Organic substances, classes of organic substances. Theory of the chemical structure of organic compounds. Classification of organic substances

Functional group

Name

hydrocarbons

Acetylene

Halogen compounds

Halogen derivatives

–Hal (halogen)

Ethyl chloride, ethyl chloride

Oxygen compounds

Alcohols, phenols

CH 3 CH 2 OH

Ethyl alcohol, ethanol

Ethers

CH 3 -O-CH 3

dimethyl ether

Aldehydes

Acetic aldehyde, ethanal

Acetone, propanone

carboxylic acids

Acetic acid, ethanoic acid

Esters

Acetic acid ethyl ester, ethyl acetate

Acid halides

Acetic acid chloride, acetyl chloride

Anhydrides

Acetic anhydride

Acetic acid amide, acetamide

Nitrogen compounds

Nitro compounds

Nitromethane

ethylamine

Acetonitrile, acetic acid nitrile

Nitroso compounds

Nitrosobenzene

Hydrocompounds

Phenylhydrazine

Azo compounds

C 6 H 5 N=NC 6 H 5

Azobenzene

Diazonium salts

Phenyldiazonium chloride

Basic connection

Name

Radical structure

Name

Monovalent radicals

CH 3 -CH 2 -

CH 3 -CH 2 -CH 3

CH 3 -CH 2 -CH 2 -

Isopropyl ( second- propyl)

CH 3 -CH 2 -CH 2 -CH 3

CH 3 -CH 2 -CH 2 -CH 2 -

second-Butyl

Isobutane

Isobutyl

tert-Butyl

CH 3 (CH 2) 3 CH 3

CH 3 (CH 2) 3 CH 2 –

(n-amyl)

Isopentane

Isopentyl (isoamyl)

Neopentane

Neopentyl

CH 2 \u003d CH–CH 2 -

CH 3 -CH=CH-

propenil

Organic substances, unlike inorganic substances, form the tissues and organs of living organisms. These include proteins, fats, carbohydrates, nucleic acids, and others.

The composition of organic substances of plant cells

These substances are chemical compounds that contain carbon. Rare exceptions to this rule are carbides, carbonic acid, cyanides, carbon oxides, carbonates. Organic compounds are formed when carbon bonds with any of the elements of the periodic table. Most often, these substances contain oxygen, phosphorus, nitrogen, hydrogen.

Each cell of any of the plants on our planet consists of organic substances, which can be conditionally divided into four classes. These are carbohydrates, fats (lipids), proteins (proteins), nucleic acids. These compounds are biological polymers. They take part in metabolic processes in the body of both plants and animals at the cellular level.

Four classes of organic substances

1. - these are compounds, the main building blocks which are amino acids. In the plant body, proteins perform various important features, the main of which is structural. They are part of a variety of cell formations, regulate life processes and are stored in reserve.

2. are also included in absolutely all living cells. They are made up of the simplest biological molecules. These are esters of carboxylic acids and alcohols. The main role of fats in the life of cells is energy. Fats are deposited in seeds and other parts of plants. As a result of their splitting, the energy necessary for the life of the body is released. In winter, many shrubs and trees feed on the reserves of fats and oils that they have accumulated over the summer. It should also be noted the important role of lipids in the construction of cell membranes - both plant and animal.

3. Carbohydrates are the main group of organic substances, due to the breakdown of which organisms receive the necessary energy for life. Their name speaks for itself. In the structure of carbohydrate molecules, along with carbon, oxygen and hydrogen are present. The most common storage carbohydrate produced in cells during photosynthesis is starch. A large amount of this substance is deposited, for example, in the cells of potato tubers or cereal seeds. Other carbohydrates provide sweet taste plant fruits.

Organic substances of goods are compounds that include carbon and hydrogen atoms. They are divided into monomers, oligomers and polymers.

Monomers- organic substances consisting of one compound and not subjected to splitting with the formation of new organic substances. The breakdown of monomers occurs mainly to carbon dioxide and water.

Monosaccharides - monomers belonging to the class of carbohydrates, whose molecules include carbon, hydrogen and oxygen (CH2O)n. The most widespread of these are hexoses(С6Н12О6) - glucose and fructose. They are found mainly in foods plant origin(fruits and vegetables, flavored drinks and confectionery). The industry also produces pure glucose and fructose as a food product and raw material for the production of confectionery and drinks for diabetics. From natural products honey contains the most glucose and fructose (up to 60%).

Monosaccharides give the products a sweet taste, have an energy value (1 g - 4 kcal) and affect the hygroscopicity of the products containing them. Solutions of glucose and fructose are well fermented by yeast and are used by other microorganisms, therefore, at a content of up to 20% and an increased water content, they worsen the shelf life.

organic acids Compounds containing one or more carboxyl groups (-COOH) in their molecules.

Depending on the number of carboxyl groups, organic acids are divided into mono-, di- and tricarboxylic acids. Other classification features of these acids are the number of carbon atoms (from C2 to C40), as well as amino and phenol groups.

Natural organic acids are found in fresh fruits and vegetables, their processed products, flavor products, as well as in fermented milk products, cheeses, fermented milk butter.

organic acids compounds that give foods a sour taste. Therefore, they are used in the form of food additives as acidifiers (acetic, citric, lactic and other acids) for sugary confectionery, alcoholic and non-alcoholic drinks, sauces.

The most common in food products are lactic, acetic, citric, malic and tartaric acids. Certain types of acids (citric, benzoic, sorbic) have bactericidal properties, so they are used as preservatives. Organic acids of food products are additional energy substances, since energy is released during their biological oxidation.

Fatty acid - carboxylic acids of the aliphatic series, having at least six carbon atoms in the molecule (C6-C22 and above). They are divided into higher (HFA) and low molecular weight (SFA).

The most important natural saturated fatty acids are stearic and palmitic, and the unsaturated ones are oleic, arachidonic, linoleic and linolenic. Of these, the last two are polyunsaturated essential fatty acids, which determine the biological effectiveness of food products. Natural fatty acids can be found as fats in all fat-containing foods, but they are found in free form in small amounts, as well as EFAs.

Amino acids - carboxylic acids containing one or more amino groups (NH2).

Amino acids in products can be found in free form and as part of proteins. In total, about 100 amino acids are known, of which almost 80 are found only in free form. Glutamic acid and its sodium salt are widely used as a food additive in seasonings, sauces, food concentrates based on meat and fish, as they enhance the taste of meat and fish.

vitamins - low molecular weight organic compounds that are regulators or participants in metabolic processes in the human body.

Vitamins can independently participate in metabolism (for example, vitamins C, P, A, etc.) or be part of enzymes that catalyze biochemical processes (vitamins B1, B2, B3, B6, etc.).

In addition to these general properties, each vitamin has specific functions and properties. These properties are considered within the discipline "Physiology of Nutrition".

Vitamins are classified according to their solubility as follows:

• on the water soluble(B1, B2, B3, PP, B6, B9, B12, C, etc.);
• fat-soluble(A, D, E, K).

The group of vitamins also includes vitamin-like substances some of which are called vitamins (carotene, choline, vitamin U, etc.).

Alcohols - organic compounds containing in the molecules one or more hydroxyl groups (OH) at saturated carbon atoms. According to the number of these groups, one-, two- (glycols), three- (glycerol) and polyhydric alcohols are distinguished. Ethyl alcohol is obtained as a finished product in the alcohol industry, as well as in winemaking, distillery, brewing industry, in the production of wines, vodkas, cognac, rum, whiskey, beer. Besides, ethanol in small quantities it is formed during the production of kefir, koumiss and kvass.

Oligomers- organic substances, consisting of 2-10 residues of molecules of homogeneous and heterogeneous substances.

Depending on the composition, oligomers are divided into one-component, two-, three- and multicomponent ones. To one-component oligomers include some oligosaccharides (maltose, trehalose), two-component - sucrose, lactose, monoglyceride fats, which include the remains of glycerol molecules and only one fatty acid, as well as glycosides, esters; to three-component - raffinose, diglyceride fats; to multicomponent - fats-triglycerides, lipoids: phosphatides, waxes and steroids.

Oligosaccharides - carbohydrates, which include 2-10 residues of monosaccharide molecules linked by glycosidic bonds. There are di-, tri- and tetrasaccharides. Disaccharides - sucrose and lactose, to a lesser extent - maltose and trehalose, as well as trisaccharides - raffinose, have the greatest distribution in food products. These oligosaccharides are found only in food products.

sucrose(beet or cane sugar) is a disaccharide consisting of residues of glucose and fructose molecules. During acid or enzymatic hydrolysis, sucrose breaks down into glucose and fructose, a mixture of which in a 1: 1 ratio is called invert sugar. As a result of hydrolysis, the sweet taste of foods is enhanced (for example, when fruits and vegetables ripen), since fructose and invert sugar have a higher degree of sweetness than sucrose. So, if the degree of sweetness of sucrose is taken as 100 conventional units, the degree of sweetness of fructose will be 220, and invert sugar - 130.

Sucrose is the predominant sugar in the following food products: granulated sugar, refined sugar (99.7-99.9%), sugary confectionery products (50-96%), some fruits and vegetables (bananas - up to 18%, melons - up to 12%, onions - up to 10-12%), etc. In addition, sucrose can be contained in small amounts in other food products of plant origin (grain products, many alcoholic and non-alcoholic drinks, low-alcohol cocktails, flour confectionery), as well as sweet dairy products - ice cream, yogurt, etc. Sucrose is not found in foods of animal origin.

Lactose (milk sugar) - a disaccharide consisting of residues of glucose and galactose molecules. During acidic or enzymatic hydrolysis, lactose breaks down to glucose and galactose, which are used by living organisms: humans, yeast, or lactic acid bacteria.

Lactose, in terms of sweetness, is significantly inferior to sucrose and glucose, which is part of it. It is inferior to them in terms of prevalence, as it is found mainly in the milk of different animal species (3.1-7.0%) and individual products of its processing. However, when using lactic acid and/or alcohol fermentation in the production process (for example, fermented milk products) and/or rennet(in the production of cheese) lactose is completely fermented.

Maltose (malt sugar) is a disaccharide consisting of two residues of glucose molecules. This substance is found as a product of incomplete hydrolysis of starch in malt, beer, bread and flour confectionery products made using sprouted grains. It is found only in small quantities.

Trehalose (mushroom sugar) is a disaccharide consisting of two residues of glucose molecules. This sugar is not widely distributed in nature and is found mainly in foods of one group - fresh and dried mushrooms, as well as in natural canned food of them and yeast. In fermented (salted) mushrooms, trehalose is absent, since it is consumed during fermentation.

Rafinose - trisaccharide, consisting of residues of glucose, fructose and galactose molecules. Like trehalose, raffinose is a rare substance found in small amounts in grain flour products and beets.

Properties. All oligosaccharides are reserve nutrients of plant organisms. They are highly soluble in water, easily hydrolyzed to monosaccharides, have a sweet taste, but the degree of their sweetness is different. The only exception is raffinose - unsweetened in taste.

Oligosaccharides hygroscopic, at high temperatures (160-200 ° C) they caramelize with the formation of dark-colored substances (caramelins, etc.). In saturated solutions, oligosaccharides can form crystals, which in some cases worsen the texture and appearance of products, causing the formation of defects (for example, candied honey or jam; formation of lactose crystals in sweetened condensed milk).

Lipids and lipoids - oligomers, which include the remains of molecules of the trihydric alcohol glycerol or other high molecular weight alcohols, fatty acids, and sometimes other substances.

Lipids are oligomers that are esters of glycerol and fatty acids - glycerides. A mixture of natural lipids, mainly triglycerides, is called fats. Products contain fats.

Depending on the number of residues of fatty acid molecules in glycerides, there are mono, di and triglycerides, and depending on the predominance of saturated or unsaturated acids, fats are liquid and solid. liquid fats are most often of vegetable origin (for example, vegetable oils: sunflower, olive, soybean, etc.), although there are also solid vegetable fats (cocoa butter, coconut, palm kernel). Solid fats- these are mainly fats of animal or artificial origin (beef, mutton fat; cow butter, margarine, cooking fats). However, among animal fats there are also liquid ones (fish, whale, etc.).

Depending on the quantitative content of fats, all consumer goods can be divided into the following groups.

1. Super High Fat Products (90.0-99.9%). These include vegetable oils, animal and cooking fats, and ghee.

2. Products with a predominant fat content (60-89.9%) are represented butter, margarine, pork fat, nuts: walnuts, pine nuts, hazelnuts, almonds, cashews, etc.

3. Foods high in fat (10-59%). This group includes concentrated dairy products: cheeses, ice cream, canned milk, sour cream, cottage cheese, cream with high fat content, mayonnaise; fatty and medium fat meat, fish and products of their processing, fish roe; egg; non-fat soy and products of its processing; cakes, pastries, butter biscuits, nuts, peanuts, chocolate products, halva, fat-based creams, etc.

4. Products low in fat (1.5-9.9%) - legumes, snack and lunch canned food, milk, cream, except for high-fat, sour-milk drinks, certain types low-fat fish (for example, the cod family) or meat of the II category of fatness and offal (bones, heads, legs, etc.).

5. Very low fat products (0.1-1.4%) - the majority of grain flour and fruit and vegetable products.

6. Products that do not contain fat (0%), - low-alcohol and non-alcoholic drinks, sugary confectionery products, except for caramel and sweets with milk and nut fillings, toffee; sugar; honey.

General properties. Fats are reserve nutrients, have the highest energy value among other nutrients (1 g - 9 kcal), as well as biological efficiency if they contain polyunsaturated essential fatty acids. Fats have a relative density less than 1, so they are lighter than water. They are insoluble in water, but soluble in organic solvents (gasoline, chloroform, etc.). With water, fats in the presence of emulsifiers form food emulsions (margarine, mayonnaise).

Fats undergo hydrolysis under the action of the enzyme lipase or saponification under the action of alkalis. In the first case, a mixture of fatty acids and glycerol is formed; in the second - soaps (salts of fatty acids) and glycerin. Enzymatic hydrolysis of fats can also occur during storage of goods. The amount of free fatty acids formed is characterized by the acid number.

The digestibility of fats largely depends on the intensity of lipases, as well as the melting point. Liquid fats with a low melting point are absorbed better than solid fats with a high melting point. The high intensity of fat absorption in the presence of a large amount of these or other energy substances (for example, carbohydrates) leads to the deposition of their excess in the form of fat depot and obesity.

Fats containing unsaturated (unsaturated) fatty acids are capable of oxidation with the subsequent formation of peroxides and hydroperoxides, which have harmful effect on the human body. Products with rancid fats are no longer safe and must be destroyed or recycled. Rancidity of fats is one of the criteria for the expiration date or storage of fat-containing products (oatmeal, wheat flour, biscuits, cheeses, etc.). The ability of fats to go rancid is characterized by iodine and peroxide numbers.

Liquid fats with a high content of unsaturated fatty acids can enter into a hydrogenation reaction - saturation of such acids with hydrogen, while the fats acquire a solid consistency and function as substitutes for some solid animal fats. This reaction is the basis for the production of margarine and margarine products.

Lipoids - fat-like substances, whose molecules include residues of glycerol or other high-molecular alcohols, fatty and phosphoric acids, nitrogenous and other substances.

Lipoids include phosphatides, steroids and waxes. They differ from lipids in the presence of phosphoric acid, nitrogenous bases, and other substances that are absent in lipids. These are more complex substances than fats. Most of them are united by the presence of fatty acids in the composition. The second component - alcohol - can have a different chemical nature: in fats and phosphatides - glycerol, in steroids - high-molecular cyclic sterols, in waxes - higher fatty alcohols.

Closest in chemical nature to fats phosphatides(phospholipids) - esters of glycerol of fatty and phosphoric acids and nitrogenous bases. Depending on the chemical nature nitrogenous base, the following types of phosphatides are distinguished: lecithin (the new name is phosphatidylcholine), which contains choline; as well as cephalin containing ethanolamine. Lecithin has the greatest distribution in natural products and application in the food industry. Egg yolks, offal (brains, liver, heart), milk fat, legumes, especially soy are rich in lecithin.

Properties. Phospholipids have emulsifying properties, due to which lecithin is used as an emulsifier in the production of margarine, mayonnaise, chocolate, ice cream.

Steroids and waxes are esters of high molecular weight alcohols and high molecular weight fatty acids (C16-C36). They differ from other lipoids and lipids by the absence of glycerol in their molecules, and from each other by alcohols: steroids contain residues of sterol molecules - cyclic alcohols, and waxes are monohydric alcohols with 12-46 C atoms in the molecule. The main plant sterol is β-sitosterol, animals - cholesterol, microorganisms - ergosterol. Vegetable oils are rich in sitosterol, cow butter, eggs, offal are rich in cholesterol.

Properties. Steroids are insoluble in water, are not saponified by alkalis, have a high melting point, and have emulsifying properties. Cholesterol and ergosterol can be converted to vitamin D by exposure to ultraviolet light.

Glycosides - oligomers, in which the remainder of the molecules of monosaccharides or oligosaccharides is associated with the remainder of a non-carbohydrate substance - aglucone through a glycosidic bond.

Glycosides are found only in food products, mainly of plant origin. They are especially abundant in fruits, vegetables and their processed products. The glycosides of these products are represented by amygdalin (in the kernels of stone fruits, almonds, especially bitter ones), solanine and chaconine (in potatoes, tomatoes, eggplants); hesperidin and naringin (in citrus fruits), sinigrin (in horseradish, radish), rutin (in many fruits, as well as buckwheat). Small amounts of glycosides are also found in animal products.

Properties. glycosides are soluble in water and alcohol, many of them have a bitter and / or burning taste, a specific aroma (for example, amygdalin has a bitter almond aroma), bactericidal and medicinal properties (for example, sinigrin, cardiac glycosides, etc.).

Ethers - oligomers, in the molecule of which the remains of the molecules of their constituent substances are united by simple or complex ether bonds.

Depending on these bonds, ethers and esters are distinguished.

• Simple ethers are part of household chemicals (solvents) and perfumes and cosmetics. They are absent in food products, but can be used as auxiliary raw materials in the food industry.
• Esters- compounds consisting of residues of molecules of carboxylic acids and alcohols.

Esters of lower carboxylic acids and simplest alcohols have a pleasant fruity odor, which is why they are sometimes called fruit esters.

Complex (fruit) esters together with terpenes and their derivatives, aromatic alcohols (eugenol, linalool, anethole, etc.) and aldehydes (cinnamon, vanilla, etc.) are part of essential oils that determine the aroma of many foods (fruits, berries, wines, liqueurs, confectionery). Esters, their compositions and essential oils are an independent product - food additives, such as flavorings.

Properties. Esters are easily volatile, insoluble in water, but soluble in ethyl alcohol and vegetable oils. These properties are used to extract them from spicy-aromatic raw materials. Esters are hydrolyzed under the action of acids and alkalis with the formation of carboxylic acids or their salts and alcohols included in their composition, and also enter into condensation reactions to form polymers and transesterification to obtain new esters by replacing one alcohol or acid residue.

Polymers- macromolecular substances, consisting of tens or more residues of molecules of homogeneous or dissimilar monomers connected by chemical bonds.

They are characterized by a molecular weight of several thousand to several million oxygen units and consist of monomeric units. Monomer link(previously called elementary)- a compound link that is formed from one molecule of monomer during polymerization. For example, in starch - C6H10O5. With an increase in the molecular weight and the number of units, the strength of polymers increases.

According to their origin, polymers are divided into natural, or biopolymers (e.g. proteins, polysaccharides, polyphenols, etc.), and synthetic (e.g. polyethylene, polystyrene, phenolic resins). Depending on the location in the macromolecule of atoms and atomic groups, there are linear polymers open linear chain (e.g. natural rubber, cellulose, amylose), branched polymers, having a linear chain with branches (for example, amylopectin), globular polymers, characterized by the predominance of the forces of intramolecular interaction between groups of atoms that make up the molecule over the forces of intermolecular interaction (for example, proteins in the muscle tissue of meat, fish, etc.), and network polymers with three-dimensional networks formed by segments of high-molecular compounds of a chain structure (for example, cast phenolic resins). There are other structures of polymer macromolecules (ladder, etc.), but they are rare.

According to the chemical composition of the macromolecule, homopolymers and copolymers are distinguished. Homopolymers - high-molecular compounds consisting of the monomer of the same name (for example, starch, cellulose, inulin, etc.). copolymers - compounds formed from several different monomers (two or more). Examples are proteins, enzymes, polyphenols.

Biopolymers - natural macromolecular compounds formed during the life of plant or animal cells.

In biological organisms, biopolymers perform four important functions:

1) rational storage of nutrients that the body consumes when there is a shortage or absence of their intake from the outside;

2) formation and maintenance of tissues and systems of organisms in a viable state;

3) ensuring the necessary metabolism;

4) protection from external adverse conditions.

The listed functions of biopolymers continue to perform partially or completely in goods, the raw materials for which are certain bioorganisms. At the same time, the predominance of certain functions of biopolymers depends on what needs are satisfied by specific products. For example, food products fulfill primarily energy and plastic needs, as well as the need for internal security, therefore, their composition is dominated by reserve digestible (starch, glycogen, proteins, etc.) and indigestible (cellulose, pectin substances) or hardly digestible biopolymers (some proteins), characterized by high mechanical strength and protective properties. Fruit and vegetable products contain biopolymers that have a bactericidal effect, which ensures additional protection from adverse external influences, primarily of a microbiological nature.

Biopolymers of food products are represented by digestible and indigestible polysaccharides, pectin substances, digestible and difficult or indigestible proteins, as well as polyphenols.

In food products of plant origin, the predominant biopolymers are polysaccharides and pectin substances, and in products of animal origin, proteins. Known products of plant origin, consisting almost entirely of polysaccharides with a small amount of impurities (starch and starch products). In animal products, polysaccharides are practically absent (the exception is animal meat and liver, which contain glycogen), but products that consist only of protein are also absent.

Polysaccharides - These are biopolymers containing oxygen and consisting of a large number of monomer units such as C5H8O4 or C6H10O5.

According to the digestibility of the human body, polysaccharides are divided into digestible(starch, glycogen, inulin) and indigestible(cellulose, etc.).

Polysaccharides are predominantly formed plant organisms, therefore, they are quantitatively predominant substances of food products of plant origin (70-100% of dry matter). The only exception is glycogen, the so-called animal starch, which is formed in the liver of animals. Different classes and groups of goods differ in subgroups of predominant polysaccharides. So, in grain flour products (except soy), flour confectionery, potatoes and nuts, starch predominates. In fruit and vegetable products (except potatoes and nuts), sugary confectionery products, starch is either absent or contained in small quantities. In these products, the main carbohydrates are mono- and oligosaccharides.

Starch - a biopolymer consisting of monomer units - glucoside residues.

Natural starch is represented by two polymers: linear amylose and branched amylopectin, the latter predominating (76-84%). In plant cells, starch is formed in the form of starch granules. Their size, shape, as well as the ratio of amylose and amylopectin are identifying features of certain types of natural starch (potato, corn, etc.). Starch is a reserve substance of plant organisms.

Properties. Amylose and amylopectin differ not only in structure, but also in properties. Amylopectin with a large molecular weight (100,000 or more) is insoluble in water, and amylose is soluble in hot water and forms weakly viscous solutions. The formation and viscosity of starch paste are largely due to amylopectin. Amylose is more easily hydrolyzed to glucose than amylopectin. During storage, aging of starch occurs, as a result of which its water-holding capacity decreases.

• Foods high in starch(50-80%), represented by grain and flour products - grain, cereals, except legumes; pasta and crackers, as well as a food additive - starch and modified starch.
• Medium starch foods(10-49%). These include potatoes, legumes, except soybeans, which lack starch, bread, flour confectionery, nuts, unripe bananas.
• Foods low in starch(0.1-9%): most fresh fruits and vegetables, except those listed, and their processed products, yogurt, ice cream, boiled sausages and other combined products, the production of which uses starch as a consistency stabilizer or thickener.

There is no starch in other food products.

Glycogen - reserve polysaccharide of animal organisms. It has a branched structure and is similar in structure to amylopectin. The largest number it is found in the liver of animals (up to 10%). In addition, it is found in muscle tissue, the heart, the brain, as well as in yeast and mushrooms.

Properties. Glycogen forms colloidal solutions with water, hydrolyzes to form glucose, gives a red-brown color with iodine.

Cellulose (fiber) - a linear natural polysaccharide, consisting of residues of glucose molecules.

Properties. Cellulose is a polycyclic polymer with a large number of polar hydroxyl groups, which gives rigidity and strength to its molecular chains (and also increases moisture capacity, hygroscopicity). Cellulose is insoluble in water, resistant to weak acids and alkalis, and soluble only in very few solvents (copper-ammonia solvent and concentrated solutions of quaternary ammonium bases).

pectin substances - a complex of biopolymers, the main chain of which consists of residues of galacturonic acid molecules.

Pectin substances are represented by protopectin, pectin and pectin acid, which differ in molecular weight, degree of polymerization and the presence of methyl groups. Their common property is insolubility in water.

Protopectin - a polymer, the main chain of which consists of a large number of monomer units - the remnants of pectin molecules. Protopectin includes araban and xylan molecules. It is part of the median lamellae that bind individual cells into tissues, and together with cellulose and hemicelluloses - into the shells of plant tissues, providing their hardness and strength.

Properties. Protopectin undergoes acid and enzymatic hydrolysis (for example, during the ripening of fruits and vegetables), as well as destruction during prolonged cooking in water. As a result, the tissues soften, which facilitates the absorption of food by the human body.

Pectin - a polymer consisting of residues of methyl ester molecules and unmethylated galacturonic acid. Pectins of different plants differ in different degrees of polymerization and methylation. This affects their properties, in particular, the gelling ability, due to which pectin and fruits containing it in sufficient quantities are used in the confectionery industry in the production of marmalade, marshmallow, jam, etc. The gelling properties of pectin increase with an increase in its molecular weight and degree of methylation.

Properties. Pectin undergoes saponification under the action of alkalis, as well as enzymatic hydrolysis with the formation of pectin acids and methyl alcohol. Pectin is insoluble in water, not absorbed by the body, but has a high water-retaining and sorption capacity. Thanks to the latter property, it removes many harmful substances from the human body: cholesterol, salts of heavy metals, radionuclides, bacterial and fungal poisons.

Pectin substances are found only in unrefined food products of plant origin (grain and fruit and vegetable products), as well as in products with the addition of pectin or vegetable raw materials rich in it (fruit and berry confectionery, whipped sweets, cakes, etc.).

Squirrels - natural biopolymers, consisting of residues of amino acid molecules linked by amide (peptide) bonds, and separate subgroups additionally contain inorganic and organic nitrogen-free compounds.

Therefore, by chemical nature, proteins can be organic, or simple, polymers and organoelemental, or complex, copolymers.

Simple proteins consist only of residues of amino acid molecules, and complex proteins in addition to amino acids, they can contain inorganic elements (iron, phosphorus, sulfur, etc.), as well as nitrogen-free compounds (lipids, carbohydrates, dyes, nucleic acids).

Depending on the ability to dissolve in various solvents, simple proteins are divided into the following types: albumins, globulins, prolamins, glutelins, protamines, histones, proteoids.

Complex proteins are subdivided depending on the nitrogen-free compounds that make up their macromolecules into the following subgroups:

• phosphoroproteins - proteins containing residues of phosphoric acid molecules (milk casein, egg vitellin, fish roe ichthulin). These proteins are insoluble but swell in water;
• glycoproteins - proteins containing residues of carbohydrate molecules (mucins and mucoids of bones, cartilage, saliva, as well as the cornea of ​​​​the eyes, the mucous membrane of the stomach, intestines);
• lipoproteins - proteins with the remains of lipid molecules (contained in membranes, protoplasm of plant and animal cells, blood plasma, etc.);
• chromoproteins - proteins with residues of molecules of coloring compounds (myoglobin of muscle tissue and hemoglobin of blood, etc.);
• nucleoproteins - proteins with nucleic acid residues (proteins of cell nuclei, germs of seeds of cereals, buckwheat, legumes, etc.).

The composition of proteins can include 20-22 amino acids in different ratios and sequences. These amino acids are divided into essential and non-essential.

Essential amino acids - amino acids that are not synthesized in the human body, so they must come from the outside with food. These include isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, arginine, and histidine.

Non-essential amino acids - amino acids synthesized in the human body.

Depending on the content and optimal ratio of essential amino acids, proteins are divided into complete and inferior.

Complete proteins - proteins, which include all the essential amino acids in the optimal ratio for the human body. These include proteins of milk, eggs, muscle tissue of meat and fish, buckwheat, etc.

Incomplete proteins Proteins that are missing or deficient in one or more essential amino acids. These include proteins of bones, cartilage, skin, connective tissues, etc.

According to digestibility, proteins are divided into digestible(muscle proteins, milk, eggs, cereals, vegetables, etc.) and indigestible(elastin, collagen, keratin, etc.).

Protein macromolecules have a complex structure. There are four levels of organization of protein molecules: primary, secondary, tertiary and quaternary structures. primary structure called the sequence of amino acid residues in the polypeptide chain, connected by an amide bond. secondary structure refers to the type of stacking of polypeptide chains, most often in the form of a spiral, the turns of which are held by hydrogen bonds. Under tertiary structure understand the location of the polypeptide chain in space. In many proteins, this structure is formed from several compact globules called domains and connected by thin bridges - elongated polypeptide chains. Quaternary structure reflects the way of association and arrangement in space of macromolecules, consisting of several polypeptide chains not connected by covalent bonds.

Hydrogen, ionic and other bonds arise between these subunits. Changes in pH, temperature, treatment with salts, acids, and the like lead to the dissociation of the macromolecule into the original subunits, but when these factors are eliminated, spontaneous reconstruction of the quaternary structure occurs. Deeper changes in the structure of proteins, including the tertiary one, are called denaturation.

Proteins are found in many food products: vegetable origin - grain flour, fruits and vegetables, flour confectionery products and animal origin - meat, fish and dairy products. In a number of food products, proteins are either completely absent, or their content is negligible and is not essential in nutrition, although it can affect precipitation or turbidity (for example, in juices).

Properties. The physicochemical properties of proteins are determined by their high molecular nature, the compactness of the polypeptide chains, and the mutual arrangement of amino acids. The molecular weight of proteins varies from 5 thousand to 1 million.

In food products highest value have the following properties: the energy value, enzymatic and acid hydrolysis, denaturation, swelling, melanoidin formation.

The energy value protein is 4.0 kcal per 1 g. However, the biological value of proteins, determined by the content of essential amino acids, is more important for the human body.

Enzymatic and acid hydrolysis of proteins occurs under the influence of proteolytic enzymes and hydrochloric acid of gastric juice. Due to this property, digestible proteins are used by the human body, and the amino acids formed during hydrolysis are involved in the synthesis of proteins in the human body. Hydrolysis of proteins occurs during the fermentation of dough, the production of alcohol, wines and beer, pickled vegetables.

Protein denaturation occurs by reversible and profound irreversible changes in the structure of the protein. Reversible denaturation is associated with changes in the quaternary structure, and irreversible - in the secondary and tertiary structures. Denaturation occurs under the action of high and low temperatures, dehydration, a change in the pH of the medium, an increased concentration of sugars, salts and other substances, while the digestibility of proteins improves, but the ability to dissolve in water and other solvents, as well as to swell, is lost. The process of protein denaturation is one of the most significant in the production of many food products and culinary products (baking bakery and flour confectionery products, pickling vegetables, milk, salting fish and vegetables, drying, canning with sugar and acids).

Swelling, or hydration, of proteins - their ability to absorb and retain bound water while increasing the volume. This property is the basis for the preparation of dough for bakery and flour confectionery products, in the production of sausages, etc. Preservation of proteins in a swollen state is important task many foods containing them. The loss of water-holding capacity of proteins, called syneresis, causes aging of proteins of flour and cereals, especially legumes, staleness of bakery and flour confectionery products.

Melanoidin formation- the ability of protein amino acid residues to interact with reducing sugars to form dark-colored compounds - melanoidins. This property is most pronounced when elevated temperatures and pH from 3 to 7 in the production of bakery and flour confectionery, beer, canned food, dried fruits and vegetables. As a result, the color of the products changes from yellow-gold to brown. different shades and black, while reducing the biological value of products.

Enzymes - biopolymers of protein nature, which are catalysts for many biochemical processes.

The main function of enzymes is to accelerate the transformation of substances that enter, or are available, or are formed during the metabolism in any biological organism (human, animals, plants, microorganisms), as well as the regulation of biochemical processes depending on changing external conditions.

Depending on the chemical nature of macromolecules, enzymes are divided into one- and two-component. One-component consist only of protein (for example, amylase, pepsin, etc.), two-component- from protein and non-protein compounds. On the surface of a protein molecule or in a special slot are active centers, represented by a set of functional groups of amino acids that directly interact with the substrate, and / or non-protein components - coenzymes. The latter include vitamins (B1, B2, PP, etc.), as well as minerals (Cu, Zn, Fe, etc.). So, iron-containing enzymes include peroxidase and catalase, and copper-containing enzymes - ascorbate oxidase.

• oxidoreductase - enzymes that catalyze redox reactions by transferring hydrogen ions or electrons, for example, respiratory enzymes peroxidase, catalase;
• transferase- enzymes that catalyze the transfer of functional groups (CH3, COOH, NH2, etc.) from one molecule to another, for example, enzymes that catalyze the deamination and decarboxylation of amino acids formed during the hydrolysis of raw materials proteins (grains, fruits, potatoes), which leads to to the accumulation of higher alcohols in the production of ethyl alcohol, wines and beer;
• hydrolases- enzymes that catalyze the hydrolytic cleavage of bonds (peptide, glycosidic, ether, etc.). These include lipases that hydrolyze fats, peptidases - proteins, amylases and phosphorylases - starch, etc.;
• lyases- enzymes that catalyze the non-hydrolytic cleavage of groups from the substrate with the formation of a double bond and reverse reactions. For example, pyruvate decarboxylase removes CO2 from pyruvic acid, which leads to the formation of acetaldehyde as an intermediate product of alcoholic and lactic acid fermentations;
• isomerase- enzymes that catalyze the formation of substrate isomers by moving multiple bonds or groups of atoms within the molecule;
• ligases- enzymes that catalyze the addition of two molecules with the formation of new bonds.

Importance of enzymes. In the crude form, enzymes have been used since ancient times in the production of many food products (in bakery, alcohol industry, winemaking, cheese making, etc.). Consumer properties of a number of goods are largely formed in the process of a special operation - fermentation (black, red, yellow tea, cocoa beans, etc.). Purified enzymatic preparations began to be used in the 20th century. in the production of juices, pure amino acids for treatment and artificial nutrition, removal of lactose from milk for products baby food etc. During the storage of food products, enzymes contribute to the ripening of meat, fruits and vegetables, but they can also cause their deterioration (rotting, mold, sliming, fermentation).

Properties. Enzymes have a high catalytic activity, due to which a small amount of them can activate the biochemical processes of huge amounts of substrate; the specificity of the action, i.e. certain enzymes act on specific substances; reversibility of action (the same enzymes can carry out the breakdown and synthesis of certain substances); mobility, manifested in a change in activity under the influence various factors(temperature, humidity, pH of the medium, activators and inactivators).

Each of these properties is characterized by certain optimal ranges (for example, in the temperature range of 40-50 ° C, the highest activity of enzymes is noted). Any deviation from the optimal range causes a decrease in enzyme activity, and sometimes their complete inactivation (for example, high temperatures sterilization). Many methods of preserving food raw materials are based on this. In this case, there is a partial or complete inactivation of the own enzymes of raw materials and products, as well as microorganisms that cause their spoilage.

For the inactivation of enzymes of food raw materials and goods during storage, a variety of physical, physico-chemical, chemical, biochemical and combined methods are used.

Polyphenols - biopolymers, macromolecules of which may include phenolic acids, alcohols and their esters, as well as sugars and other compounds.

These substances are found in nature only in plant cells. In addition, they can be found in wood and wood products, peat, brown and hard coal, oil residues.

Polyphenols are most important in fresh fruits, vegetables and their processed products, including wines, liqueurs, as well as in tea, coffee, cognac, rum and beer. In these products, polyphenols affect the organoleptic properties (taste, color), physiological value (many of these substances have P-vitamin activity, bactericidal properties) and shelf life.

Polyphenols contained in products of plant origin include tannins (for example, catechins), as well as dyes (flavonoids, anthocyanins, melanins, etc.).

Classification of organic substances

Depending on the type of structure of the carbon chain, organic substances are divided into:

• acyclic and cyclic.
• marginal (saturated) and unsaturated (unsaturated).
• carbocyclic and heterocyclic.
• alicyclic and aromatic.

Acyclic compounds are organic compounds in whose molecules there are no cycles and all carbon atoms are connected to each other in straight or branched open chains.

In turn, among acyclic compounds, limiting (or saturated) compounds are distinguished, which contain only single carbon-carbon (C-C) bonds in the carbon skeleton and unsaturated (or unsaturated) compounds containing multiples - double (C \u003d C) or triple (C ≡ C) communications.

Cyclic compounds are chemical compounds in which there are three or more bonded atoms forming a ring.

Depending on which atoms the rings are formed, carbocyclic compounds and heterocyclic compounds are distinguished.

Carbocyclic compounds (or isocyclic) contain only carbon atoms in their cycles. These compounds are in turn divided into alicyclic compounds (aliphatic cyclic) and aromatic compounds.

Heterocyclic compounds contain one or more heteroatoms in the hydrocarbon cycle, most often oxygen, nitrogen, or sulfur atoms.

The simplest class of organic substances are hydrocarbons - compounds that are formed exclusively by carbon and hydrogen atoms, i.e. formally do not have functional groups.

Since hydrocarbons do not have functional groups, they can only be classified according to the type of carbon skeleton. Hydrocarbons, depending on the type of their carbon skeleton, are divided into subclasses:

1) Limiting acyclic hydrocarbons are called alkanes. The general molecular formula of alkanes is written as C n H 2n+2, where n is the number of carbon atoms in a hydrocarbon molecule. These compounds do not have interclass isomers.

2) Acyclic unsaturated hydrocarbons are divided into:

a) alkenes - they contain only one multiple, namely one double C \u003d C bond, the general formula of alkenes is C n H 2n,

b) alkynes - in alkyne molecules there is also only one multiple, namely triple C≡C bond. The general molecular formula of alkynes is C n H 2n-2

c) alkadienes - in the molecules of alkadienes there are two double C=C bonds. The general molecular formula of alkadienes is C n H 2n-2

3) Cyclic saturated hydrocarbons are called cycloalkanes and have the general molecular formula C n H 2n.

The rest of the organic matter organic chemistry are considered as derivatives of hydrocarbons formed by introducing so-called functional groups into hydrocarbon molecules that contain other chemical elements.

Thus, the formula of compounds with one functional group can be written as R-X, where R is a hydrocarbon radical, and X is a functional group. A hydrocarbon radical is a fragment of a hydrocarbon molecule without one or more hydrogen atoms.

According to the presence of certain functional groups, the compounds are divided into classes. The main functional groups and classes of compounds in which they are included are presented in the table:

Thus, various combinations types of carbon skeletons with different functional groups give big variety variants of organic compounds.

Halogen derivatives of hydrocarbons

Halogen derivatives of hydrocarbons are compounds obtained by replacing one or more hydrogen atoms in a molecule of any initial hydrocarbon with one or more atoms of a halogen, respectively.

Let some hydrocarbon have the formula C n H m, then when replacing in its molecule X hydrogen atoms on X halogen atoms, the formula for the halogen derivative will look like C n H m-X Hal X. Thus, monochlorine derivatives of alkanes have the formula C n H 2n+1 Cl, dichloro derivatives C n H 2n Cl 2 etc.

Alcohols and phenols

Alcohols are derivatives of hydrocarbons in which one or more hydrogen atoms are replaced by the hydroxyl group -OH. Alcohols with one hydroxyl group are called monatomic, with two - diatomic, with three triatomic etc. For example:

Alcohols with two or more hydroxyl groups are also called polyhydric alcohols. The general formula of limiting monohydric alcohols is C n H 2n+1 OH or C n H 2n+2 O. The general formula of limiting polyhydric alcohols is C n H 2n+2 O x, where x is the atomicity of the alcohol.

Alcohols can also be aromatic. For example:

The general formula of such monohydric aromatic alcohols is C n H 2n-6 O.

However, it should be clearly understood that derivatives of aromatic hydrocarbons in which one or more hydrogen atoms at the aromatic nucleus are replaced by hydroxyl groups do not apply to alcohols. They belong to the class phenols . For example, this given compound is an alcohol:

And this is phenol:

The reason why phenols are not classified as alcohols lies in their specific chemical properties, which greatly distinguish them from alcohols. It is easy to see that monohydric phenols are isomeric to monohydric aromatic alcohols, i.e. also have the general molecular formula C n H 2n-6 O.

Amines

Amines called ammonia derivatives in which one, two or all three hydrogen atoms are replaced by a hydrocarbon radical.

Amines in which only one hydrogen atom is replaced by a hydrocarbon radical, i.e. having the general formula R-NH 2 are called primary amines.

Amines in which two hydrogen atoms are replaced by hydrocarbon radicals are called secondary amines. The formula for a secondary amine can be written as R-NH-R'. In this case, the radicals R and R' can be either the same or different. For example:

If there are no hydrogen atoms at the nitrogen atom in amines, i.e. all three hydrogen atoms of the ammonia molecule are replaced by a hydrocarbon radical, then such amines are called tertiary amines. In general, the formula of a tertiary amine can be written as:

In this case, the radicals R, R', R'' can be either completely identical, or all three are different.

General molecular formula of primary, secondary and tertiary limit amines has the form C n H 2 n +3 N.

Aromatic amines with only one unsaturated substituent have the general formula C n H 2 n -5 N

Aldehydes and ketones

Aldehydes called derivatives of hydrocarbons, in which, at the primary carbon atom, two hydrogen atoms are replaced by one oxygen atom, i.e. derivatives of hydrocarbons in the structure of which there is an aldehyde group –CH=O. The general formula for aldehydes can be written as R-CH=O. For example:

Ketones called derivatives of hydrocarbons, in which two hydrogen atoms at the secondary carbon atom are replaced by an oxygen atom, i.e. compounds in the structure of which there is a carbonyl group -C (O) -.

The general formula for ketones can be written as R-C(O)-R'. In this case, the radicals R, R' can be either the same or different.

For example:

As you can see, aldehydes and ketones are very similar in structure, but they are still distinguished as classes, since they have significant differences in chemical properties.

The general molecular formula of saturated ketones and aldehydes is the same and has the form C n H 2 n O

carboxylic acids

carboxylic acids called derivatives of hydrocarbons in which there is a carboxyl group -COOH.

If an acid has two carboxyl groups, the acid is called dicarboxylic acid.

Limit monocarboxylic acids (with one -COOH group) have a general molecular formula of the form C n H 2 n O 2

Aromatic monocarboxylic acids have the general formula C n H 2 n -8 O 2

Ethers

Ethers - organic compounds in which two hydrocarbon radicals are indirectly connected through an oxygen atom, i.e. have a formula of the form R-O-R'. In this case, the radicals R and R' can be either the same or different.

For example:

The general formula of saturated ethers is the same as for saturated monohydric alcohols, i.e. C n H 2 n +1 OH or C n H 2 n +2 O.

Esters

Esters are a class of compounds based on organic carboxylic acids, in which the hydrogen atom in the hydroxyl group is replaced by the hydrocarbon radical R. The general form of esters can be written as:

For example:

Nitro compounds

Nitro compounds- derivatives of hydrocarbons, in which one or more hydrogen atoms are replaced by a nitro group -NO 2.

Limit nitro compounds with one nitro group have the general molecular formula C n H 2 n +1 NO 2

Amino acids

Compounds that simultaneously have two functional groups in their structure - amino NH 2 and carboxyl - COOH. For example,

NH 2 -CH 2 -COOH

Limiting amino acids with one carboxyl and one amino group are isomeric to the corresponding limiting nitro compounds i.e. like they have the general molecular formula C n H 2 n +1 NO 2

In the USE assignments for the classification of organic substances, it is important to be able to write down the general molecular formulas of homologous series different types compounds, knowing the structural features of the carbon skeleton and the presence of certain functional groups. To learn how to determine the general molecular formulas of organic compounds different classes, material on this topic will be useful.

Nomenclature of organic compounds

Features of the structure and chemical properties of compounds are reflected in the nomenclature. The main types of nomenclature are systematic and trivial.

Systematic nomenclature actually prescribes algorithms, according to which one or another name is compiled in strict accordance with the structural features of an organic substance molecule or, roughly speaking, its structural formula.

Consider the rules for naming organic compounds according to systematic nomenclature.

When naming organic substances according to systematic nomenclature, the most important thing is to correctly determine the number of carbon atoms in the longest carbon chain or count the number of carbon atoms in a cycle.

Depending on the number of carbon atoms in the main carbon chain, compounds will have a different root in their name:

The second important component taken into account when compiling names is the presence / absence of multiple bonds or a functional group, which are listed in the table above.

Let's try to give a name to a substance that has a structural formula:

1. The main (and only) carbon chain of this molecule contains 4 carbon atoms, so the name will contain the root but-;

2. There are no multiple bonds in the carbon skeleton, therefore, the suffix to be used after the root of the word will be -an, as for the corresponding saturated acyclic hydrocarbons (alkanes);

3. The presence of a functional group -OH, provided that there are no more senior functional groups, adds after the root and suffix from paragraph 2. another suffix - "ol";

4. In molecules containing multiple bonds or functional groups, the numbering of carbon atoms of the main chain starts from the side of the molecule to which they are closer.

Let's look at another example:

The presence of four carbon atoms in the main carbon chain tells us that the root “but-” is the basis of the name, and the absence of multiple bonds indicates the suffix “-an”, which will follow immediately after the root. The eldest group in this compound is carboxyl, which determines whether this substance belongs to the class of carboxylic acids. Therefore, the ending at the name will be "-ovoic acid". At the second carbon atom is an amino group NH2 -, therefore, this substance belongs to amino acids. Also at the third carbon atom we see the hydrocarbon radical methyl ( CH 3 -). Therefore, according to the systematic nomenclature, this compound is called 2-amino-3-methylbutanoic acid.

The trivial nomenclature, in contrast to the systematic one, as a rule, has no connection with the structure of the substance, but is mainly due to its origin, as well as chemical or physical properties.

Rice. 5. Friedrich Wöhler
(1800–1882)

Rice. 6. Alexander
Mikhailovich Butlerov
(1828–1886)

The essence of the theory of chemical structure they created can be formulated in the form of three propositions.
1. Atoms in molecules are connected in a certain order according to their valence, and carbon in organic compounds is tetravalent.
2. The properties of substances are determined not only by the qualitative and quantitative elemental composition, but also by the order of the bonds of atoms in molecules, i.e. chemical structure.
3. Atoms in molecules exert mutual influence on each other, which affects the properties of substances.
* German chemist. Conducted research in the field of inorganic and organic chemistry. Established the existence of the phenomenon of isomerism, for the first time carried out the synthesis of organic matter (urea) from inorganic. Received some metals (aluminum, beryllium, etc.).
** Outstanding Russian chemist, author of the theory of chemical
structure of organic matter. Based onconcepts of the structure explained the phenomenon of isomerism, predicted the existence of isomers of a number of substances and synthesized them for the first time. He was the first to synthesize a sugary substance. Founder of the School of Russian Chemistrykov, which included V.V. Markovnikov, A.M. Zaitsev, E.E. Wagner, A.E. Favorsky and others.

Today it seems incredible that until the middle of the 19th century, during the period of great discoveries in natural science, scientists had little idea internal organization substances. It was Butlerov who introduced the term "chemical structure", meaning by it a system of chemical bonds between atoms in a molecule, their mutual arrangement in space. Thanks to this understanding of the structure of the molecule, it became possible to explain the phenomenon of isomerism, predict the existence of unknown isomers, and correlate the properties of substances with their chemical structure. As an illustration of the phenomenon of isomerism, we present the formulas and properties of two substances - ethyl alcohol and dimethyl ether, which have the same elemental composition of C2H6O, but different chemical structures (Table 2).
table 2

Illustration of the dependence of the properties of a substancefrom its structure

The phenomenon of isomerism, which is very widespread in organic chemistry, is one of the reasons for the diversity of organic substances. Another reason for the diversity of organic substances is unique ability carbon atoms form chemical bonds with each other, resulting in carbon chains
different lengths and structures: unbranched, branched, closed. For example, four carbon atoms can form chains like this:

If we take into account that between two carbon atoms there can be not only simple (single) C–C bonds, but also double C=C and triple C≡C, then the number of variants of carbon chains and, consequently, various organic substances increases significantly.
The classification of organic substances is also based on Butlerov's theory of chemical structure. Depending on which atoms chemical elements are part of the molecule, all organic large groups: hydrocarbons, oxygen-containing, nitrogen-containing compounds.
Hydrocarbons are organic compounds that consist only of carbon and hydrogen atoms.
According to the structure of the carbon chain, the presence or absence of multiple bonds in it, all hydrocarbons are divided into several classes. These classes are shown in Figure 2.
If the hydrocarbon does not contain multiple bonds and the chain of carbon atoms is not closed, it belongs, as you know, to the class of saturated hydrocarbons, or alkanes. The root of this word is Arabic origin, and the suffix -an is present in the names of all hydrocarbons of this class.
Scheme 2

Hydrocarbon classification

The presence of one double bond in the hydrocarbon molecule makes it possible to attribute it to the class of alkenes, and its relation to this group of substances is emphasized
suffix -en in the name. The simplest alkene is ethylene, which has the formula CH2=CH2. There can be two C=C double bonds in a molecule, in which case the substance belongs to the class of alkadienes.
Try to explain the meaning of the suffixes -dienes yourself. For example, butadiene-1,3 has the structural formula: CH2=CH–CH=CH2.
Hydrocarbons with triple carbon-carbon bonds in the molecule are called alkynes. The suffix -in indicates belonging to this class of substances. The ancestor of the class of alkynes is acetylene (ethyne), the molecular formula of which is C2H2, and the structural formula is HC≡CH. From compounds with a closed carbon chain
atoms, the most important are arenas - a special class of hydrocarbons, the name of the first representative of which you probably heard - this is C6H6 benzene, the structural formula of which is also known to every cultured person:

As you already understood, in addition to carbon and hydrogen, the composition of organic substances can include atoms of other elements, primarily oxygen and nitrogen. Most often, the atoms of these elements in various combinations form groups that are called functional.
A functional group is a group of atoms that determines the most characteristic chemical properties of a substance and its belonging to a certain class of compounds.
The main classes of organic compounds containing functional groups are shown in Scheme 3.
Scheme 3
The main classes of organic substances containing functional groups

The functional group -OH is called hydroxyl and determines belonging to one of the most important classes of organic substances - alcohols.
The names of alcohols are formed using the suffix -ol. For example, the most famous representative of alcohols is ethyl alcohol, or ethanol, C2H5OH.
An oxygen atom can be bonded to a carbon atom by a double chemical bond. The >C=O group is called carbonyl. The carbonyl group is part of several
functional groups, including aldehyde and carboxyl. Organic compounds containing these functional groups are called aldehydes and carboxylic acids, respectively. Most famous representatives aldehydes are formaldehyde HSON and acetaldehyde CH3SON. With acetic acid CH3COOH, the solution of which is called table vinegar, everyone is probably familiar. A distinctive structural feature of nitrogen-containing organic compounds, and, first of all, amines and amino acids, is the presence of the –NH2 amino group in their molecules.
The above classification of organic substances is also very relative. Just as one molecule (for example, alkadienes) can contain two multiple bonds, a substance can be the owner of two or even more functional groups. So, the structural units of the main carriers of life on earth - protein molecules - are amino acids. The molecules of these substances necessarily contain at least two functional groups - a carboxyl and amino group. The simplest amino acid is called glycine and has the formula:

Like amphoteric hydroxides, amino acids combine the properties of acids (due to the carboxyl group) and bases (due to the presence of an amino group in the molecule).
For the organization of life on Earth, the amphoteric properties of amino acids are of particular importance - due to the interaction of amino groups and carboxyl groups of amino acids.
lots are linked into polymer chains of proteins.
? 1. What are the main provisions of the theory of the chemical structure of A.M. Butlerov. What role did this theory play in the development of organic chemistry?
2. What classes of hydrocarbons do you know? On what basis was this classification carried out?
3. What is called the functional group of an organic compound? What functional groups can you name? What classes of organic compounds contain these functional groups? Write down the general formulas of the classes of compounds and the formulas of their representatives.
4. Give a definition of isomerism, write down the formulas of possible isomers for compounds of composition C4H10O. Via various sources information, name each of them and prepare a report about one of the compounds.
5. Assign substances whose formulas are: C6H6, C2H6, C2H4, HCOOH, CH3OH, C6H12O6 to the corresponding classes of organic compounds. Using various sources of information, name each of them and prepare a report about one of the compounds.
6. Structural formula of glucose: To which class of organic compounds would you classify this substance? Why is it called a compound with a dual function?
7. Compare organic and inorganic amphoteric compounds.
8. Why are amino acids referred to as compounds with a dual function? What role does this structural feature of amino acids play in the organization of life on Earth?
9. Prepare a message on the topic “Amino acids are the “bricks” of life”, using the possibilities of the Internet.
10. Give examples of the relativity of dividing organic compounds into certain classes. Draw parallels of similar relativity for inorganic compounds.