Examples of monosaccharides disaccharides polysaccharides. Monosaccharides, disaccharides, polysaccharides: carbohydrates in examples. Chemical properties of starch and cellulose
20. Reducing disaccharides (maltose, lactose): structure, biochemical transformations (oxidation, reduction).
Reducing disaccharides. In these disaccharides, one of the monosaccharide residues is involved in the formation of a glycosidic bond due to the hydroxyl group, most often at C-4 or C-6, less often at C-3. The disaccharide has a free hemiacetal hydroxyl group, as a result of which the ability to open the ring is retained. The reducing properties of such disaccharides and the mutarotation of their freshly prepared solutions are due to the possibility of cyclo-oxo-tautomerism. Representatives of reducing disaccharides are maltose, cellobiose, lactose.
maltose (trivial name xmal sugar)" - product of enzymatic hydrolysis starch.
In this disaccharide, monosaccharide residues are linked by a glycoside-glycose bond (a-1,4-bond).
Due to the presence of a hemiacetal function in the maltose molecule, the a-anomer is in equilibrium with the p-anomer - p-maltose, 4-0-(a-D-glucopyranosyl)-p-0-glucopyranose. If it is subjected to acid hydrolysis, 2 moles of 0-(+)-glucose are obtained.
In contrast to sucrose, maltose is a reducing glycoside, since its structure contains a hemiacetal fragment. Maltose gives reactions with the Benedict-Fehling reagent and phenylhydrazine.
Maltose is a reducing sugar because it has an unsubstituted hemiacetal hydroxyl group. When maltose is boiled with dilute acid and under the action of the enzyme, maltase is hydrolyzed (two molecules of glucose C6H12O6 are formed).
Maltose contains a free glycosidic hydroxyl near the C-1-carbon atom, therefore it has reducing properties characteristic of reducing mono- and disaccharides. In solutions, maltose can exist in two forms - cyclic and aldehyde, which are in dynamic equilibrium. When maltose is hydrolyzed by the enzyme maltase, two molecules of alpha-D-glucose are formed. When the aldehyde group of maltose is oxidized, maltobionic acid is formed.
Other examples of disaccharides include lactose (milk sugar) - a disaccharide containing a p-D-galactopyranose residue (in a fixed (3-form) and D-glucose and present in the milk of almost all mammals:
Hydrolysis of sucrose in the presence of mineral acids (H 2 SO 4, Hcl, H 2 CO 3):
Oxidation of maltose (reducing disaccharide), such as the "silver mirror" reaction:
21. Non-reducing disaccharides (sucrose): structure, inversion, application.
Sucrose is a disaccharide consisting of D-glucose and D-fructose residues linked by a glycosidic-glycosidic bond (a-1,-2-bond).
Sucrose is a non-reducing disaccharide (see Oligosaccharides), a widespread reserve in plants, formed during photosynthesis and stored in leaves, stems, roots, flowers or fruits. When loading above the melting temperature, decomposition and coloring of the melt (caramelization) occur. Sucrose does not reduce the Fehling reagent, it is quite stable to alkalis, but, being ketofuranoside, it is extremely easily (~ 500 times faster than trehalose or maltose) split (hydrolyzed) by acids into D-glucose and D-fructose. Hydrolysis of sucrose is accompanied by a change in the sign of beats. rotation of the solution and therefore called inversion.
A similar hydrolysis proceeds under the action of a-glucosidase (maltase) or b-fructofuranosidase (invertase). Sucrose is easily fermented by yeast. Being weak to-one (K approx. 10-13), sucrose forms complexes (saccharates) with hydroxides of alkali and alkaline earth metals, to-rye regenerate sucrose under the action of CO2.
The biosynthesis of sucrose occurs in the vast majority of photosynthetic eukaryotes, DOS. the mass of to-rykh is made up of plants (with the exception of representatives of red, brown, as well as diatoms and some other unicellular algae); its key stage is on loan. uridine diphosphate glucose and 6-phosphate-D-fructose. Animals are not capable of biosynthesis of sucrose.
Sucrose inversion. Acid hydrolysis of (+) sucrose or the action of invertase produces equal amounts of D (+) glucose and D (-) fructose. Hydrolysis is accompanied by a change in the sign of the specific rotation angle [α] from positive to negative, so the process is called inversion, and the mixture of D(+)glucose and D(-)fructose is called invert sugar.
Sucrose is obtained in prom. scales from the juice of sugar cane Saccharum officinarum or sugar beet Beta vulgaris; these two plants provide approx. 90% of the world's sucrose production (in a ratio of approx. 2:1), which exceeds 50 million tons / year. Chem. the synthesis of sucrose is very complex and economical. doesn't matter.
Sucrose is used as food. product (sugar) directly or as part of confectionery, and in high concentrations as a preservative; sucrose also serves as a substrate in prom. fermentation processes for obtaining ethanol, butanol, glycerin, citric and levulinic acid, dextran; also used in the preparation of lek. Wed-in; certain esters of sucrose with higher fatty acids are used as non-ionic detergents.
For qualities. detection of sucrose, blue staining with an alkaline solution of diazouracil can be used, a cut, however, also gives higher oligosaccharides containing a sucrose fragment in the molecule, raffinose, gentianose, stachyose.
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One of the varieties of organic compounds necessary for the full functioning of the human body are carbohydrates.
They are divided into several types according to their structure - monosaccharides, disaccharides and polysaccharides. It is necessary to understand what they are for and what their chemical and physical properties are.
Carbohydrates are compounds that contain carbon, hydrogen and oxygen. Most often they are of natural origin, although some are created industrially. Their role in the life of living organisms is enormous.
Their main functions are as follows:
- Energy. These compounds are the main source of energy. Most of the organs can fully work due to the energy obtained from the oxidation of glucose.
- Structural. Carbohydrates are necessary for the formation of almost all body cells. Fiber plays the role of a supporting material, and complex carbohydrates are found in bones and cartilage. One of the components of cell membranes is hyaluronic acid. Also, carbohydrate compounds are required in the process of enzyme production.
- Protective. During the functioning of the body, the work of the glands is carried out, which secrete secretory fluids necessary to protect the internal organs from pathogenic effects. A significant part of these liquids is represented by carbohydrates.
- Regulatory. This function is manifested in the effect on the human body of glucose (maintains homeostasis, controls osmotic pressure) and fiber (affects gastrointestinal motility).
- Special Features. They are characteristic of certain types of carbohydrates. These special functions include: participation in the process of transmission of nerve impulses, the formation of different blood groups, etc.
Based on the fact that the functions of carbohydrates are quite diverse, it can be assumed that these compounds should differ in their structure and characteristics.
This is true, and their main classification includes such varieties as:
- . They are considered the simplest. The remaining types of carbohydrates enter the process of hydrolysis and break down into smaller components. Monosaccharides do not have this ability, they are the final product.
- disaccharides. In some classifications, they are referred to as oligosaccharides. They contain two monosaccharide molecules. It is on them that the disaccharide is divided during hydrolysis.
- Oligosaccharides. This compound contains from 2 to 10 molecules of monosaccharides.
- Polysaccharides. These compounds are the largest variety. They contain more than 10 molecules of monosaccharides.
Each type of carbohydrate has its own characteristics. You need to consider them in order to understand how each of them affects the human body and what are its benefits.
These compounds are the simplest form of carbohydrates. They contain one molecule, therefore, during hydrolysis, they do not divide into small blocks. Monosaccharides combine to form disaccharides, oligosaccharides, and polysaccharides.
They are distinguished by a solid state of aggregation and a sweet taste. They have the ability to dissolve in water. They can also dissolve in alcohols (the reaction is weaker than with water). Monosaccharides almost do not react to mixing with esters.
Natural monosaccharides are most often mentioned. Some of them people consume with food. These include glucose, fructose and galactose.
- chocolate;
- fruit;
- some types of wine;
- syrups, etc.
The main function of carbohydrates of this type is energy. It cannot be said that the body cannot do without them, but they have properties that are important for the full functioning of the body, for example, participation in metabolic processes.
Monosaccharides are absorbed by the body faster than anything that happens in the digestive tract. The process of assimilation of complex carbohydrates, unlike simple compounds, is not so simple. First, complex compounds must be divided into monosaccharides, only after that they are absorbed.
It is one of the common types of monosaccharides. It is a white crystalline substance that is formed naturally - during photosynthesis or during hydrolysis. The compound formula is C6H12O6. The substance is highly soluble in water, has a sweet taste.
Glucose provides the cells of muscle and brain tissue with energy. When ingested, the substance is absorbed, enters the bloodstream and spreads throughout the body. There it is oxidized with the release of energy. This is the main source of energy supply for the brain.
With a lack of glucose in the body, hypoglycemia develops, which primarily affects the functioning of brain structures. However, its excessive content in the blood is also dangerous, as it leads to the development of diabetes. Also, when a large amount of glucose is consumed, body weight begins to increase.
Fructose
It belongs to the group of monosaccharides and is very similar to glucose. Differs in slower rates of assimilation. This is because fructose must first be converted to glucose in order to be absorbed.
Therefore, this compound is considered harmless for diabetics, since its consumption does not lead to a sharp change in the amount of sugar in the blood. However, this diagnosis still requires caution.
Fructose has the ability to quickly convert to fatty acids, which causes obesity. It also reduces insulin sensitivity, which causes type 2 diabetes.
This substance can be obtained from berries and fruits, and also from honey. Usually it is there in combination with glucose. The compound also has a white color. The taste is sweet, and this feature is more intense than in the case of glucose.
Other connections
There are other monosaccharide compounds. They can be natural or semi-artificial.
The natural one is galactose. It is also found in foods, but is not found in its pure form. Galactose is the result of the hydrolysis of lactose. Its main source is called milk.
Other natural monosaccharides are ribose, deoxyribose, and mannose.
There are also varieties of such carbohydrates, for which industrial technologies are used.
These substances are also found in food and enter the human body:
- rhamnose;
- erythrulose;
- ribulose;
- D-xylose;
- L-allose;
- D-sorbose, etc.
Each of these compounds has its own characteristics and functions.
Disaccharides and their uses
The next type of carbohydrate compounds are disaccharides. They are considered complex substances. As a result of hydrolysis, two molecules of monosaccharides are formed from them.
This type of carbohydrate has the following features:
- hardness;
- solubility in water;
- poor solubility in concentrated alcohols;
- sweet taste;
- color - from white to brown.
The main chemical properties of disaccharides are hydrolysis reactions (breaking of glycosidic bonds and the formation of monosaccharides) and condensation (polysaccharides are formed).
There are 2 types of such compounds:
- Restorative. Their feature is the presence of a free hemiacetal hydroxyl group. Due to it, such substances have reducing properties. This group of carbohydrates includes cellobiose, maltose and lactose.
- Non-reducing. These compounds are not reducible because they lack a hemiacetal hydroxyl group. The best known substances of this type are sucrose and trehalose.
These compounds are widely distributed in nature. They can occur both in free form and as part of other compounds. Disaccharides are a source of energy, as glucose is formed from them during hydrolysis.
Lactose is very important for children because it is the main component of baby food. Another function of carbohydrates of this type is structural, since they are part of the cellulose, which is needed for the formation of plant cells.
Characteristics and features of polysaccharides
Another type of carbohydrates are polysaccharides. This is the most complex type of connections. They consist of a large number of monosaccharides (their main component is glucose). In the gastrointestinal tract, polysaccharides are not absorbed - they are first split.
The features of these substances are:
- insolubility (or weak solubility) in water;
- yellowish color (or no color);
- they have no smell;
- almost all of them are tasteless (some have a sweetish taste).
The chemical properties of these substances include hydrolysis, which is carried out under the influence of catalysts. The result of the reaction is the breakdown of the compound into structural elements - monosaccharides.
Another property is the formation of derivatives. Polysaccharides can react with acids.
The products formed during these processes are very diverse. These are acetates, sulfates, esters, phosphates, etc.
Examples of polysaccharides:
- starch;
- cellulose;
- glycogen;
- chitin.
Educational video material about the functions and classification of carbohydrates:
These substances are important for the full functioning of the body as a whole and cells individually. They supply the body with energy, participate in the formation of cells, protect internal organs from damage and adverse effects. They also play the role of reserve substances that animals and plants need in case of a difficult period.
Disaccharides enter into most of the reactions characteristic of monosaccharides: they form ethers and esters, glycosides, derivatives of the carbonyl group. Reducing disaccharides are oxidized to glycobionic acids. The glycosidic bond in disaccharides is cleaved under the action of aqueous solutions of acids and enzymes. In dilute alkali solutions, disaccharides are stable. Enzymes act selectively, cleaving only ?- or only ?-glycosidic bond /6/.
The sequence of reactions - oxidation, methylation, hydrolysis, allows you to establish the structure of the disaccharide (Fig. 7).
Rice. 7
Oxidation makes it possible to determine which monosaccharide residue is at the reducing end. Methylation and hydrolysis provide information on the position of the glycosidic bond and the size of the cycle of monosaccharide units. The configuration of the glycosidic bond (?? or?? can be determined using enzymatic hydrolysis /1/.
The biological role of disaccharides
Sucrose is broken down in the gastrointestinal tract into glucose and fructose. Sucrose is the most common sugar. Sources of sucrose: sugar beet (14-18%) and sugar cane (10-15%). The content of sucrose: in granulated sugar - 99.75%, in refined sugar - 99.9%.
Sucrose has the ability to turn into fat. Excessive intake of this carbohydrate in the diet causes a violation of fat and cholesterol metabolism in the human body, has a negative effect on the state and function of the intestinal microflora, increasing the proportion of putrefactive microflora, increasing the intensity of putrefactive processes in the intestine, leads to the development of intestinal flatulence. An excess of sucrose in the diet of children leads to the development of dental caries.
Lactose is a carbohydrate of animal origin. During hydrolysis, it breaks down into glucose and galactose. Hydrolysis proceeds slowly, limiting the fermentation process, which is of great importance in the nutrition of infants. The intake of lactose in the body contributes to the development of lactic acid bacteria that suppress the development of putrefactive microorganisms. Lactose is used to the least extent for fat formation and, in excess, does not increase the content of cholesterol in the blood. Source of lactose: milk and dairy products, in which the content of this disaccharide can reach 4-6%.
Sucrose, lactose and maltose are valuable food and taste substances. The sugar industry is engaged in the production of sucrose.
The disaccharide of cellobiose is essential for plant life, as it is a constituent of cellulose /4/.
sucrose glycosidic chemical disaccharide
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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Depending on the number of monosaccharide molecules formed during the hydrolysis of polysaccharides, the latter are divided into oligosaccharides (disaccharides, trisaccharides) and polysaccharides.
Disaccharides are of the greatest practical importance. Disaccharides (bioses) upon hydrolysis form two identical or different monosaccharides. Disaccharides are divided into two groups: reducing and non-reducing.
The connection between two monosaccharide molecules is established using two hydroxyl groups - one from each monose molecule. However, the nature of this relationship may be different. If one of the monosaccharide molecules always provides its hemiacetal (glycosidic) hydroxyl, then the second molecule participates in this either with a hemiacetal hydroxyl (a glycoside is formed - a glycosidic bond) or an alcohol hydroxyl (a glycoside is formed - a glycose bond).
The absence or presence of hemiacetal hydroxyl in a disaccharide molecule affects the properties of disaccharides. If both molecules participated in the formation of a disaccharide with their hemiacetal hydroxyls (glycoside - glycosidic bond), then both monose residues have fixed cyclic forms, and the aldehyde group of such a disaccharide cannot be formed. Such a disaccharide has no reducing properties and is called a non-reducing disaccharide.
In the case of a glycoside-glycose bond, the cyclic form of one monosaccharide residue is not fixed, it can turn into an aldehyde form, and then the disaccharide will have reducing properties. Such a disaccharide is called reducing. Reducing disaccharides exhibit reactions characteristic of the corresponding monosaccharides.
Reducing disaccharides include, in particular, maltose (malt sugar) contained in malt, i. sprouted, and then dried and crushed grains of cereals.
(maltose)
Maltose is composed of two D-glucopyranose residues linked by a (1–4)-glycosidic bond, i.e. the glycosidic hydroxyl of one molecule and the alcohol hydroxyl at the fourth carbon atom of another monosaccharide molecule participate in the formation of an ether bond. The anomeric carbon atom (С 1) involved in the formation of this bond has an α-configuration, and an anomeric atom with a free glycosidic hydroxyl (indicated in red) can have both α - (α - maltose) and β-configuration (β- maltose).
Maltose is a white crystal, highly soluble in water, sweet in taste, but much less than that of sugar (sucrose).
As can be seen, maltose contains a free glycosidic hydroxyl, as a result of which the ability to open the ring and transfer to the aldehyde form is retained. In this regard, maltose is able to enter into reactions characteristic of aldehydes, and, in particular, to give the "silver mirror" reaction, therefore it is called a reducing disaccharide. In addition, maltose enters into many reactions characteristic of monosaccharides, for example, it forms ethers and esters (see chemical properties of monosaccharides).
Sucrose (beet or cane sugar) is a non-reducing disaccharide. It is found in sugar cane, sugar beets (up to 28% of dry matter), plant juices and fruits. The sucrose molecule is built from α,D-glucopyranose and β,D-fructofuranose.
(sucrose)
In contrast to maltose, the glycosidic bond (1–2) between monosaccharides is formed at the expense of the glycosidic hydroxyls of both molecules, that is, there is no free glycosidic hydroxyl. As a result, there is no reducing ability of sucrose, it does not give the "silver mirror" reaction, therefore it is referred to as non-reducing disaccharides.
Sucrose is a white crystalline substance, sweet in taste, highly soluble in water.
Sucrose is characterized by reactions on hydroxyl groups. Like all disaccharides, sucrose is converted by acidic or enzymatic hydrolysis into the monosaccharides of which it is composed.
Polysaccharides are high molecular weight substances. In polysaccharides, monosaccharide residues are linked by glycoside - glycose bonds. Therefore, they can be considered as polyglycosides. The monosaccharide residues that make up the polysaccharide molecule may be the same, but may differ; in the first case, these are homopolysaccharides, in the second, heteropolysaccharides.
The most important polysaccharides are starch and cellulose (fiber). They are built from glucose residues. The general formula of these polysaccharides is (C 6 H 10 O 5) n. Glycosidic (at C 1 -atom) and alcohol (at C 4 -atom) hydroxyls usually take part in the formation of polysaccharide molecules, i.e. (1-4)-glycosidic is formed.
Starch is a mixture of two polysaccharides built from α, D-glucopyranose units: amylose (10-20%) and amylopectin (80-90%). Starch is formed in plants during photosynthesis and is deposited as a "reserve" carbohydrate in roots, tubers and seeds. For example, grains of rice, wheat, rye and other cereals contain 60-80% starch, potato tubers - 15-20%. A related role in the animal world is played by the polysaccharide glycogen, which is "stored" mainly in the liver.
Starch is a white powder consisting of small grains, insoluble in cold water. When starch is treated with warm water, it is possible to isolate two fractions: a fraction that is soluble in warm water and consists of amylose polysaccharide, and a fraction that only swells in warm water with the formation of a paste and consists of amylopectin polysaccharide.
Amylose has a linear structure, α, D-glucopyranose residues are linked by (1–4)-glycosidic bonds. The elemental cell of amylose (and starch in general) is represented as follows:
The amylopectin molecule is built in a similar way, but has branches in the chain, which creates a spatial structure. At branch points, monosaccharide residues are linked by (1–6)-glycosidic bonds. Between the branch points are usually 20-25 glucose residues:
(amylopectin)
Starch is easily hydrolyzed: when heated in the presence of sulfuric acid, glucose is formed:
(C 6 H 10 O 5) n + nH 2 O –– H2SO4,t ° ® nC 6 H 12 O 6
glucose starch
Depending on the reaction conditions, hydrolysis can be carried out stepwise with the formation of intermediate products:
(C 6 H 10 O 5) n ® (C 6 H 10 O 5) m ® xC 12 H 22 O 11 ® nC 6 H 12 O 6
dextrin starch (m A qualitative reaction to starch is its interaction with iodine - an intense blue color is observed. Such staining appears if a drop of iodine solution is placed on a slice of potato or a slice of white bread. Starch does not enter into the "silver mirror" reaction. Starch is a valuable food product. To facilitate its absorption, products containing starch are subjected to heat treatment, i.e. potatoes and cereals are boiled, bread is baked. The processes of dextrinization (the formation of dextrins) carried out in this case contribute to better absorption of starch by the body and subsequent hydrolysis to glucose. In the food industry, starch is used in the production of sausages, confectionery and culinary products. It is also used to obtain glucose, in the manufacture of paper, textiles, adhesives, medicines, etc. Cellulose is the most common plant polysaccharide. It has great mechanical strength and acts as a supporting material for plants. Wood contains 50-70% cellulose, cotton is almost pure cellulose. Like starch, the structural unit of cellulose is D-glucopyranose, the units of which are linked by (1-4)-glycosidic bonds. However, cellulose differs from starch in the β-configuration of glycosidic bonds between cycles and in a strictly linear structure: Cellulose consists of filamentous molecules, which are assembled into bundles by hydrogen bonds of hydroxyl groups within the chain, as well as between adjacent chains. It is this chain packing that provides high mechanical strength, fiber content, water insolubility, and chemical inertness, which makes cellulose an ideal material for building cell walls. The β-glycosidic bond is not destroyed by human digestive enzymes, therefore cellulose cannot serve as food for him, although in a certain amount it is a ballast substance necessary for normal nutrition. Ruminant animals have cellulose-digesting enzymes in their stomachs, so ruminant animals use fiber as a food component. Despite the insolubility of cellulose in water and common organic solvents, it is soluble in Schweitzer's reagent (a solution of copper hydroxide in ammonia), as well as in a concentrated solution of zinc chloride and in concentrated sulfuric acid. Like starch, cellulose undergoes acid hydrolysis to form glucose. Cellulose is a polyhydric alcohol; there are three hydroxyl groups per unit cell of the polymer. In this regard, cellulose is characterized by esterification reactions (the formation of esters). Of greatest practical importance are reactions with nitric acid and acetic anhydride. Fully esterified fiber is known as pyroxylin, which, after appropriate processing, turns into smokeless powder. Depending on the nitration conditions, cellulose dinitrate can be obtained, which is called colloxylin in the technique. It is also used in the manufacture of gunpowder and solid propellants. In addition, celluloid is made on the basis of colloxylin. When cellulose reacts with acetic anhydride in the presence of acetic and sulfuric acids, triacetylcellulose is formed. Triacetylcellulose (or cellulose acetate) is a valuable product for the manufacture of non-combustible film and acetate silk. To do this, cellulose acetate is dissolved in a mixture of dichloromethane and ethanol, and this solution is forced through spinnerets into a stream of warm air. The solvent evaporates and the streams of the solution turn into the thinnest threads of acetate silk. Cellulose does not give a "silver mirror" reaction. Speaking about the use of cellulose, one cannot but say that a large amount of cellulose is consumed for the manufacture of various papers. Paper is a thin layer of fiber fibers, glued and pressed on a special paper machine. From the above, it is already clear that the use of cellulose by humans is so wide and varied that an independent section can be devoted to the use of products of chemical processing of cellulose. Questions for self-control 1. Write the aldehyde formulas of D-glucose, D-fructose. 2. What are the L- and D-, α- and β-forms of sugar? 3. Write the possible cyclic forms of glucose. 4. What is hemiacetal hydroxyl? What are the chemical properties of sugars? 5. Write the reaction equations for the formation of maltose and cellobiose. What is the difference between the formulas of these disaccharides? 6. Give examples of reducing and non-reducing disaccharides. 7. Hydrolysis of starch and fiber. What are the intermediate and final products formed?