Just like monosaccharides, are widely distributed in nature and disaccharides- known to all sucrose(cane or beet sugar), lactose(milk sugar), maltose(malt sugar).
The term "disaccharide" itself tells us about two monosaccharide residues interconnected in the molecules of these organic compounds, which can be obtained by hydrolysis (decomposition with water) of the disaccharide molecule.
disaccharides- carbohydrates, the molecules of which consist of two monosaccharide residues, which are connected to each other due to the interaction of two hydroxyl groups.
In the process of formation of a disaccharide molecule, one molecule of water is split off:
or for sucrose:
Therefore, the molecular formula of disaccharides is C 12 H 22 O 11.
The formation of sucrose occurs in plant cells under the influence of enzymes. But chemists have found a way to implement many of the reactions that are part of the processes that occur in wildlife. In 1953, the French chemist R. Lemieux for the first time carried out the synthesis of sucrose, which was called by his contemporaries "the conquest of the Everest of organic chemistry."
In industry, sucrose is obtained from sugar cane juice (content 14-16%), sugar beet (16-21%), as well as some other plants, such as Canadian maple or ground pear.
Everyone knows that sucrose is a crystalline substance that has a sweet taste and is highly soluble in water.
Sugar cane juice contains the carbohydrate sucrose, commonly referred to as sugar.
The name of the German chemist and metallurgist A. Marggraf is closely associated with the production of sugar from beets. He was one of the first researchers to use a microscope in his chemical studies, with which he discovered sugar crystals in beet juice in 1747.
Lactose - crystalline milk sugar, was obtained from the milk of mammals as early as the 17th century. Lactose is a less sweet disaccharide than sucrose.
Now let's get acquainted with carbohydrates that have a more complex structure - polysaccharides.
Polysaccharides- high-molecular carbohydrates, the molecules of which consist of many monosaccharides.
In a simplified form, the general scheme can be represented as follows:
Now let's compare the structure and properties of starch and cellulose - the most important representatives of polysaccharides.
The structural unit of the polymer chains of these polysaccharides, the formula of which is (C 6 H 10 O 5) n, are glucose residues. In order to write down the composition of the structural unit (C 6 H 10 O 5), you need to subtract a water molecule from the glucose formula.
Cellulose and starch are of vegetable origin. They are formed from glucose molecules as a result of polycondensation.
The equation for the polycondensation reaction, as well as the inverse process of hydrolysis for polysaccharides, can be conditionally written as follows:
Starch molecules can have both a linear and branched type of structure, cellulose molecules can only have a linear one.
When interacting with iodine, starch, unlike cellulose, gives a blue color.
These polysaccharides also have various functions in the plant cell. Starch serves as a reserve nutrient, cellulose performs a structural, building function. Plant cell walls are made up of cellulose.
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Classification
1) by the number of monosaccharide residues:
oligosaccharides - contain several monosaccharide residues;
Higher polysaccharides - contain many monosaccharide residues.
2) according to the structure of monosaccharide residues:
homopolysaccharides - consist of residues of one monosaccharide;
heteropolysaccharides - consist of residues of various monosaccharides.
disaccharides
Disaccharides are compounds consisting of two monosaccharide residues linked glycosidic bond.
Glycosidic bond formed by the interaction of two hydroxyl groups. If one of these hydroxyls is glycosidic, and the second is alcohol, then such a disaccharide is called regenerating. If both hydroxyls are glycosidic, then such a disaccharide is called non-restoring.
Reducing disaccharides
Maltose
Malt sugar. It is formed during the hydrolysis of starch by malt enzymes, as well as by amylases contained in saliva and in pancreatic juice (starch digestion).
The maltose molecule consists of two D-glucopyranose residues connected by an α-(1→4)-glycosidic bond.
Maltose restores Fehling's reagent, its solutions mutate:
Cellobiose
Formed by incomplete hydrolysis of celludose. Unlike maltose, cellobiose is not broken down by gastrointestinal enzymes, is not digested and is not absorbed by the body.
The cellobiose molecule consists of two D-glucopyranose residues connected by a β-(1→4)-glycosidic bond.
Cellobiose, like maltose, reduces Fehling's reagent and its solutions mutarotate:
Milk sugar is found in all types of milk in an amount of up to 4% (in women's milk - 8%). Lactose is broken down by lactase, an enzyme in the intestinal juice, and is a nutritious food, especially for infants. In pharmacy, lactose is used in the manufacture of powders and tablets.
Lactose is a heterodisaccharide. Its molecule consists of D-galactopyranose and D-glucopyranose residues linked by a β-(1→4)-glycosidic bond.
Non-reducing disaccharides
sucrose
Beet, cane sugar. It is found in the juices of many plants and fruits. Sucrose is broken down by sucrase, an enzyme in the intestinal juice, and is a nutritious product.
Carbohydrates - organic compounds, most often of natural origin, consisting only of carbon, hydrogen and oxygen.
Carbohydrates play a huge role in the life of all living organisms.
This class of organic compounds got its name because the first carbohydrates studied by man had a general formula of the form C x (H 2 O) y. Those. they were conditionally considered compounds of carbon and water. However, later it turned out that the composition of some carbohydrates deviates from this formula. For example, a carbohydrate such as deoxyribose has the formula C 5 H 10 O 4 . At the same time, there are some compounds that formally correspond to the formula C x (H 2 O) y, but are not related to carbohydrates, such as formaldehyde (CH 2 O) and acetic acid (C 2 H 4 O 2).
Nevertheless, the term "carbohydrates" has historically been assigned to this class of compounds, and therefore is widely used in our time.
Depending on the ability of carbohydrates to break down during hydrolysis into other carbohydrates with a lower molecular weight, they are divided into simple (monosaccharides) and complex (disaccharides, oligosaccharides, polysaccharides).
As you might guess, from simple carbohydrates, i.e. monosaccharides, carbohydrates with an even lower molecular weight cannot be obtained by hydrolysis.
Hydrolysis of one disaccharide molecule produces two monosaccharide molecules, and complete hydrolysis of one molecule of any polysaccharide produces many monosaccharide molecules.
The most common monosaccharides are glucose and fructose, which have the following structural formulas:
As you can see, both in the glucose molecule and in the fructose molecule there are 5 hydroxyl groups each, and therefore they can be considered polyhydric alcohols.
The glucose molecule contains an aldehyde group, i.e. in fact, glucose is a polyhydric aldehyde alcohol.
In the case of fructose, a ketone group can be found in its molecule, i.e. fructose is a polyhydric ketoalcohol.
All monosaccharides can react in the presence of hydrogen catalysts. In this case, the carbonyl group is reduced to an alcohol hydroxyl group. So, in particular, by hydrogenation of glucose in industry, an artificial sweetener is obtained - hexaatomic alcohol sorbitol:
The glucose molecule contains an aldehyde group in its composition, and therefore it is logical to assume that its aqueous solutions give qualitative reactions to aldehydes. Indeed, when an aqueous solution of glucose is heated with freshly precipitated copper (II) hydroxide, just as in the case of any other aldehyde, a brick-red precipitate of copper (I) oxide is observed from the solution. In this case, the aldehyde group of glucose is oxidized to carboxylic acid - gluconic acid is formed:
Glucose also enters into the “silver mirror” reaction when it is exposed to an ammonia solution of silver oxide. However, unlike the previous reaction, instead of gluconic acid, its salt is formed - ammonium gluconate, because. dissolved ammonia is present in the solution:
Fructose and other monosaccharides, which are polyhydric ketoalcohols, do not enter into qualitative reactions to aldehydes.
Since monosaccharides, including glucose and fructose, have several hydroxyl groups in their molecules. All of them give a qualitative reaction to polyhydric alcohols. In particular, freshly precipitated copper (II) hydroxide dissolves in aqueous solutions of monosaccharides. In this case, instead of a blue precipitate of Cu(OH) 2, a dark blue solution of complex copper compounds is formed.
Under the action of certain enzymes on glucose, glucose is able to turn into ethyl alcohol and carbon dioxide:
In addition to the alcoholic type of fermentation, there are also many others. For example, lactic acid fermentation, which occurs during the souring of milk, sauerkraut and cucumbers:
Monosaccharides exist in aqueous solution in three forms - two cyclic (alpha and beta) and one non-cyclic (normal). For example, in a glucose solution, the following equilibrium exists:
As can be seen, there is no aldehyde group in the cyclic forms, due to the fact that it participates in the formation of the cycle. On its basis, a new hydroxyl group is formed, which is called acetal hydroxyl. Similar transitions between cyclic and non-cyclic forms are observed for all other monosaccharides.
Disaccharides are called carbohydrates, the molecules of which consist of two monosaccharide residues linked together by the condensation of two hemiacetal hydroxyls or one alcohol hydroxyl and one hemiacetal. The bonds formed in this way between monosaccharide residues are called glycosidic bonds. The formula for most disaccharides can be written as C 12 H 22 O 11 .
The most common disaccharide is the familiar sugar, called by chemists sucrose . The molecule of this carbohydrate is formed by cyclic residues of one molecule of glucose and one molecule of fructose. The bond between disaccharide residues in this case is realized due to the elimination of water from two hemiacetal hydroxyls:
Since the bond between monosaccharide residues is formed by the condensation of two acetal hydroxyls, it is impossible for a sugar molecule to open any of the cycles, i.e. transition to the carbonyl form is impossible. In this regard, sucrose is not able to give qualitative reactions to aldehydes.
Disaccharides of this kind, which do not give a qualitative reaction to aldehydes, are called non-reducing sugars.
However, there are disaccharides that give qualitative reactions to the aldehyde group. This situation is possible when the hemiacetal hydroxyl from the aldehyde group of one of the initial monosaccharide molecules remains in the disaccharide molecule.
In particular, maltose reacts with an ammonia solution of silver oxide, as well as copper (II) hydroxide, like aldehydes. This is due to the fact that in its aqueous solutions there is the following equilibrium:
As can be seen, maltose exists in aqueous solutions in the form of two forms - with two cycles in the molecule and one cycle in the molecule and an aldehyde group. For this reason, maltose, unlike sucrose, gives a qualitative reaction to aldehydes.
All disaccharides are able to enter into a hydrolysis reaction catalyzed by acids, as well as by various enzymes. In the course of such a reaction, two monosaccharide molecules are formed from one molecule of the initial disaccharide, which can be either the same or different depending on the composition of the initial monosaccharide.
So, for example, the hydrolysis of sucrose leads to the formation of glucose and fructose in equal amounts:
And when maltose is hydrolyzed, only glucose is formed:
Disaccharides, being polyhydric alcohols, give the corresponding qualitative reaction with copper (II) hydroxide, i.e. when their aqueous solution is added to freshly precipitated copper (II) hydroxide, the water-insoluble blue precipitate of Cu(OH) 2 dissolves to form a dark blue solution.
Polysaccharides - complex carbohydrates, the molecules of which consist of a large number of monosaccharide residues linked by glycosidic bonds.
There is another definition of polysaccharides:
Polysaccharides called complex carbohydrates, the molecules of which form a large number of monosaccharide molecules during complete hydrolysis.
In general, the formula of polysaccharides can be written as (C 6 H 10 O 5) n .
Starch - a substance that is a white amorphous powder, insoluble in cold water and partially soluble in hot water to form a colloidal solution, commonly called starch paste.
Starch is formed from carbon dioxide and water during photosynthesis in the green parts of plants under the influence of sunlight energy. The largest amounts of starch are found in potato tubers, wheat, rice and corn grains. For this reason, these sources of starch are the raw material for its production in industry.
Cellulose - a substance in its pure state, which is a white powder, insoluble in either cold or hot water. Unlike starch, cellulose does not form a paste. Almost pure cellulose consists of filter paper, cotton wool, poplar fluff. Both starch and cellulose are plant products. However, the roles they play in plant life are different. Cellulose is mainly a building material, in particular, it is mainly formed by the shells of plant cells. Starch, on the other hand, carries mainly a storage, energy function.
All polysaccharides, including starch and cellulose, when completely burned in oxygen, form carbon dioxide and water:
With complete hydrolysis of both starch and cellulose, the same monosaccharide, glucose, is formed:
When iodine acts on anything that contains starch, a blue color appears. The blue color disappears on heating and reappears on cooling.
During the dry distillation of cellulose, in particular wood, its partial decomposition occurs with the formation of such low molecular weight products as methyl alcohol, acetic acid, acetone, etc.
Since both starch molecules and cellulose molecules contain alcohol hydroxyl groups, these compounds are able to enter into esterification reactions with both organic and inorganic acids.
Oligosaccharides - carbohydrates, the molecules of which contain from 2 to 10 monosaccharide residues connected by glycosidic bonds. In accordance with this, disaccharides, trisaccharides, etc. are distinguished. disaccharides - complex sugars, each molecule of which, during hydrolysis, breaks down into two molecules of monosaccharides. Disaccharides, along with polysaccharides, are one of the main sources of carbohydrates in human and animal food. By structure, disaccharides are glycosides in which 2 monosaccharide molecules are connected by a glycosidic bond. The most widely known disaccharides are maltose, lactose and sucrose. Maltose, which is α-glucopyranosyl-(1–>4)-α-glucopyranose, is formed as an intermediate product by the action of amylases on starch (or glycogen), contains 2 α-D-glucose residues (the name of the sugar whose hemiacetal hydroxyl is involved in the formation glycosidic bond, ends in ≪yl≫).
Maltose
In the maltose molecule, the second glucose residue has a free hemiacetal hydroxyl. Such disaccharides have reducing properties. One of the most common disaccharides is sucrose, a common food sugar. The sucrose molecule consists of one D-glucose and one D-fructose residue. Therefore, it is α-gluco-pyranosyl-(1->2)-β-fructofuranoside:
sucrose
Unlike most disaccharides, sucrose does not have a free hemiacetal hydroxyl and does not have reducing properties. Hydrolysis of sucrose leads to the formation of a mixture, which is called invert sugar. This mixture is dominated by strongly levorotatory fructose, which inverts (reverses) the sign of rotation of the dextrorotatory solution of the original sucrose. The disaccharide lactose is found only in milk and consists of D-galactose and D-glucose. This is β-galactopyranosyl-(1->4)-glucopyranose:
Due to the presence of free hemiacetal hydroxyl (in glucose residue) in the molecule, lactose is one of the reducing disaccharides. Among the natural trisaccharides, raffinose is the best known, containing fructose, glucose, and galactose residues. Raffinose is found in large quantities in sugar beet and in many other plants. In general, the oligosaccharides present in plant tissues are more diverse in their composition than the oligosaccharides of animal tissues.
Chondroitin sulfates - components of heart valves, nasal septum, cartilage tissues. M.b. several types. Handroitin - 4-sulfate and 6-sulfate. The heteropolysaccharide consists of repeating disaccharide units β(D)-glucuranosyl-1,3-β(D,N)-acetylgalactosamine. Sulfate at positions 4 and 6.
Glaluronic acid - is contained in the connective, integumentary tissues, is part of the vitreous body of the eye. Viscous in-in, well protects the eye bones from external influences. During hydrolysis, it forms glucuronic acid and N-acetylglucosamine. Communication 1,3-β-glycosidic.
Heparin -contained in the liver, in the spleen, a strong anticoagulant, prevents blood from clotting (1 mg of heparin prevents 500 ml from clotting), is present on the surface of many cells and inside cells.
In medical practice, it is used to treat thrombosis, burns, and during blood transfusion as a stabilizer.
The composition includes repeating units of 6 sugar residues N-acetylglucosamine, its sulfo derivative, non-acetylated derivative.
Homopolysaccharides(starch, cellulose, pectin and others)
Hydrolysis gives glucose
Starch digested by amylase (1,4-glycosidase), which cleaves α-1,4-glycosidic bonds.
Starch consists of amylose (linear structure and amylopectin) branched structure, but every 25 fragments.
All starches differ in the amount of amylose amylopectin.
During acid hydrolysis, starch is broken down into dextrins (red color). Coloring with iodine indicates splitting. If the color is pale, then the splitting is greater.
Glycogen reminiscent of amylopectin (splitting for every 10-12 bonds) in the liver, in the muscles, reserve nutrition.
Cellulose has a 1,4-β-glycosidic bond.
Pectin to-you - polysaccharides of fruits, fruits, vegetables, are methyl esters of galacturonic acid, 1,4-α-glycosidic bond.
Glycosides - derivatives of hydrocarbons by glycosidic hydrolysis.
Amygdalin - is part of the almond. Glucoses linked together by 1,6-β-glycosidic bonds.
Glycovanillin (glucose, β glycosidic bond).
Sinigrin (included in mustard).
Neuraminic acid - a condensation product of pyruvic acid and N-acetylmonosamine. Included in gangmosides (in lipids).
Muranoic acid (included in the walls of bacteria).
Tannins - vegetable origin. Soluble in water, give colored solutions with ferric chloride. They are divided into 2 types: hydrolyzable and non-hydrolyzable (condense when T with acid).
Itype - fineness - derivatives of glucose and di-trimers of gallic acids.
(gallic acid 
, capable of forming dioxides)
Tones can be different:
Fischer's tonin has the structure:
DG - digalic acid
G - gallic acid
The exact structure of natural tannins has not been established.
Used: in medicine, pharmacy, for the isolation of alkaloid reagents.
Mr m.b. up to 3000, contained in the bark of trees, in the fruits of some plants.
Exists ellag oak , characterized in that during hydrolysis they form an insoluble ellagic acid.
Type II - kapihinn(condensable tannins).
F 
ravonoids: compounds: leucoanthocyanin, catechin, flavonone, flavonol, flavon, anticyan.
catechin contain in A and B OH-, CH2- and differ in them. They do not form glycosides in nature. Easily oxidized and capable of polymerization, crystalline colorless in-va. Contained in the fruits of apple trees, cherries, pears, in the leaves of the shoots of the tea tree.
The enzymatic process leads to dimerization. He studies winemaking, tea industry, cocoa production.
Compounds - flavonoids have vitamin capacity (P). They increase the elasticity of blood capillaries, most of all inherent in catechin.
V 
vitamin P - quartzetyl glycoside
Quarcetil– aglycone 6β(α)-rhamnoside-(D)-glucose-rhamnose. Communication due to 6 carbon atoms in glucose. In the absence of rutin in food, the capillaries become permeable -> purple disease.
Anthocyanins- coloring in-va plants (dilfinidin, piporgonidin, cyanidin (rose and cornflower)). They differ in radicals. They exist in the form of glucosides.
Disaccharides - These are sugar-like complex carbohydrates, the molecules of which, upon hydrolysis, break down into two molecules of monosaccharides. Molecular formula C 12 H 22 O 11. Disaccharides are found in products of natural origin: sucrose (beet sugar) in large quantities, up to 28%, in sugar beets; lactose (milk sugar) - in milk; trehalose (mushroom sugar) - in mushrooms; maltose (malt sugar) is formed by partial hydrolysis of starch, etc.
By their structure, disaccharides are glycosides. Depending on which hydroxyl of the second monosaccharide is involved in the formation of a bond with the first monosaccharide, two types of disaccharides are distinguished: reducing (reducing); non-restoring.
Reducing disaccharides called glycosyl-glycoses; the bond between monosaccharide molecules in these disaccharides is formed due to the hemiacetal hydroxyl of one molecule and the alcohol hydroxyl (most often at the fourth carbon atom) of the second molecule. The most important representatives: maltose, lactose, cellobiose. In solution, they are in tautomeric forms: cyclic (hemiacetal) and hydroxycarbonyl (aldehyde).
lactose lactose
Structure. The composition of disaccharides may include two identical or different monosaccharides in hemiacetal (cyclic) form.
Thus, a maltose molecule (malt sugar) consists of two molecules of α-D-glucose in the pyranose form, linked by an l-4-α-glycosidic bond.
The second monosaccharide residue of the maltose molecule retains the free hemiacetal hydroxyl. For this reason, maltose can exist in solution in tautomeric forms: cyclic and hydroxycarbonyl, which are in dynamic equilibrium with each other.
maltose maltose
(hemiacetal form) (hydroxycarbonyl form)
All reducing disaccharides (lactose, cellobiose, etc.) are built on this principle.
Properties of reducing (reducing) disaccharides. Reducing disaccharides are crystalline substances that are highly soluble in water, have a sweet taste, and are hygroscopic. Solutions of these disaccharides are neutral and have optical activity. Chemically, reducing disaccharides exhibit the properties of aldehydes: they give a silver mirror reaction, reduce Fehling's liquid, react with reagents for a carbonyl group (with phenylhydrazine, hydroxylamine). Due to the hemiacetal hydroxyl, disaccharides form glycosides, and also exhibit the properties of polyhydric alcohols: they enter into alkylation, acylation reactions, give a qualitative reaction to polyhydric alcohols (dissolve Cu (OH) 2).
maltose (aldehyde form) maltobionic acid
This group of disaccharides is able to reduce Ag + to Ag 0 in the silver mirror reaction, Cu 2+ to Cu + in the reaction with Fehling's solution, which is why they are called reducing disaccharides. Like all complex carbohydrates, disaccharides can be hydrolyzed by mineral acids or enzymes.
C 12 H 22 O 11 + H 2 O 
2C 6 H 12 O 6
maltose glucose
Non-reducing disaccharides called glycosyl glycosides; the bond between monosaccharides in these disaccharides is formed with the participation of both hemiacetal hydroxyls, so they cannot be converted into other tautomeric forms. Their most important representatives are sucrose and trehalose.
trehalose sucrose
The trehalose molecule consists of two α-D-glucopyranose residues, the sucrose molecule consists of an α-D-glucopyranose residue and a β-D-fructofuranose residue. Since in disaccharides of this group, the bond between monosaccharides is carried out due to both hemiacetal hydroxyls, they cannot tautomerically pass into the oxycarbonyl form, therefore, they cannot give reactions to the carbonyl group, including the aldehyde group (they do not give a silver mirror reaction, do not react with Fehling's solution). Such disaccharides are not capable of exhibiting reducing properties, therefore they are called non-reducing disaccharides. They exhibit the properties of polyhydric alcohols (dissolve copper hydroxide, enter into alkylation and acylation reactions), as all complex carbohydrates are hydrolyzed in the presence of mineral acids or under the action of enzymes.
The structure and properties of sucrose. Sucrose (beet sugar) is one of the oldest foodstuffs known to man. Sucrose was originally isolated from sugar cane and then from sugar beets. Sucrose is also found in many other plants (corn, maple, palm, etc.).
Molecular composition of sucrose C 12 H 22 O 11.
The sucrose molecule consists of two monosaccharides: glucose in the α-D-pyranose form and fructose in the β-D-furanose form, interconnected by a 1-2-glycosidic bond involving two hemiacetal (glycosidic) hydroxyls. There are no free hemiacetal hydroxyls in the sucrose molecule, so it cannot tautomerically transform into the hydroxycarbonyl form.
When heated above 160 ° C, sucrose partially decomposes, releasing water and turning into a brown mass - caramel.
An aqueous solution of sucrose dissolves copper hydroxide, forming a solution of copper sucrose, while exhibiting the properties of polyhydric alcohols. When a sucrose solution is heated in the presence of mineral acids, sucrose is hydrolyzed, resulting in a mixture of glucose and fructose in equal amounts (artificial honey). The process of hydrolysis of sucrose is called inversion, since in this case there is a change in the right rotation of the solution to the left.
Sucrose is widely used as a food product, in the production of confectionery, bakery products, jams, compotes, jams, etc. In pharmacology, it is used to prepare syrups, mixtures, powders, etc.
Esters of sucrose and higher fatty acids have high detergency and are used as industrial detergents. These products are odorless, completely non-poisonous and completely destroyed by bacteria during the biological self-purification of water.
Diesters of higher fatty acids and sucrose are used as emulsifiers in the production of margarine, drugs and cosmetics.
Octamethylsucrose is used in the plastics industry as a plasticizer.
Sucrose octaacetate is used as an intermediate layer in the production of triplex glass.
Sugar production waste (molasses) is used for the production of ethyl alcohol and in the confectionery industry.
