The usual sweet sugar used in everyday life is called sucrose. It is an oligosaccharide belonging to the group of disaccharides. The formula for sucrose is C 12 H 22 O 11.

Structure

The molecule contains residues of two cyclic monosaccharides - α-glucose and β-fructose. The structural formula of a substance consists of the cyclic formulas of fructose and glucose connected by an oxygen atom. The structural units are linked together by a glycosidic bond formed between two hydroxyls.

Rice. 1. Structural formula.

Sucrose molecules form a molecular crystal lattice.

Receipt

Sucrose is the most common carbohydrate in nature. The compound is found in fruits, berries, plant leaves. A large number of the finished substance is found in beets and sugar cane. Therefore, sucrose is not synthesized, but isolated using physical impact, digestion and cleansing.

Rice. 2. Sugarcane.

Beets or sugarcane are finely grated and placed in large cauldrons with hot water. The sucrose is washed out, forming a sugar solution. It contains various impurities - coloring pigments, proteins, acids. To separate sucrose, calcium hydroxide Ca(OH) 2 is added to the solution. As a result, a precipitate and calcium saccharate C 12 H 22 O 11 · CaO · 2H 2 O are formed, through which carbon dioxide (carbon dioxide) is passed. Calcium carbonate precipitates, and the remaining solution is evaporated until sugar crystals form.

Physical properties

Main physical characteristics substances:

• molecular weight - 342 g/mol;
• density - 1.6 g / cm 3;
• melting point - 186°C.

Rice. 3. Sugar crystals.

If the molten substance continues to be heated, sucrose will begin to decompose with a color change. When molten sucrose solidifies, caramel is formed - an amorphous transparent substance. In 100 ml of water at normal conditions 211.5 g of sugar can be dissolved, at 0 ° C - 176 g, at 100 ° C - 487 g. In 100 ml of ethanol, under normal conditions, only 0.9 g of sugar can be dissolved.

Getting into the intestines of animals and humans, sucrose under the action of enzymes quickly breaks down into monosaccharides.

Chemical properties

Unlike glucose, sucrose does not exhibit the properties of an aldehyde due to the absence of an aldehyde group -CHO. So qualitative reaction There is no "silver mirror" (interaction with an ammonia solution of Ag 2 O). When oxidized with copper (II) hydroxide, not red copper (I) oxide is formed, but a bright blue solution.

The main chemical properties are described in the table.

Sucrose is not able to oxidize (it is not a reducing agent in reactions) and is called non-reducing sugar.

Application

Pure sugar is used in the food industry for the manufacture of artificial honey, sweets, confectionery, and alcohol. Sucrose is used to obtain various substances: citric acid, glycerin, butanol.

In medicine, sucrose is used to make potions and powders to hide unpleasant tastes.

What have we learned?

Sucrose or sugar is a disaccharide consisting of glucose and fructose residues. It has a sweet taste and dissolves easily in water. The substance is isolated from beets and sugar cane. Sucrose is less active than glucose. It undergoes hydrolysis, reacts with copper (II) hydroxide, forming copper saccharate, does not oxidize. Sugar is used in food, chemical industry, medicine.

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sucrose C 12 H 22 O 11, or beet sugar, cane sugar, in everyday life just sugar - a disaccharide from the group of oligosaccharides, consisting of two monosaccharides - α-glucose and β-fructose.

Chemical properties sucrose

An important chemical property of sucrose is the ability to undergo hydrolysis (when heated in the presence of hydrogen ions).

Since the bond between monosaccharide residues in sucrose is formed by both glycosidic hydroxyls, it does not have restorative properties and does not give a "silver mirror" reaction. Sucrose retains the properties of polyhydric alcohols: it forms water-soluble sugars with metal hydroxides, in particular, with calcium hydroxide. This reaction is used to isolate and purify sucrose in sugar refineries, which we will talk about a little later.

When heated aqueous solution sucrose in the presence of strong acids or under the action of an enzyme invertases going on hydrolysis of this disaccharide to form a mixture of equal amounts of glucose and fructose. This reaction is the reverse of the process of formation of sucrose from monosaccharides:

The resulting mixture is called invert sugar and is used for the production of caramel, sweetening food products, to prevent the crystallization of sucrose, obtaining artificial honey, and the production of polyhydric alcohols.

Relation to hydrolysis

The hydrolysis of sucrose is easy to follow with a polarimeter, since the sucrose solution has right-hand rotation, and the resulting mixture D- glucose and D- fructose has a left rotation, due to the prevailing value of the left rotation of D-fructose. Consequently, as sucrose is hydrolyzed, the angle of right rotation gradually decreases, passes through zero, and at the end of hydrolysis, a solution containing equal amounts of glucose and fructose acquires a stable left rotation. In this regard, hydrolyzed sucrose (a mixture of glucose and fructose) is called invert sugar, and the hydrolysis process itself is called inversion (from Latin inversia - turning, rearranging).

The structure of maltose and celobiose. Relation to hydrolysis

Maltose and starch. Composition, structure and properties. Relation to hydrolysis

Physical properties

Maltose is readily soluble in water sweet taste. Molecular mass maltose - 342.32. The melting point of maltose is 108 (anhydrous).

Chemical properties

Maltose is a reducing sugar because it has an unsubstituted hemiacetal hydroxyl group.

By boiling maltose with dilute acid and by the action of an enzyme maltose hydrolyzes (two molecules of glucose C 6 H 12 O 6 are formed).

Starch (C 6 H 10 O 5) n polysaccharides of amylose and amylopectin, the monomer of which is alpha-glucose. Starch, synthesized different plants in chloroplasts, under the influence of light during photosynthesis, it differs somewhat in the structure of grains, the degree of polymerization of molecules, the structure of polymer chains, and physicochemical properties.

Physical properties

Pure sucrose is a colorless crystalline substance with a sweet taste, highly soluble in water.

Chemical properties

The main property of disaccharides, which distinguishes them from monosaccharides, is the ability to hydrolyze into acidic environment(or by the action of enzymes in the body):

C 12 H 22 O 11 + H2O> C 6 H 12 O 6 + C 6 H 12 O 6

Sucrose glucose fructose

Glucose formed during hydrolysis can be detected by the "silver mirror" reaction or by its interaction with copper (II) hydroxide.

Obtaining sucrose

Sucrose C 12 H 22 O 11 (sugar) is obtained mainly from sugar beet and sugar cane. In the production of sucrose, chemical transformations do not occur, because it is already present in natural products. It is only isolated from these products as pure as possible.

The process of isolating sucrose from sugar beets:

Peeled sugar beets in mechanical beet cutters are turned into thin chips and placed in special vessels - diffusers, through which they pass hot water. As a result, almost all sucrose is washed out of the beets, but with it various acids, proteins and coloring substances pass into the solution, which must be separated from sucrose.

The solution formed in the diffusers is treated with milk of lime.

C 12 H 22 O 11 + Ca(OH) 2 > C 12 H 22 O 11 2CaO H 2 O

Calcium hydroxide reacts with the acids contained in the solution. Since the calcium salts of most organic acids are sparingly soluble, they precipitate. Sucrose, on the other hand, with calcium hydroxide forms a soluble sucrose of the alcoholate type - C 12 H 22 O 11 2 CaO H 2 O

3. To decompose the resulting calcium sucrose and neutralize the excess of calcium hydroxide, carbon monoxide (IV) is passed through their solution. As a result, calcium is precipitated in the form of carbonate:

C 12 H 22 O 11 2CaO H 2 O + 2CO 2 > C 12 H 22 O 11 + 2CaCO 3 v 2H 2 O

4. The solution obtained after precipitation of calcium carbonate is filtered, then evaporated in vacuum apparatus and sugar crystals are separated by centrifugation.

However, it is not possible to isolate all the sugar from the solution. A brown solution (molasses) remains, which contains up to 50% sucrose. Molasses is used to produce citric acid and some other products.

5. Isolated granulated sugar usually has a yellowish color, as it contains coloring matter. To separate them, sucrose is redissolved in water and the resulting solution is passed through Activated carbon. Then the solution is again evaporated and subjected to crystallization. (see annex 2)

Application of sucrose

Sucrose is mainly used as a food product and in the confectionery industry. By hydrolysis, artificial honey is obtained from it.

Being in nature and the human body

Sucrose is a component of sugar beet juice (16-20%) and sugar cane (14-26%). In small quantities, it is found together with glucose in the fruits and leaves of many green plants.

Sugar is the colloquial name for sucrose. The formula looks like this: C12H22O11. Sugar is mainly extracted from cane or beets. It is an essential component of cell nutrition, indispensable for the brain. is the purest carbohydrate that provides physical and mental activity. Unlike starch, which is also a carbohydrate, it is quickly processed and absorbed by the body. The digestive tract breaks down sucrose into the simple sugars glucose and fructose. Glucose provides more than half of the body's energy costs.

Physical and chemical properties of sugar

Sucrose is a colorless crystal, easily soluble in water. The whiteness is explained by the fine fraction and the refraction of light by the edges. At a temperature of 160 ° C, melting occurs, with solidification a viscous translucent mass is formed called caramel.
Sucrose has a complex molecular structure compared to glucose. Contains a hydroxyl group (OH), as evidenced by the tolerance of sugars to metal oxidation. Aldehydes (alcohol devoid of hydrogen) are found in all classes of carbohydrates except sucrose. However, it manifests itself with glucose when the sugar molecules are broken down into digestive system organism.
Sucrose is the most important element among disaccharides, the molecules of which consist of two atoms. In this case, from glucose and fructose. Unlike the others (lactose, maltose, cellobiose), sucrose is the most carbohydrate sugar.

The molar mass of sucrose is 342 g/mol

Useful properties of sugar

The main consumer of glucose in the human body are brain neurons. Oxygen and sugar are the main nutrients of the central nervous system. Glucose is essential for metabolism. Nourishes the cardiovascular system.
As you know, glucose promotes the release of endorphins (hormones of happiness), which are a natural defense against stress. Sweet tea or chocolate the best helpers in exams or interviews.

Harmful properties of sugar

The harm that sugar causes to the body is difficult to overestimate. An excess of sugar causes irreparable damage to the liver, enveloping it in fatty layers. Similarly, fructose enters the heart, which leads to heart attacks, coronary disease.
Sugar is a nutrient not only for the brain, but also for bacteria. Plaque on teeth or in crevices, hard-to-reach places oral cavity can contain the lion's share of sticky sugar, which is a cozy environment for the reproduction of hundreds of types of pathogenic microflora. With an increase in appetite, oral inhabitants take on tooth enamel and dentin, which leads to caries.
Sugar contains no nutrients other than carbohydrates. It is highly undesirable to use it in its pure form. redundant

Sucrose is found in many varieties of fruits, berries and other plants - sugar beet and sugar cane. The latter are used in industrial processing to obtain sugar, which is consumed by people.

It is characterized a high degree solubility, chemical inertness and non-involvement in metabolism. Hydrolysis (or the breakdown of sucrose into glucose and fructose) in the intestine occurs with the help of alpha-glucosidase, located in the small intestine.

In its pure form, this is a colorless monoclinic crystals. By the way, the well-known caramel is a product obtained by solidifying molten sucrose and further forming an amorphous transparent mass.

Many countries are engaged in the extraction of sucrose. Thus, according to the results of 1990, world sugar production amounted to 110 million tons.

Chemical properties of sucrose

The disaccharide dissolves rapidly in ethanol and less in methanol, and also does not dissolve at all in diethyl ether. The density of sucrose at 15 degrees Celsius is 1.5279 g/cm3.

It is also capable of phosphorescence when cooled by liquid air or actively illuminated by a stream of bright light.

Sucrose does not react with the reagents of Tollens, Fehling and Benedict, does not show the properties of aldehydes and ketones. It was also found that when a solution of sucrose is added to copper hydroxide of the second type, a solution of copper saccharate is formed, which has a bright blue light. The disaccharide lacks an aldehyde group; the other sucroses are maltose and lactose.

In the case of an experiment to identify the reaction of sucrose with water, the solution with disaccharide is boiled with the addition of a few drops of hydrochloric or sulfuric acid, and then neutralized with alkali. Then the solution is heated again, after which aldehyde molecules appear, which have the ability to reduce copper hydroxide of the second type to the oxide of the same metal, but already of the first type. Thus, the assertion is proved that sucrose, with the participation of the catalytic action of the acid, is capable of undergoing hydrolysis. As a result, glucose and fructose are formed.

There are several hydroxyl groups inside the sucrose molecule, due to which this compound can interact with copper hydroxide of the second type according to the same principle as