes and paints (linseed oil). Drying ones include, for example, sunflower, and non-drying ones include olive, which contains few unsaturated acids.
Biological role fat
Fats are of great practical importance and perform in our body several 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 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 state (liquid soap).
When making soap, aromatic substances, glycerin, dyes, antiseptics, and plant extracts are added to it.
The starting materials for soap production are vegetable oils (sunflower, cottonseed, etc.), animal fats, as well as sodium hydroxide or soda ash. Vegetable oils are first hydrogenated, i.e. they are converted into solid fats. Fat substitutes are also used - synthetic carboxylic fatty acids with a higher molecular weight.
Lipid oxidation – is the main cause of damage to cell membranes, for example when radiation sickness. However, in vivo LPO constantly occurs even without the presence of radiation. The oxidation of iron (Fe+2) produces hydroxyl radicals (H-O)– and hydroperoxide radicals (H-O-O)–, which initiate lipid oxidation. The reaction has a chain nature and occurs with residues of unsaturated fatty acids:
2) Hydrolysis of fats in alkaline the medium gives glycerol and soluble salts of carboxylic acids:
3) As a result of fat oxidation, along with the release of energy, quite a lot of water is formed. If there is a shortage drinking water this makes it easier to tolerate thirst:
4) Hydrogenation of fats - the transformation of liquid vegetable oils into solid fats - has great value for food purposes. It comes with high temperature or high blood pressure in the presence of special catalysts. This is how margarine is produced in industry.
Slide 40 –
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Fats, not surprisingly, are esters. Their formation involves stearic acid C17H35COOH (or other fatty acids similar in composition and structure) and trihydric alcohol glycerol C3H5(OH)3. This is what the diagram of the molecule of such an ether looks like:
Н2С-О –С(О)С17Н35
NS-O –C(O)C17N35
H2C-O –C(O)C17H35 tristearin, glycerol stearic acid ester, 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, are subject to hydrolysis .
Hydrolysis of fats also occurs in our body: when fats enter the digestive organs, under the influence of enzymes they are hydrolyzed to form glycerol and carboxylic acids. The products of hydrolysis are absorbed by the intestinal villi, and then fat is synthesized, but already characteristic of a given organism. Subsequently, they hydrolyze and gradually oxidize to carbon dioxide and water. When fats are oxidized, a large amount of energy is released in the body. For people engaged in heavy physical labor, the easiest way to compensate for the energy expended is with fatty foods. Fats supply fat-soluble vitamins and other biologically active substances to the body tissues.
Depending on the conditions, hydrolysis occurs:
¾ Water(without catalyst, at high temperature and pressure).
¾ Acid(in the presence of acid as a catalyst).
¾ Enzymatic(occurs in living organisms).
¾ Alkaline (under the influence of alkalis).
Hydrolysis of esters is a reversible reaction. To shift the equilibrium towards the reaction products, it is carried out in an alkaline environment (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.
Application of fats .
Many fats when standing in the air go rancid– acquire an unpleasant odor and taste, as ketones and aldehydes are formed. This process is stimulated by iron, so you should not leave the oil in the pan until the next day. Antioxidants are used to prevent it.
Acidification of fat is associated with its hydrolysis. The sour taste is due to the appearance of carboxylic acids.
Polymerization reactions of oils are very important. Based on this criterion, vegetable oils are divided into drying, semi-drying and non-drying. Dries in a thin layer to form shiny thin films. This is the basis for the use of these oils for the preparation of varnishes and paints (linseed oil). Drying ones include, for example, sunflower, and non-drying ones include olive, which contains few unsaturated acids.
Biological role of fats.
Fats are of great practical importance and perform in our body several functions :
¾ Energy (with the complete breakdown of 1 g of fat to CO2 and H2O, 38.9 kJ of energy is released).
¾ Structural (fats are an important component of every cell).
¾ Protective (fats accumulate in 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 state (liquid soap).
When making soap, aromatic substances, glycerin, dyes, antiseptics, and plant extracts are added to it.
The starting materials for soap production are vegetable oils (sunflower, cottonseed, etc.), animal fats, as well as sodium hydroxide or soda ash. Vegetable oils are first hydrogenated, i.e. they are converted into solid fats. Fat substitutes are also used - synthetic carboxylic fatty acids with a higher molecular weight.
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Fats- these are esters of glycerol and higher fatty carboxylic acids (the trivial name is glycerides).
Solid fats(animal fats) – contain residues of saturated higher carboxylic acids.
Liquid fats (oils) – glycerides of unsaturated higher carboxylic acids.
Higher carboxylic acids that are part of fats always have an even number of carbon atoms (C8 - C18) and an unbranched hydrocarbon residue.
Natural fats and oils are mixtures of glycerides of higher carboxylic acids.
General formula of fats (oils)
The composition of solid fats most often includes the following saturated acids:
C17 H35 COOH - octadecane, stearic acid
C15 H31 COOH - octahexane, palmitic acid
Stearates and palmitates are the basis butter, beef, pork fats.
The composition of oils or liquid fats most often includes glycerides of the following unsaturated acids:
These acids in the form of glycerides are found in olive, cottonseed, soybean, corn and flaxseed oils.
Physical properties
Fats are insoluble in water, do not have a clear melting point and increase significantly in volume when melted.
The solid aggregate state of fats is due to the fact that these fats contain residues of saturated acids and fat molecules are capable of dense packing. The oils contain residues of unsaturated acids in the cis configuration; dense packing of molecules is impossible, therefore the state of aggregation is liquid.
Reactivity
Fats (oils) are esters and are characterized by all ester reactions.
We will describe only two industrially important reactions - alkaline hydrolysis (saponification) of fats and hydrogenation of oils.
1. Saponification– alkaline hydrolysis of fats, production of soap.
Soaps are mixtures of sodium (potassium) salts of higher saturated carboxylic acids (sodium soap is solid, potassium soap is 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 (practically, they 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 similarly charged micelles repel each other, and the pollutant and water turn into an emulsion (practically, it is dirty water).
Soap hydrolysis also occurs in water, creating an alkaline environment:
C17 H35 COONa C17 H35 COOH + NaOH
Soaps should not be used in harsh or sea water, since the resulting calcium (magnesium) stearates are insoluble in water.
Synthetic soap substitutes(synthetic detergent compounds - SMC).
SMS– substances of various classes of organic compounds containing a bulky non-polar residue (lipophilic region) and a polar residue (hydrophilic region) containing a sulfo group.
1. Alkyl sulfates– sodium salts of hydrosulfates of higher alcohols (hydrosulfates are esters of alcohols and sulfuric acid).
Lauryl hydrogen sulfate in the form of sodium salt is the basis of shampoos and other liquid cosmetics.
2. Alkylbenzenesulfonates– sodium salts of alkylbenzenesulfonic acids (the basis of washing powders).
Advantages of SMS:
a) can be used in hard water, since their calcium and magnesium salts are soluble in water;
b) do not hydrolyze, because are derivatives of a strong acid. The alkaline environment created when using soap (a salt of weak stearic acid upon hydrolysis produces an alkaline environment) contributes to the partial destruction of washed fabrics.
From the point of view of chemical structure, fats are esters formed by the interaction of glycerol with higher saturated and unsaturated acids, i.e. derivatives of higher carboxylic acids, alcohols and other compounds.
General structural formula and classification of fats.
Hydrolysis of fats is one of the most important properties of compounds of this class. This reaction is otherwise called saponification. This reaction can occur in an acidic, alkaline or alcoholic environment. During hydrolysis, lipids break down into their constituent substances: glycerol and acids. For example, if fat is formed by glycerin and stearic acid, the output we will get are these products:
Fat hydrolysis refers to the hydrolytic breakdown of glycerides.
Apply four main fat hydrolysis method :
1) Saponification of fats with water lead under the influence enzymes or sulfuric acid:
Hydrolysis of lipids, leading to the formation of bad-smelling carboxylic acids (for example, butyric acid);
1) Rancidity - lipid peroxidation
 |
Lipid oxidation – is the main cause of damage to cell membranes, for example during radiation sickness.
However, in vivo LPO constantly occurs even without the presence of radiation. The oxidation of iron (Fe+2) produces hydroxyl radicals (H-O)– and hydroperoxide radicals (H-O-O)–, which initiate lipid oxidation. The reaction has a chain nature and occurs with residues of unsaturated fatty acids:
As a result, aldehydes and carboxylic acids are formed, membranes are damaged, and radical metabolites have mutagenic and carcinogenic effects. Antioxidants, such as vitamin E, protect against lipid oxidation.
Glycerol, which is part of the fat, undergoes oxidation and dehydration when the fat is heated with conc. sulfuric acid. Feels like bad smell acrolein. This is an “acrolein test” that allows you to distinguish fats from fat-like substances.
Slide 37 - Alkaline hydrolysis of phospholipids produces: glycerol, carboxylic acid salts, sodium phosphate and alcohol
Slide 38 - Quantitative characteristics For unsaturated lipids, the iodine number is used, which corresponds to the mass of iodine (in grams) that can be added to 100 g of lipid.
Slide 40 –
Fats and oils are natural esters that are formed by triatomic alcohol - glycerol and higher fatty acids with a straight carbon chain containing even number 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 starting materials - 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 ester by the presence of water-removing agents.
Esters are widespread in nature and are used in technology 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 have the odors of various fruits. They are used as solvents for varnishes and paints, and as product flavoring agents. food industry. For example, the methyl ester of butyric acid 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 waxes. Thus, beeswax consists mainly of
at once from the 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.
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 from three carboxylic acids: oleic, palmitic and stearic. Obviously, two of them are saturated (saturated), and oleic acid contains a double bond between the carbon atoms in the molecule. Thus, the composition of fats may include residues of both saturated and unsaturated carboxylic acids in various combinations.
IN normal conditions fats containing residues of unsaturated acids are most often liquid. They are called oils. Mostly fats plant origin- flaxseed, hemp, sunflower and other oils. Less common are liquid fats of animal origin, for example 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. So, palm oil- fat that is hard 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 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:
hydrolysis:
All fats, like other esters, are subject to hydrolysis. 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 occurs 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, glycerin and soaps are formed - sodium or potassium salts of higher carboxylic acids:
(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 opposite 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 agents.
Esters in nature and technology
Esters are widespread in nature and are used in technology and various industries (Scheme 10). They are good solvents of organic substances, their density is less than the density of water, and they practically do not dissolve in it.
Scheme 10. Application of esters
Thus, esters with a relatively small molecular weight 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 flavoring agents for food industry products. For example, the methyl ester of butyric acid 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 voskazhi. Thus, beeswax consists mainly of an 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 from three carboxylic acids - oleic, palmitic and stearic. Obviously, two of them are saturated (saturated), and oleic acid contains a double bond between the carbon atoms in the molecule. Thus, the composition of fats may include residues of both saturated and unsaturated carboxylic acids in various combinations.
Lesson content lesson notes supporting frame lesson presentation acceleration methods interactive technologies Practice tasks and exercises self-test workshops, trainings, cases, quests homework discussion questions rhetorical questions from students Illustrations audio, video clips and multimedia photographs, pictures, graphics, tables, diagrams, humor, anecdotes, jokes, comics, parables, sayings, crosswords, quotes Add-ons abstracts articles tricks for the curious cribs textbooks basic and additional dictionary of terms other Improving textbooks and lessonscorrecting errors in the textbook updating a fragment in a textbook, elements of innovation in the lesson, replacing outdated knowledge with new ones Only for teachers perfect lessons calendar plan for the year methodological recommendations discussion programs Integrated LessonsSo far we have considered alcohols with one hydroxyl group ( HE). Such alcohols are called alcohols.
But alcohols are also known whose molecules contain several hydroxyl groups. Such alcohols are called polyatomic or polyalcohols.
Examples of such alcohols include dihydric alcohol ethylene glycol and trihydric alcohol glycerol:
Ethylene glycol and glycerin are sweetish-tasting liquids that can be mixed with water in any ratio.
Glycerol together with the highest fatty acids forms esters.
In the case of the interaction of glycerol with higher fatty acids, we obtain compounds whose molecules consist of several hydrocarbon radicals linked by an oxygen atom. One of these radicals is glycerol radical, the rest - higher fatty acid radicals.
The resulting molecule from the reaction is nothing more than a molecule fat. Thus, glycerol is integral part molecules, both plant and animal fats, including human body fats.
Simple saponifiable lipids. Waxes, fats and oils.
The group of “simple saponifiable lipids” includes waxes, fats and oils.
About the name
First, a few words about the name “Simple Saponifiable Lipids.”
Simple they are called because, unlike " complex lipids", they include only carbon atoms in their structure ( WITH), hydrogen ( H) and oxygen ( ABOUT).
Complex lipids They additionally contain atoms of other elements. Moreover, their structure is really more complex.
Saponifiable soap.
Waxes
Waxes are called esters of monohydric fatty alcohols and higher fatty acids.
Esters- these are compounds where hydrocarbon radicals (in in this case monohydric fatty alcohols and higher fatty acids) are interconnected through oxygen atom.
Radicals, however, can be different, but they will always be bound by an oxygen atom.
The reaction of forming an ester from an acid and an alcohol is called esterification reaction.
Waxes form a protective film on the skin of humans and animals and protect plants from drying out.
An example of wax is palmitic acid cetyl ester– the main component of spermaceti. Spermaceti found in spermaceti oil. Previously, this oil was extracted from the head of sperm whales and used as an indifferent base for the preparation of various ointments.
Another palmitic acid ester is myricyl palmitate– contained in beeswax.
Any natural wax always has complex composition. It's not just one ester, it's many different esters with different components.
Beeswax , in its composition, has about 50 substances. In addition to esters, these can be free fatty acids, fatty alcohols, vitamins, etc. But the basis of the substance will still be esters.
Fats and oils
By chemical structure fats close to waxes. No wonder they are combined into one group.
Just like waxes, fats This esters of higher fatty acids and alcohol.
But if included waxes may include various high molecular weight monohydric alcohols, then instead of them in the composition fat always included trihydric alcohol glycerin.
Let us remind you that alcohols these are derivatives of hydrocarbons in the molecules of which one or more hydrogen atoms are replaced by hydroxyl groups ( HE).
If in an alcohol molecule one hydroxyl group, then such an alcohol is called monatomic, if they more - polyatomic.
Glycerol contains three hydroxyl groups. Therefore, it is a trihydric alcohol:
High molecular weight(or higher fatty) are alcohols with relatively a large number carbon atoms. For example, the above cetyl alcohol C16H33OH or myricyl alcohol C 31 H 63 OH.
Glycerol C 3 H 5 (OH) 3 does not belong to higher fatty alcohols.
So, fats– these are esters of higher fatty acids and trihydric alcohol glycerol.
Such esters are called triglycerides.
Fats are triglycerides of higher fatty acids.
In living organisms fats, first of all, play a role structural component of cells or reserve substance(“fat depot”). Their energy value approximately 2 times higher than that of proteins and carbohydrates.
Along with carbohydrates and proteins, fats- one of the main components of nutrition.
Solid triglycerides are usually called fats, liquid - oils.
Simple triglycerides contain residues of identical acids, mixed- various.
By analogy with waxes we can say that natural fats And oils, both plants and animals are complex substances consisting of many components. They represent mixed triglyceride mixtures.
In triglycerides animal origin residues predominate saturated acids. These triglycerides are usually solids.
Against liquid vegetable oils contain mainly residues unsaturated acids.
Besides triglycerides they may contain free fatty acids, fatty alcohols, complex lipids, vitamins, etc.
Complex saponifiable lipids.
About the name
Let us recall that the large group of “Saponifiable lipids” is divided into two subgroups:
1. simple saponifiable lipids And
2. complex saponifiable lipids.
Saponifiable they are named because upon hydrolysis they form salts of higher carboxylic acids, i.e. soap.
Complex lipids got their name because they have a more complex structure compared to simple lipids (waxes and fats).
Molecules simple lipids consist of carbon atoms ( WITH), hydrogen ( H) and oxygen ( ABOUT).
The composition of molecules complex lipids, in addition to carbon, hydrogen and oxygen atoms, there are atoms of other elements. Most often it is: phosphorus ( R), sulfur ( S) and nitrogen ( N). At the same time structure of complex lipid molecules really more complex than the structure of simple lipid molecules.
Related information.
