& NBSP General and One of the most frequently used to obtain aldehydes reaction is the oxidation of primary alcohols:

& NBSP As an oxidizing agent, chromic acid is usually used in the interaction of two-axis potassium or sodium with sulfuric acid.

& NBSP When producing formaldehyde from methyl alcohol, use as oxidizing air in the presence of a catalyst - metal copper. The effect of copper as a catalyst for the first time I was observed by I. A. Helukov.

& NBSP Aldehydes are also obtained by cleaving hydrogen from primary alcohols when passing their vapors over heating up to 600 ° C brass or zinc chips playing the role of catalyst:

& NBSP Extremely important technical significance for the preparation of aldehydes also has the reaction of M. G. Kucherov - the accession of water to acetylene and its homologues in the presence of mercury salts (playing the role of catalyst):

& NBSP acetic aldehyde, or acetaldehyde, it turns out when the ethyl alcohol is oxidized with a chromium mixture.

& NBSP forming aldehyde is easily oxidized further into acetic acid; Therefore, such conditions should be created for the reaction so that the resulting aldehyde is able to be quickly removed from the reaction mixture. This is reached, firstly, gradually taking the oxidizing agent and, secondly, passing through the reaction mixture of carbon dioxide. The van trapped acetaldehyde is enjoyed by a stream of carbon dioxide along with a certain number of alcohol, water and acetal vapors. Most of these impurities have time to condense in the refrigerator, and the pair of aldehyde passed through the refrigerator is absorbed by the ether cooled with a mixture of ice and salt. Since it is impossible to separate the aldehyde from the solvent distillation, then the aldehyde is translated into well crystallizable aldehydamiak; Clean aldehyde is obtained by decomposing aldehydeamiaics with sulfuric acid.

& nbsp. Reagents:
& NBSP alcohol 95% ........................... 30 ml (about 0.5 praying)
& NBSP Double Sodium Sodium (or Potassium) ..... 48 g (0.16 praying)
& nbsp sulfuric acid; ether; carbon dioxide (from the cylinder); Ammonia (from the balloon)

& NBSP The half-liter round bottom flask is closed with a rubber plug with three holes (Fig. 35). In one of these holes, the curved nozzle, connected under reflux, is inserted into the other - the drip funnel and in the third - the tube to transmit carbon dioxide almost to the bottom of the flask. The refrigerator through a small U-shaped tube filled with the calcined calcium chloride is connected to a washing flask containing 100 ml of ether. The flushing flask is cooled to 10-15 ° in a mixture of crowded ice and salt.

& NBSP in the flask pour alcohol and a mixture of 10 ml of concentrated sulfuric acid and 20 ml of water and heated to a boil; Heating the flasks should be conducted on an electric slab with a closed spiral. Then a mixture of 85 ml of water and 25 ml of concentrated sulfuric acid is prepared, dissolved in this mixture a two-axis sodium and a warm solution is poured into a drip funnel, following the funnel tube to be filled with liquid. Gradually adhere to a chromium mixture to a boiling alcohol, at the same time passing through the liquid a jet of carbon dioxide (at such a speed so that undergoing gas bubbles can be considered).

& NBSP Since the reaction comes with heat release, the mixture continues to boil without heating from the outside. After about 20 minutes. The adhesiveness of the chromium mixture finish. After that, supporting the weak boil of the reaction mixture, continue to pass carbon dioxide for about 10 minutes to completely remove the aldehyde from the flask.

& NBSP To highlight the resulting aldehyde from the solution on the air (located in the washing flaw), it is translated into aldehydeamiak. To this end, the auxiliary solution of aldehyde, cooled by a mixture of ice and salt, through a wide tube (a narrow tube is quickly clogged with crystals) are passed by dry ammonia until the solution becomes strongly smelling. During the transmission of ammonia, part of the ether evaporates, so the work should be made away from the burning burners.

& nbsp an aldehyde ether solution saturated with ammonia leaves to stand in the cooling mixture for 1 hour; The aldehydamiak crystals that excreted during this time are scraped from the vessel walls, suck on the bureau funnel and washed with a small amount of ether. They are dried first on the filter paper in the air, and then in the desiccator over sulfuric acid without a vacuum.

& NBSP Output 10-12

& NBSP The resulting preparation can be stored in a well-clogged flask for several days.

& NBSP The output can be increased to 15-17 g if when receiving aldehyde to skip a stronger jet of carbon dioxide, pass through the refrigerator water with a temperature not higher than 10 ° and apply two flushes with ether cooled to -15 & deg to absorb the aldehyde vapor.

& NBSP for decomposition of aldehydamiak 10 g is dissolved in 10 ml of water and add a well-cooled mixture of 7 ml of concentrated sulfuric acid and 20 ml of water. From the solution aldehyde is distilled off in a water bath. As a receiver take a small distillation flask; It is attached to the refrigerator with the help of rubber plugs and curved nozzle so that the end of the nozzle entered the balloon of the flask. The receiver is cooled by a mixture of ice and salt.

& NBSP tempo. kip. aldehyde 21 °; UD. Weight 0,7876.

& nbsp. Obtaining gaseous ammonia. If there is no balloon with ammonia in the laboratory, then dry ammonia is obtained by boiling a concentrated ammonia solution in a round-bottom reflux flask. The released ammonia for drying is passed through a column filled with solid caviar pots and natron lime (Fig. 36).

& NBSP aldehydes are easily oxidized and therefore are good solvents. This property can be used to restore silver salts to metal; Under certain conditions, silver can stand out on the walls of the test tube, forming a mirror. This reaction is one of the characteristic for aldehydes.

& NBSP In a thoroughly washed alkali solution, a 3 ml of a 5% solution of nitrogen silver is taken to distilled with distilled water and add a diluted ammonia solution (1 ml of a concentrated ammonia solution is diluted with 10 ml of water) to dissolve the sediment initially appeared. A single drop of aldehyde (or a few drops of aldehydeamiak aldehydeamiaka) is added to the resulting ammonium solution of silver (or several drops of aqueous solution of aldehydamiak). If the selection of silver is too slow, the test tube is carefully heated in a glass with water.

& NBSP Aldehyde oxidation with ammonia solution of silver oxide is significantly accelerated in the presence of alkali. For the preparation of a quick-acting reagent to the ammonium silver oxide solution obtained above, 1 drop is added 1 drop of a 10% solution of caustic soda and, in the case of falling out, the precipitate is dissolved by adding ammonia. This reagent formaldehyde and acetaldehyde is quickly oxidized at room temperature.

& NBSP A characteristic qualitative reaction to aldehydes is the interaction with fuchsine acid (fuchsin, discolored with sulfuric acid). Fuchene with sulfuric acid gives colorless connections. The latter at the addition of aldehyde are partially moving to the quinoid dye (painted in red).

& NBSP A small amount of fuchsine is dissolved in such a number of hot water so that approximately 0.2% solution turned out. A saturated aqueous solution of sulfuric acid is added to the cooled solution to complete discoloration. Several milliliters of the obtained reagent are poured into the tube and add a few drops of aldehyde aqueous solution. It turns out red staining.

& NBSP If the aldehyde is difficult to soluble in water, such as benzoic aldehyde, then a little algel alcohide is added to the reagent.

& NBSP for acetic aldehyde is also very characteristic of the condensation in Aldol, open by A. P. Borodin.

& NBSP The development of our knowledge about the nature of aldehydes contributed a lot to the work of A. M. Butlerova. In 1859, the polymerization of formaldehyde was first obtained trioximetylene, which is a crystalline substance distinguishing without decomposition and not possessing reducing properties; The molecular weight of trioximetylene corresponds to the formula (CH 2 O) 3. In accordance with this, he is attributed to the cyclic structure:

& NBSP A. M. Butlers in 1861, exploring the condensation reaction of formaldehyde in the presence of limestone or barite water, first received a substance called by the methylhenitan relating to the class of carbohydrates (sugars).

& NBSP Later E. Fisher from this product allocated hexose, called across them. Acrosis is a racemic mixture d.- I. l.-Fructose.

& NBSP Isovalerician aldehyde is obtained similar to the acetic aldehyde by oxidation of isoamyl alcohol with a chromium mixture:

& NBSP The smaller solubility of isovalarian aldehyde in water slightly reduces the rate of its further oxidation into isovalaric acid, but a higher boiling point of aldehyde (92 ° C) makes it difficult enough to remove it from the reaction mixture. Therefore, in the reaction products, along with aldehyde and a certain number of unreacted alcohol, an isovalarianic acid and its ester with isoamyl alcohol are also present. To remove acid, the reaction product is treated with soda, and for the separation of aldehyde from other impurities it is transferred to the crystalline bisulfite derivative:

& NBSP Currently, the bisulfite compounds of the aldehydes are considered as salts of a-oxysulfonic acids, in which the sulfogroup is influenced by the adjacent hydroxyl.

& NBSP decomposing the bisulfite derivative solution of soda, a clean aldehyde is obtained.

& nbsp. Reagents:
& NBSP isoamyl alcohol .......... 13.2 g (0.15 praying)
& NBSP Two-oxidine Potassium ..... 16.5 g (about 0.06 praying)
& nbsp sulfuric acid; Sodium carbon dioxide; sodium bisulfite; ether; calcium chloride

& NBSP into a semi-linette distillation flask, connected to a downward refrigerator, placed a mixture of 16.5 g of two-axis potassium, 160 ml of water and 16 ml of concentrated sulfuric acid. The mixture is heated to 90 ° and drops from a drip funnel with an isoamyl alcohol, all the time mixing the contents of the flask all the time. Since the oxidation of alcohol is accompanied by a large heat release, the reaction should be kept slowly, with caution, to avoid rapid boiling and throwing the contents of the flask. After all the alcohol fit, the flask is heated for another 15-20 minutes on a boiling water bath; At the same time, the aldehyde is partially distilled off. Then remove the bath, wipe the flask outside, substitute the asbestos mesh and, heating the mixture on the burner to a boil, the aldehyde is distilled off.

& nbsp distillate separated by two layers is treated with a solution of sodium acetic acid to the appearance of an alkaline reaction (via Lacmus); The upper layer consisting of aldehyde and unreacted alcohol is separated using a dividing funnel and shacks with an equal size of a saturated sodium bisulfite solution. The supposed crystals of the bisulfite derivative suck on the bureau funnel, washed with ether, pressed between the leaves of the filter paper and dried in the desiccator over calcium chloride.

& nbsp exit about 15 g

& NBSP To isolate aldehyde in a free state, the bisulfite derivative is decomposed with a solution of sodium carbon dioxide, aldehyde is separated using a dividing funnel, dried with a small amount of calcium chloride and distilled.

& NBSP tempo. kip. 92 °; UD. Weight 0.803.

& nbsp isovalaria aldehyde can be characterized by translating it into p-Nitrophenylhydron, melting at 109 ° C. Obtaining p-Niatrophenylhydrasons are described below.

& NBSP Isovalerician Aldehyde gives the same reaction as acetic aldehyde.

& NBSP When oxidizing primary alcohol (or aldehyde), carboxylic acid is obtained with the same number of carbon atoms. During the oxidation of the ketone (or secondary alcohol), it cannot be obtained with an acid with the same number of carbon atoms: the connection between the carbonyl group and one of the alkyl residues is broken and the acid containing a smaller number of carbon atoms is formed than the oxidation of ketone (ketone oxidation rule A. N. Popova).

& NBSP When producing acids by oxidation compounds containing a primary alcoholic, aldehyde or methyl group, a manganese-oxidant potassium in an alkaline medium, a chromium mixture or nitric acid is used as oxidizing agents. Usually the most smooth formation of appropriate acids is the oxidation of manganese-oxidal potassium. The disadvantages of this method include high consumption of comparatively expensive manganese powder potassium and in some cases too energetic effect of this oxidant, as a result of which the main product of the reaction is subjected to further oxidation.

& NBSP When oxidizing primary alcohols, a mixture of chromium and sulfuric acids, the formation of a significant number of by-products - aldehydes, esters, acetals is observed. Under more stringent oxidation conditions, the listed by-products are obtained in smaller quantities, but the acidic acid is partially subjected to deeper oxidation. In some cases, good results are obtained by applying nitric acid.

& NBSP Isobutyl alcohol oxidation in isomaslane acid can be carried out as a treatment with an alkaline solution of manganese-oxid potassium on cold:

so and by heating with a chromium mixture. The first method gives a significantly better acid yield.

& nbsp. Reagents:
& NBSP isobutyl alcohol ........... 14.8 g (0.2 praying)

& nbsp carbon dioxide sodium; sulfuric acid; ether; sodium sulphate

& NBSP in a liter flask mix isobutyl alcohol with 45 ml of water and add 12 g of crystalline sodium carbon dioxide. The mixture is cooled in ice water and with continuous stirring and cooling with water, a cooled solution of manganese-solid potassium in 800 ml of water is gradually adhered; The temperature should not rise above 5 °.

& NBSP The reaction mixture is left to stand for 12 hours. At room temperature, after which the resulting dioxide of manganese was filtered off, washed with water (connecting the washing water to the filtrate) and the filtrate was evaporated on a water bath to a volume of 40-50 ml.

& NBSP in cooling The solution is transfused into a separatory funnel, add 10% sulfuric acid to an acidic reaction (Congo Red), an even small excess of its excess is introduced and then 20 ml of ether is added. The mixture shakes, divert the aqueous layer and treated it two more times (10 ml). The connected essential extracts are dried with anhydrous sodium sulfate.

& NBSP After sufficient standing over sulfate sodium, the ethereal solution is filtered off, washing the precipitate with a small amount of dry ether and overflow the solution into the distillation flask. The ether is distilled off in a water bath, then replace the water refrigerator with air and, heating the flask with a small flame of the burner, is distilled with isomaslane acid.

& NBSP output about 14

& NBSP tempo. kip. 154.4 & DEG.

& NBSP isoamyl alcohol oxidation reaction, leading to the formation of isovalaric acid, flows according to the equation:

& nbsp. Reagents:
& NBSP isoamyl alcohol ............ 22 ml or 17.6 g (0.2 pray)
& NBSP manganese-oxid potassium ....... 42 g (0.27 pray)
& nbsp acetate sodium; sulfuric acid; ether; sodium sulphate

& NBSP Work is performed similar to the preparation of isomaslane acid.

& NBSP output about 16

& NBSP tempo. kip. Isovaleryanic acid 176.7 & deg.

& NBSP When the glucose oxidation of nitric acid oxidation is subjected to aldehyde and primary alcohol groups with the formation of two-born sugar acids:

& NBSP This reaction is often used to detect glucose in sugars extracted from natural products, since none of the monomosis, in addition to glucose, does not give a sugar acid during oxidation. To isolate sugar acid from the reaction mixture, relatively small solubility in its acidic potassium salt is used.

& nbsp. Reagents:
& nbsp glucose .................................... 5.4 g (0.03 praying)
& NBSP nitric acid 25% (UD. Weight 1.15) ..... 32 ml (0.15 praying)
& nbsp Carbon dioxide; acetic acid; Active coal

& NBSP work lead under the craving.

& NBSP In a porcelain cup, glucose with nitric acid is mixed and the solution is heated on a weakly boiling water bath, continuously stirring the liquid with a glass wand. Heating is leading until nitrogen oxides stops, and the liquid, removed to the syrup consistency, will not begin to be painted in yellow.

& NBSP The resulting syrup-shaped mass is dissolved in a small amount of water (6-8 ml) and, heating on a water bath, gradually neutralize (before alkaline reaction in Lacmus) with carbon dioxide powder. Thus, the well-soluble average potassium salt of sugar acid is translated into an acidic salt using acetic acid. To do this, it is added dropwise ice acetic acid to the cooled solution when stirring the glass stick until the solution begins to smell acetic acid.

& NBSP The mixture is left to stand at night, and the next day they filtered on a small bureauxer funnel that dropped crystals of acidic hydraulic salt of sugar acid. The crystals are washed with several drops of icy water and recrystallize them from the possibility of a small amount of hot water, pre-boil the solution with active coal and filtering it on the Buchner funnel. Clean crystals of acidic potassium acid crystals drop out of cooling filtrate. They are sucking and dried between the leaves of the filter paper.

& NBSP output about 2 g

& NBSP For characterization of sugar acid, it is translated into a silver salt and determine the content of silver in the latter. For this, the acidic potassium is dissolved in a small amount of water, neutralized by ammonia, removed excess ammonia with boiling and cooled is precipitated with a solution of nitric acid silver (nitric acid silver are taken in one-hour quantity in relation to the weight of hydrochloric acid potassium salt). The silver salt was sucked off on a small filter, pressed between the leaves of the filter paper and dried in a vacuum-excitator over sulfuric acid in the dark, since the silver salt is gradually decomposed.

& NBSP Side Silver Salt is placed in a crucible and calcined. Silver hydrochloric salt must contain 50.90% silver, which corresponds to the formula AG 2 C 6 H 8 O 8.

& NBSP The benzene core is characterized by great resistance to oxidizing agents; Therefore, for example, under the action of chromic acid oxidation, side chains are subjected to the formation of carboxyl derivatives of benzene. So, benzoic acid is progressing from toluene:

& NBSP As an example of the oxidation of the side chain of the aromatic compound into the carboxyl group below is a description of obtaining p-Nitrobenzoic acid p-Trotololoola, oxidizing easier than toluene:

& nbsp. Reagents:
& nbsp. p-Nithrololoole ........................... 13.7 g (0.1 praying)
& nbsp two-sized sodium (or potassium) ..... 42 g (about 0.14 praying)
& nbsp sulfuric acid; sodium hydroxide; benzene

& NBSP In a round bottom flask with a capacity of 250-300 ml, equipped with a mechanical stirrer, poured 90 ml of water and add a two-axis sodium and nitrotoluole. Stripping stirrer and continued 15-20 minutes. 55 ml of concentrated sulfuric acid are adhered. Due to the interaction of sulfuric acid with water, the temperature of the mixture rises, the nitrotrolol is melted and the energetic oxidation reaction begins. After adding a half-number of acidic acid, the remaining acid should be added at such a speed to avoid too rapid reaction flow. Since this is a small amount of nitroleoloola, it should be done in the exhaust cabinet.

& NBSP After all sulfuric acid and self-heating of the reaction mixture will be added, the flask is closed with a plug into which a wide glass tube (playing the role of the reverse refrigerator) is inserted, the mixture is heated on the grid to weak boiling and boil for even half an hour.

& NBSP in cooling in the reaction mixture is poured 120 ml of water and cooled again; The highlighted nitrobenzoic acid is filtered off, sucking through paper or, better, linen filter, and washed 60 ml of water. In order to fully remove chromium salts, raw nitrobenzoic acid is heated on a water bath with 60 ml of 5% sulfuric acid, a well-haired mixture. The crystals are suused, dissolved in a 5% solution of caustic soda, filtered from impurities (chromium oxide hydrate, unreacted nitrotoluolet) and the filtrate with stirring is poured with a thin jet into a 5% solution of sulfuric acid; The latter is taken in some excess to the amount necessary to neutralize the entire caustic NATR. The precipitated precipitate is sucking, flushing first with a small amount of diluted sulfuric acid, then clean water and dried.

& NBSP exit about 10 g

& NBSP tempo. pl. Pure product 240 & deg.

& NBSP If the preparation obtained is not clean and not melted with proper temperature, it should be recrystallized from benzene.

& NBSP received p-Nitrobenzoic acid can be used to obtain a chloride p-Nitrobenzoye.

& NBSP In the absence of a mechanical stirrer can be limited to energetic stirring of the reaction mixture from hand. When working with large quantities, it is necessary to use a stirrer, connecting the flask under reflux and skipping the axle of the agitator through the refrigerator. Sulfuric acid across the drip funnel. The yield of the product is equal to the weight of the nitroleol taken.

Sleeping and sugarcic acids

C 6 H 10 O 8. - these are an important class of compounds for sugar substances, in particular for hexosis and their derivatives, being relatively persistent products of their oxidation; With the help of these acids, it is possible to often determine the nature of hexose or its derivative, exposing them to oxidation (see the plant and gum mucus). All these acids are derivatives of two-headed adipic acid coton-CH 2 -CH 2 -CH 2 -CH 2 -COs, formed by substitution in each group of CH 2 of one hydrogen atom with aqueous residue (tetraxiadipic acids). Thus, for all acids of this series, the general structural formula is:

Acid acids of such a structural formula, however, a lot from each other is known, and this phenomenon finds itself an explanation in the stereochemical construction of their particles. As can be seen from the reduced formula of the acid, there are four asymmetric (see stereochemistry) of the carbon atom (marked with circles and cross), and two of them (for example, marked with cross) are quite different - identical and different from other two (designated circles ), which in turn is equal to each other. The presence of four such carbon atoms is due to the possibility of existence of 14 stereochemical isomers, from among which 8 should be optically active, 4 - notable, but representing equivalent to the number of particles a mixture of mutually neutralizing right and left isomers and, trace. Mighting to be decomposed on optical components, and, finally, 2 - negative, which decomposition on optical components should not be bred, as not formed from optical antipodes - neraceemic mixtures; Isomers these are not relevant due to the mutual neutralization of equivalent asymmetric carbon atoms in the same particle (like meson acid). All 14 isomers are known, although not everyone has been studied with the same completeness; They are obtained by the oxidation of hexosis and their derivatives or corresponding to hexosis of six-coat alcohols (hexides), with which the acids have a great similarity in the identity of the extreme groups of the carbon chain of each particle; Similarities are, as well as the main phases of transitions, are easily understandable by formulas:

CH 2 ON- (CH-ON) 4 -CH 2 it is hexith

SNO- (CH-ON) 4 -CH 2 hexose

Soam- (CH-OH) 4 -Сh 2N - Hexson Acid

Soam- (CH-OH) 4 -Conoons - tetraxiadipic acid.

The stereochemical difference of C. and sugar acids consists in different spatial arrangements of the aqueous residues and hydrogen atoms associated with an asymmetric carbon atom. To get acquainted with the image of the image of their structure, we will analyze the formula, for example, ordinary S. acid and then we turn to the image of the rest of the isomers. For C. Acid, which is just one of those two, which are optically notionless and decomposition into active ingredients, this formula is derived:

Or schematic:

It is formed when the galactose oxidation is formed, and it is indifferent whether the right or left galactose is oxidized, it turns out the same negative necrotized S. Acid:

The complete identity of both formulas for C. Acid is easy to notice if one of the formulas turn in the paper plane by 180 °. In addition to ordinary S. acid, there are still non-uracemic aloshlisic acid and d-, l-, I. i- Taloslese; from sugar acids - d-, L-, V-, I- sugar d-, L- and i- Man alcohol I. d-, L- and i- Asharic acids. The structure of them and communication with respective hexoses are visible from the trail. Comparison:

Which, in turn, show a very interesting ability to restore under the influence of sodium amalgam into all the above sequential stages to hexides inclusive; Then, when heated with strong acids C. and sugar acids go to furandiqarboxylic acid:

Called otherwise dehydroslize Acid, which, on its part, with further heating loses the elements of carbon dioxide and goes into furancarboxylic acid, known as pirosalis acid. In addition to the listed reactions and transitions, some less characteristic on which we will not stop are known.

From private properties as the most important can be specified on the following: D- and l-sugar Acids are obtained when oxidizing nitric acid d- and l. -glucosis, gulzo and their derivatives; These acids are not obtained in crystalline; They are easily soluble in water and when the aqueous solution is evaporated, lactone crystals are isolated from 6 H 8 O 7, melting. at 130-132 °; UD. Rotate. Fresh solution of the right isomer [α] D. \u003d +37.9 °. For sugar acids, their acidic potassium salts with 6 H 9 o 3 K, work-soluble in water (1: 6 8) are most characteristic; i. -sharic acid repeats the properties of active acids, the mixture of which it is; d- and L-carnamic acids Formed during the oxidation of the mannose and their derivatives, in the free state of the acid is easily transmitted to dilactons, crystallizing with two particles of water, from 6 H 6 o 6 ∙ 2N 2 o; Water crystals for l. -dilatone melted at 68 °, the anhydrous dilactons, decomposing, melted between 180 ° -190 °; Dilacton soluble in water in quantity of 1: 5-6 hours; UD. Rotate. [α] D. \u003d ± 201 ,80; acidic potash salts of them are easily soluble and are not characteristic, as not characteristic of other salts; i. -Manyahane acid representing a mixture of both isomers, in general repeats their properties, except, of course, optical activity; d- and L-idea-chicken acids obtained in the form of syrups with oxidation of nitrogen acid d- and l. -donic acids - monocarbonyl acids - C 6 H 12 O 7, responding to hexosam - Idozam; i. -dosharic acid represents a mixture d- and l- Isomers; d- and L-Taloslese Acid: d. - Cotton is obtained when oxidation with nitrogen acid d. -Talonic acid corresponding to hexose - d. -thelosis; Crystallizes in the form of plates, melted, decomposing, at 158 \u200b\u200b°, rotates to the right, [α] D. \u003d + 29.4 °; When boiling aqueous solution forms lactone, rotating left; l. - Totalizing acid is obtained when oxidizing β-radiation acid nitrogen

Crystal; Rates left, [α] D. \u003d -33.9; Both isomers when heated in the presence of pyridine (in order to avoid the formation of lactones), it is converted into stereoisomer - S. acid; i. - Silot represents a mixture d- and l. - Shell. Mucium acid, one of two negative neraceremic tetraxiadipic acids; It was discovered yet in the town of Scheel in the oxidation of nitric acid of milk sugar; It is formed during the oxidation of galactose and its derivatives or substances that conclude it, like gum, mucus (hence the origin of the name of acid), etc. It represents a microcrystalline powder dissolving at 14 ° B of 300 hours of water (difference from sugar acid), at 100 ° - at 60 h; melts, decomposing, at 213 °; When the aqueous solution is heated, it turns into a non-micrifelid, easily soluble lactone - C 6 H 8 O 7, previously considered an izomer C. acid and known under the name paraslize acid; Lacton, in contrast to the acid itself, is restored by the amalgam sodium. C. Acid gives some characteristic salts and ethers. When heated in the presence of pyridine, the part turns into his stereoisomer - aloslize acid. Almoslisian Acid It is formed when heated 1 hour. S. acid, 10 hours of water and 2 h. Pyridine or quinoline (for protection from lactone formation) to 140 ° for 3 hours; At the same time, however, only part of S. acid turns into an aloslize, since the latter, in turn, in these conditions is is amazed in S. acid; Movable equilibrium comes. Aloshlic acid is lighter soluble in water (1 hour in 10-12 hours. Boiling water), rather than C. acid than and enjoyed to obtain it in clean water; negative and neracessic; melts, severely decomposing, between 166-171 °; When the aqueous solution is evaporated, it forms lactone; Potash salts, intronic, ammonium and magnesium are lighter than soluble in water, which is the same for C. acid. In addition to the listed two-headed hexiatric acids, another acid is known noriSosharian - C 6 H 10 O 8, which differs from other tetraxiadipic acids with its inability to form lactones; water particle, however, loses it easily and passes into acid isozhar -C 6 H 8 O 7, which is also a two-axis acid, in the formation of which, obviously, the water was separated from two alcohol water residues, without the participation of carboxylov. Both of these acids are formed during the oxidation of nitric acid chitosamine (hexosamine) corresponding to glucose - chitosis, a non-established structure formed during the decomposition of chitin. The structure of the structure leading for isosaharic acid

It should be considered that does not correspond to reality, since then norizosacheric acid would have to be a normal tetraxiadipic acid; Above, however, all possible spatial configurations are listed for tetraxiadipic acids that are all known. Apparently, chitosis, nori-zeroic acid and isosaperic acid do not have a normal carbon skeleton. In conclusion, it remains to mention another acid called Parasharnya acid; It is formed with the decomposition of the sulfuric acid glucoside of the licorice root - glycerizine; Its formula is also with 6 H 10 o 8, it is still not sufficiently studied and, apparently, belongs not to tetraoxychlotes, but to ketoxic acids.

The representative is a D-glucuronic acid formed from glucose.

Glucuronic acid is a structural component of polysaccharides. It is independently involved in the formation of toxic substances, forming water-soluble glucuronides with them, and displays them with urine.

The removal of salicylic acid from the body in the process of exposure to medicinal substances occurs in the form of an o-glucuronide generated by the place of semi-acetate hydroxyl glucuronic acid and phenolic hydroxyl salicylic acid.

Neraminic acid. It turns out as a result of the aldol condensation of PVC and D-aminosamine. (Angle22)

Salicylic acids. They are N-acetyl neuramic acid derivatives. The acylation occurs acetyl or hydroxyacetyl residue. For example, N-acetyl-d-neuraminic acid has the following structure (Angle23)

Neramic and sialic acids are in free state are contained in the spinal fluid. Salahic acid is a component of specific blood substances, is part of the ganglioside of the brain and participates in the conduct of nerve impulses.

FROMfalse carbohydrates

Polysaccharides are high-molecular carbohydrates, in chemical nature related to polyglycosides, i.e. Monosaccharide polycondensation products related to among themselves glycosidic bonds. Polysaccharides have a large molecular weight and are characterized by a high level of the macromolecule structural organization. Polysaccharide skeins can be branched and unwanted, i.e. linear.

According to the composition of polysaccharides divide on:

1. homopolisaccharides - Biopolymers formed from the remains of one polysaccharide

2. heteropolisaccharides - formed from remnants of different monosaccharides.

All of them have a common name - glycans.

G.omopolesaccharides

Biologically important includes starch, glycogen, and fiber, consisting of glucose residues.

Starch is a mixture of two polysaccharides: amylose and amylopectin in a ratio of 10-20% by 80-90%. Amilose consists of residues, D-glucopyranosis, bound (14) -glyosoidal bonds. The macromolecule of amylase may include from 200 to 1000 residues of the total molecular weight of 160 thousand. units. (Angle24) Macromolecule amylose is cooled into a spiral, in the inner channel of which can be disposed of small sizes molecules, forming complexes that are called "inclusion connections", for example, the amylase complex with iodine has blue staining.

The structure of amylopectin.

Amylopectin - a homopolysaccharide of an extensive structure, as part of which a linear chain, D-glucopyranous residues was constructed by (14) glycosidic bonds, and branching elements are formed due to (16) glycosidic ties. Between 20 to 25 glucose residues are stacked between branching points; The molecular weight of amylopectin is approximately equal to 1-6ml. units. (Angle25)

Properties of Starch

Starch is a white amorphous substance, synthesized in plants in the process of photosynthesis and sparkling in tubers and seeds. The biochemical transformation is reduced to its hydrolysis. Hydrolysis in a living organism begins in the oral cavity under the action of saliva-amylase, where the starch is split to dextrins. Hydrolysis continues in the small intestine under the action of the pancreatic-amylase and ends with the formation of glucose molecules. The starch hydrolysis scheme may have the following form: (C 6 H 24 O 5) N + MN 2 O, dextrine-q n 2 o, F-hydrolysis of maltose + H 2 O, Maltaz N glucose molecules. Glucose from the intestine on the Male Vienna enters the liver, where he participates in the synthesis of glycogen, or blood is transferred to various organs and tissues, where he burns, highlighting energy. The level of glucose is normal amounts to 3.3-5.0 mmol / dm 3. High-quality reagent on starch and hydrolysis products is a solution of iodine. With starch, it forms a complex of dark blue. With dextrins - from violet to red-brown color. Maltose and glucose iodine is not stained with a solution.

G.likugen or animal starch

Glycogen is a structural and functional analogue of starch. It is contained in all animal fabrics, especially a lot in the liver (up to 20%) and muscles (up to 4%). The macromolecule of glycogen due to the large size does not pass through the membrane, but is inside the cell, i.e. In reserve until the need arises in energy. All activity processes are accompanied by mobilization of glycogen, i.e. Its hydrolytic splitting to glucose. Molecular weight of glycogen can reach 10-12 and even 1000 million. units. Macromolecule is based on the principle of amylopectin with the only difference that participating (16) glycosidic ties are more, i.e. Glycogen has a more extensive structure. The strong branching of the chain contributes to the performance of the energy function by the glycogen, because If there are a large number of terminal residues, the rapid cleavage of the desired number of glucose molecules is ensured. With a solution of glycogen iodine, gives color from the wine-red to brown.

TOpilot or cellulose

The fiber is a structural homopolysaccharide of plant origin, which is the basis of plant supporting tissues. The structural unit of fiber is, D-glucopyranosis, the links of which are connected (14) glycosidic bonds. The macromolecule has a linear structure and contains from 2.5 thousand. up to 12 thousand glucose residues with a total molecular weight of 1-2ml. Education scheme: (Angle26)

In and between chains, hydrogen bonds arise, which provide high mechanical strength, fiber, insoluability in water and chemical inertness of cellulose. Of the complex carbohydrates, only the fiber is not split into the small intestine due to the lack of some enzymes; In the thick intestine, it partially hydrolyzed under the action of microorganisms enzymes. In the process of digestion, the fiber acts as a ballast substance, improving the intestinal peristalsis.

G.ethteropolisaccharides

Hyaluronic acid. It is a connecting tissue polysaccharide. Its macromolecule is built from remnants of disaccharides, connected (14) glycosidic bonds. The disaccharide fragment includes the residues of D-glucuronic acid and N-acetyl-D-glucosamine, connected (13) glycoside. The molecular weight of the polymer reaches 2-7ml. Due to the large number of carboxyl groups of macromolecules, a large significant amount of water is associated, therefore, hyaluronic acid solutions are covered with increased viscosity. It is connected with its barrier function, which ensures the impermeability of the connective tissue for pathogenic bacteria. In the complex with polypeptides, hyaluronic acid is part of the vitreous body of the eye, the articular fluid, cartilage tissue.

G.licopean

Glycoproteins are mixed carbohydrate-containing biopolymers in which the protein molecule is associated with carbohydrates - oligosaccharides. Glycoproteins include enzymes, hormones, immunoglobulins and mucins. These complex substances belong to substances that determine the group specificity of the blood. They are based on a polypeptide chain to which oligosaccharide chains are joined (up to 55 beds). The carbohydrate component and the protein part are binding to a glycoside association with the participation of the hydroxyl groups of amino acids of the serine and threonine. The composition of the carbohydrate component includes N-acetyl-D-galactosamine, N-acetyl-D-glucosamine, D-galactose, which are located in a certain sequence from the uninstalled end of the oligosaccharide chain (in an amount of from 3 to 5). This sequence is called the determinant, it is it that determines the specificity of the blood group. The determinant monosaccharide of the blood group A is served by N-acetyl-D-galactozamine, and groups B - D-Galactose. With a change in determinants, blood type is changing.

Muzins - glycoproteins, in a non-chicken part of which contains glucosamine, sialic acid, N-acetyl-D-galactosamine and the residue of sulfuric acid. The word "Muzin" is formed from Greek mucos. - slime. Muzzins are part of saliva, egg protein, intestinal secrets and bronchi. Their presence in the solution provides high viscosity of the medium.

-amino acids. Peptides.

Amino acids can be considered as derivatives of carboxylic acids, in the molecule of which one of the hydrogen atoms is substituted with an amino group. The total number of amino acids reaches 300, but of them allocate a group of 20 of the most important-amino acids found in the composition of proteins of animal and vegetable origin.

The general formula has the form: (AK1)

The 1-acid center, the 2-main center, 1 and 2 make up the main fragment of the molecule, in which the chiral center is also isolated, 3 is a variable fragment of a molecule or a side chain.

All-amino acids with the exception of glycine (H 2 N-CH 2 -COOH) are optically active substances, because. Contain an asymmetric carbon atom and exist in the form of enantiomers. (AK2) in animal proteins contain L-amino acids; D-amino acids are found in microorganisms proteins. The side chain of amino acids has a specific composition and structure for each amino acid. In addition to hydrocarbon radicals, the side chain may contain functional groups (-on, -shh, -coh, -nh 2) and residues of heterocycles (five-membered cycle with 2 nitrogen). The composition of the side chain defines the main physico - chemical properties of amino acids and proteins:

1. Hydrophilicity - i.e. The ability of polar groups of the side chain to the formation of hydrogen bonds with water molecule is explained by the content of hydrophilic groups in the variable fragment (-on, -sh, -cooh, -nh 2, [-n \u003d], [-N (H) -]). The ability of amino acids to dissolve in water is the main factor with which the absorption of amino acids and their transportation in the body are associated. The hydrophobic groups of the side chain, which reduces the solubility, includes hydrocarbon radicals and benzene ring.

2. Side chain omogeneity, i.e. The ability to ionize in a hydrogen solution is explained by the presence in its composition of ionic groups dissociating by acid mechanism:

· -Son -COO - + H + (side chain acquires a negative charge)

· -Sh -S + H + (side chain acquires a negative charge)

by the main mechanism:

· -NH 2 + H + -NH 3 +

In an aqueous solution, the amino acids and proteins molecule are usually charged, and the presence of a charge in accordance with a stable hydrate sheath is an important factor determining the stability of the protein solution.

Acid-basic properties - amino acids

According to proteolytic theory of acids and bases, amino acids relate to ampholites, because Contains acid and main centers in the composition of the molecules. In an aqueous solution, the amino acid molecule exists in the form of a bipolar ion. (AK3) in highly acidic media: (pH \u003d 1-2) is formed a cationic form of amino acids. (AK4)

In a stronglyshtal medium: (pH \u003d 13-14) an anion form of amino acids prevails. (AK5)

There are pH values \u200b\u200bspecific for each amino acid in which the number of anionic forms in the solution is equal to the number of cationic forms. At the same time, it is necessary to take into account the presence of ionic groupings of the side chain. The pH value in which the overall charge of the amino acid molecule is 0, is called an amino acid isoelectric point (PI AK). If the pH of the solution corresponds to the isoelectric point of amino acid, then the molecule does not move during electrophoresis. If pH solutions pi, the anionic form of amino acid moves to the anode. This is based on the separation of amino acids by electrophoresis. For most animal proteins, electric dots lie in the range from 5.5 to 7.0 (exception: pepsin - pi \u003d 1, sylmin - pi \u003d 12), i.e. Proteins have more pronounced acid properties. In physiological values \u200b\u200bof pH \u003d 7.34-7.36 in vivo, no amino acid and no protein is in isoelectric state, but an anionic form dominates, a negative charge of which is equalized by sodium and potassium cations.

Chemical properties of amino acids

Amino acids are heterofunctional organic compounds that are in reactions typical of carbonyl groups, amino acids, and manifest a number of specific biochemical properties.

1. As ampholites, amino acids form salts when interacting with acids and bases (alanine with NaOH \u003d sodium salt of alanine; C HCl \u003d Solyasic acid alanine). (AK6)

2. Amino acid decarboxylation reaction is an enzymatic process of the formation of biogenic amines from the corresponding-amino acids. Decarboxylation occurs with the participation of the enzyme - decarboxylase and coenzyme - the peroxasal of phosphate. (AK7) ethanolamine is involved in the synthesis of phospholipids. (AK8) Histamine is a mediator of allergic reactions of the body. With decarboxylation of glutamic amino acid, GABA (gamma-amine-oil acid) is formed, which is a braking of the nervous system.

3. The demination reaction is this reaction is the process of removing the amino group by oxidative, reducing, hydrolytic or intramolecular deamination. The body prevails the path of oxidative deamination with the participation of enzymes - dehydrogenases and coenzyme - over +. At the first stage of the process, dehydrogenation is carried out with the formation of-amino acid. In the second stage, a non-enzymatic hydrolysis of amino acids occurs, which leads to the formation of -Betroxults and coming against the separation of ammonia, including the urea formation cycle. (AK9) With such processes, the level of amino acids in the cell decreases.

4. Reaminage or transamination of amino acid is the path of the synthesis of the necessary amino acids from -Basot. At the same time, the amino group is a-amino acid, which is in excess, and an amino-container-paper-acid (PVC, puck,-buck-oil acid). The process occurs with the participation of the enzyme - transaminase and coenzyme - the redest of phosphate. (AK10) The re-charge process will associate the exchange of proteins and carbohydrates in the body, it regulates the content of aminoilotes and synthesis of essential -aminoxot.

In addition to these reactions, amino acids are capable of forming esters, nitrogenated derivatives and to be bought in reactions that do not have analogies in in vitro chemistry. Such processes include phenylalanine hydroxylation in tyrosine. (AK11)

In the absence of the necessary enzyme in the body, phenylalanine accumulates, toxic acid is formed during its demination, the accumulation of which leads to a severe disease - phenylketonuria. The general property of the amino acid is the process of polycondensation, leading to the formation of peptides. As a result of this reaction, amide bonds are formed at the place of interaction of carbonyl groups of one amino acid and amino acid amino acids. In the peptides, this connection is called a peptide bond as part of the peptide group. (AK12)

The sequence of the amino acids in the composition of peptides and proteins determines their primary structure. If the polypeptide contains less than 100 residues of amino acids, then it is called peptide, more protein. At the place of peptide bonds of the protein molecule hydrolyzing in vivo with the participation of enzymes - peptidase. Among peptidases are distinguished:

· Endopeptidases, splitting connections inside macromolecule

· Exopeptidases that roll over nitrogen or carbon End amino acid

In the body, the proteins are split completely, because For vital activity, only free amino acids are needed. In vivo hydrolysis occurs in a strongly acidic or strong medium and is used to decipher protein composition. The composition of 1500 proteins is currently deciphered, including enzymes and hormones. For high molecular weight peptides and proteins, higher levels of the molecule organization are characterized, in the manifestation of their biochemical properties it is important to take into account the spatial structure, which is determined by the spatial structure of the peptide group. The peptide group refers to the p, p-conjugated system, as part of which atoms C, O and N lie in one-glossy. Due to the formation of a single delocalized 4P-electronic cloud, the rotation around C-N communication is difficult. At the same time, carbon units are in profitable location.

In 1950 Polneg and the Corn showed that the most favorable conformation of the polypeptide chain is human rights-held -spioral. The main contribution to the consolidation of this conformation of the chain is made by hydrogen bonds formed between parallel sections of peptide groups. Another one is known, the secondary structure of the protein: -thestructure in the form of a folded sheet. In addition to hydrogen bonds, the secondary structure is stabilized by disulfide bridges at the place of cysteine \u200b\u200bresidues.

The tertiary structure is a more complex spatial organization of macromolecules, which is stabilized by hydrogen bond, disulfide bridges, electrostatic interactions and van der Waals forces. In the tertiary structure, proteins are divided into:

· Globular - for them is characterized by a spinal structure laid in space in the form of a sphere - globules (for example, egg protein, an enzyme - globin in the composition of hemoglobin)

· Fibrillar - for them is characterized by a structure. As a rule, these proteins have a fibrous structure and they include muscle proteins, fabrics - Mioindozin, -Ceratin hair, colloidal connections.

Quaternary structure is known for some proteins that perform important physiological functions. For example, the Quaternary structure of the Globin is the spatial formation of 4 subunits, holding a friend near the friend's hydrophobic orientation bonds. It has been proven that it is the hemoglobin oxygen carrier can only in the presence of a quaternary structure of the globin.

ATagenial amino acids

Proteins are the basis of the structure and functions of living organisms, because Considerate the material basis of the chemical activity of the cell. All varieties of peptides and proteins are built from-amino acid residues, which are combined in the most different sequences, can form a huge amount of varied proteins. The total number of-amino acids included in their composition is close to 70. Among them, a group of 20 of the most important-amino acids that are constantly found in all proteins are distinguished.

Amino acids play an important role in the normal life of the body. The lack of individual amino acids leads to a violation of the metabolic processes. Thus, the lack of tryptophan causes a decrease in body weight, lysine deficiency - dizziness, nausea, increased sensitivity to noise. The lack of histidine is accompanied by a decrease in the concentration of hemoglobin. Recently, amino acids and their derivatives were widely used in medical practice, for example, methionine - in the treatment of a number of liver diseases, glutamic acid - in some brain lesions. Finally, a series of amino acids and their metabolic products have a regulating effect on many physiological functions of the body.

Amino acids - heteroofunctional compounds, which are derivatives of amino acids, in which one hydrogen atom in-carbon link is substituted for an amino group.

General formula-amino acids

Where coxy is an acid functional group, NH 2 is the main functional group, R radical (variable fragment), the dotted line is indicated by the total fragment of all -amino acids (except for the proline, in which this structure is part of the pyrrhimidine cycle), the asymmetric atom is marked (*) Carbon - chiral center.

For amino acids characterized by stereoisomeria. Asymmetric is a carbon atom, because Four different chemical groups are connected with it, in this case there are two possible configurations for each-amino acid - D- and L-enantiomers. In proteins there are only L-isomers of the amino acids. It is essential for the formation of the spatial structure of the protein and the manifestation of biological activity. This is directly connected by the stereospecificity of enzymes. As can be seen from the general formula, the amino acids differ from each other by the chemical nature of the radical (R), which is a group of atoms associated with carbon link and not participating in the formation of peptide bonds in the synthesis of protein. Therefore, all the multiple features of the structure and the function of protein bodies are associated with the chemical nature and the physicochemical properties of the-amino acid radicals. The most important - amino acids and characteristics of their side chains. The order of the name of amino acids: abbreviated; The structure of amino acids, the properties of the side chain.

1. Monoaminocarbonic:

- glycine (-amicoacetic, 2-amino ethanova); Gly; : hydrophobic, non-polar, non-ionic

- alanine (-amopropionic, 2-aminopropanova); Ala: hydrophobic, non-polar, non-ionic.

- Valin (-amino - methylmalassnaya, 2-amino-3-methylbutan); Shaft: hydrophobic, non-polar, non-ionic.

- leucine (-amino - methylvaleriah): lei; Hydrophobic, non-polar, non-ionic.

- Isoleucine (-Aino - methylvalerian): Ile: hydrophobic, non-polar, non-ionic.

2. Monoaminodicarbonic:

- Asparaginic (-aminyantic, 2-aminobutani); ASP: hydrophilic, polar, ionic (-sn 2 -coo -).

- glutamine (-aminoglutarovary, 2-aminoptadic); Glue: hydrophilic, polar, ionic (-sn 2 -coo -).

3. Diaminonocarbonic:

- lysine (, -daminocapron, 2,6-diaminoxane); Liz: hydrophilic, polar, ionic (-CH 2 -NH 3 +)

- Arginine (-amino - guanidicalarian); ARG: hydrophilic, polar, ionic (-CH 3 -NH-C (NH 2) \u003d NH 2 +).

4. Oxyamino acids:

- serine (-amino - oxypropionovaya); Ser: (AKM11) hydrophilic, polar, non-ionic

- Treonine (-amino - oxymalass) Tre: (AKM12) hydrophilic, polar, non-ionic

5. Serious:

- cysteine \u200b\u200b(-amino - thiopropion); CIS: (AKM13) hydrophilic, polar, ionic (-CH 2 -S -).

- cystine (di - amino - tiopropion (cystine derivative)); Cis-S-S-CIS: (AKM14) hydrophobic, non-polar, non-ionic.

- methionine (-amino - methylty-oil); Method: (AKM15) hydrophobic, non-polar, non-ionic.

6. Aromatic:

- phenylalanine (-amino - phenylpropionovaya); Hair dryer: (AKM16) hydrophobic, non-polar, non-ionic.

- tyrosine (-amino - pyraxiphenylpropionovaya); TIR: (AKM17) hydrophilic, polar, ionic (-sn 2 -C 6 H 4 -o -).

7. Heterocyclic:

- histidine (-amino - imidazolylpropiony); GIS: (AKM18) hydrophilic, polar, ionic

- tryptophan (-amino - indolyylpropiony); Three: (AKM19) hydrophobic, non-polar, non-ionic.

A special place among heterocyclic-amino acids occupy proline and its hydroxy derivatives, which are amino acids. They are in the amino acid fragment only in the pyramidine cycle.

Proline: Pro: (ACM20) hydrophobic, non-polar, non-ionic.

OxyProlin: OPR: (AKM21) hydrophobic, non-polar, non-ionic.

Aminosahara -the monosaccharides are formed, in the molecules of which the OH group of the second link is substituted with an amino group - NH 2, for example, D-glucosamine, D-galactosamine, D-mannosamine. In a water solution, they are in cyclic form: 2-amino-2-deoxy D-glucopyranosis, 2-amino-2-deoxy-d-galactopyranosis, 2-amino-2-deoxy-d-mannopyranosis.

The amino group is often acylated by the residue of acetic acid, while the amide group is formed: -NH-CO-, for example, N-acetyl-D-glucosamine (2-acetamide-2-deoxy-d-glucopyranosis).

Aminosahara is included in the group substances of blood, determining their specificity, and are components of structural polysaccharides.

Sugar acids are formed by oxidation of the primary hydroxyl group of monosaccharide. For example, during the oxidation of the primary hydroxyl group of glucose in the sixth carbon link, D-glucuronic acid is formed.

Control questions

1. Carbohydrates. Classification of hydrolysis ability.

2. Monosaccharides. Aldopenthosis. Aldogexose. Ketogexose. Structure. Isomeria. The concept of epimers.

3. Ring-chain tautomeria monosaccharides. Anomer.

4. Chemical properties of monosaccharides: properties of polyatomic alcohols; oxidation and recovery reactions; properties of semi-acetals; The response of esterification.

5. The structure of monosaccharide derivatives. Deoxyshara. Aminosahara.

Typical tasks

Task 1. Bring the structure of its diastereomers for α-D-glucopyranosis: anomer, enantiomer, s-2 epimer and epimer by C-4.

Decision: α-D-glucopyranosis - representative of hexosis. The hexose molecule contains several chiral centers, so it exists in the form of a large number of stereoisomers.

It is known that in the simplest case, when the molecule contains only one chiral center (glycerin aldehyde, lactic acid), it exists in the form of a pair of enantiomers belonging to each other as incompatible object object and its mirror image.

If there are two chiral centers in the molecule, the ability to exist diastereomers that differ in the configuration of a single chiral center appears. As an increase in the molecule, the number of chiral centers increases the total number of diastereomers with different configuration of one or more chiral centers.

In the chemistry of monosaccharides, diastereomers that differ in the configuration of only one carbon atom are called epimedes. At the same time, if we are talking about the difference in the configuration of the glycosidic (anomeric) carbon atom, then the diastereomers are called anomers. In aldosis, this carbon atom is C-1, ketosis - C-2. Anomers are a special occasion of epimers.

Stage 1. From the problem above, the title of the compound is seen that the D-glucose molecule is located in a six-membered cyclic (pyranous) form in the form of an α-anomer.

In the α-anomer D-glucopyranosis, the C-1 carbon atom has a configuration that coincides with the configuration of its "terminal" C-5 chiral center, i.e. Atom that determines the belonging to the stereochemical row. When writing stereochemical carbohydrate formulas, the C-1 configuration in the α-anomer is depicted in such a way that the semi-acetal hydroxyl group in the heuorce formula is located under the plane of the pyranous cycle, in the conformational formula it occupies an axial position.

Another D-glucopyranose anomer (β-anomer) differs from the considered α-anomer with the opposite configuration of the chiral carbon atom C-1. Accordingly, a semi-acetal hydroxyl group in a β-anomer is located above the plane of the pyranous cycle in the Heuorce formula and occupies an equatorial position in the conformational formula:

Stage 2. α-D-glucopyranosis is one of two enantiomers, namely an enantiomer belonging to the D-stereochemical row. Belonging to D-row means that the configuration of the most remote from the oxo group of an asymmetric (chiral) carbon atom coincides with the configuration of the D-glycerin aldehyde chiral center (configuration standard).

Another enantiomer is a mirror image of the α-D-glucopyranosis molecule and refers to L-stereochemical row. In L-glucose, the configuration of the chiral atoms C-2, C-3, C-4, C-5 is opposite to the configuration of these atoms in D-glucose. We write the structure of enantiomers glucose in an open form:

In the cyclic (pyranous) form in that other enantiomer, an additional center of chirality occurs - an anomeric C-1 carbon atom. Then the α-anneer D-glucopyranose will correspond to the enantiomer L-series, having the opposite configuration of all chirality centers, including C-1. Based on this condition, the semi-acetal ON-group of the enantiomer L-row should be located in the Heuores formula above the plane of the pyranous cycle. In this case, the configuration of an anomeric C-1 carbon atom in the L-glucopyranose molecule coincides with the configuration of its Hi-5 chiral center, which determines the belonging to the stereochemical row, i.e. Enantiomer is in α-form. Consequently, the enantiomer with respect to α-D-glucopyranosis is β-l-glucopyranosis.

Stage 3.. The epimer of D-glucose, differing from it with the C-2 configuration, is a D-mannose, and an epimer that is characterized by C-4 - D-Galactose configuration:

Based on the fact that epimers differ in the configuration of only one chiral carbon atom, D-mannose and D-galactose in cyclic form should differ from D-glucose with the C-2 and C-4 configuration, and the configuration of the resulting chiral carbon atom 1 should be the same in all three epimers. Thus, with respect to α-D-glucopyranosis, the epimir of C-2 is the α-D-mannopyranosis, and the epimer of the C-4 - α-D-galactopyranosis:

Conclusion. The ratio between the above stereoisomers α-D-glucopyranose can be represented as the following scheme:

Enantiomers α, L-glucopian

According to C 1 (anomer) β, d-glucopyranosis

α, D-glucopyranoz epimers with 2 α, D-mannopopiranosis

Diastereomers

Task 2. What biologically important products can be obtained during oxidation of D-glucose in various conditions?

Decision.D-glucose is a heteroofunctional compound containing at the same time hydroxyl and aldehyde functional groups. Both groups, especially aldehyde, are able to oxidize, and the result of oxidation is to turn them into a carboxyl group.

Stage 1. When oxidizing in neutral or weakly acid medium, the D-glucose molecule is not destructive. As an oxidizing agent, a solution of bromine in water, a talense reagent or freshly prepared copper hydroxide (II) during heating is used.

In general, the reaction can be represented as selective oxidation of the aldehyde group into carboxyl without affecting hydroxyl groups:

The medicine uses a calcium gluconic salt (calcium gluconate).

Stage 2. In a strong-acid medium in a D-glucose molecule, not only an aldehyde, but also a primary alpit group is oxidized. At the same time, a two-mine D-glucaric acid is formed. As a rule, nitric acid is used as an oxidant.

D.-glucose D.-Hlucaric acid

Stage 3. One more case of the oxidation of terminal carbon d-glucose atoms can be represented when the aldehyde group is preserved, and only the primary-pic group is oxidized. In this case, D-glucuronic acid is obtained.

D-glucuronic acid cannot be obtained by direct oxidation of D-glucose. The pre-aldehyde group D-glucose is protected by turning it into a glycoside, and only then oxidizing the primary stroke group:

An important biological role of D-glucuronic acid is that many toxic substances are allocated with urine as glucuronides (detoxification).

Conclusion. When oxidizing D-glucose, depending on the conditions, D-glucon, D-glucar and D-glucuronic acid can be obtained.

Task 3. As a result of fermentation of D-glucose, a product was formed, which reacts with alkali only in a molar ratio of 1: 1 and may be acylated. Suppose what kind of fermentation has occurred and write the schemes of all reactions.

Decision.The most famous types of fermentation of D-glucose: alcohol, lactic acid, oily acid and lemon-acid. Ethanol does not react with alkali, oil acid is not acylated, and citric acid reacts with alkali in the ratio of 1: 3. Consequently, milk acid is a possible fermentation product:

Indeed, lactic acid reacts with alkali in a 1: 1 ratio:

and may be undergoing acylation on the hydroxyl group:

Test tasks for self-control

Physico-chemical properties of carbohydrates. Monosaccharides are solid crystalline substances that are well soluble in water, poorly soluble in alcohol and ether. Various monosaccharides differ significantly by the degree of sweetness on organoleptic evaluation. If we take conditionally sweetness of sucrose for 100%, then fructose in the same amount is much more sweet - 173%, glucose-less sweet - 74%, xylose - 40%. The most "unsweetened" sugar-lactose. Its sweetness in the same quantity is only 16% of the sweetness of sucrose.
Concentrated acids dehydrating monosaccharides and as a result of cyclic aldehydes - Furfurali:

Furfurali formed can enter with phenols or their derivatives in the condensation reaction to the formation of painted products, the quantitative determination of monosaccharides (phenol and acid method with spectrophotometric end) is based on this. Free monosaccharides are absorbed in the ultraviolet very weakly and only with a wavelength of 195 nm, that is, in the nonspecific region. Therefore, their direct determination by spectral methods is very difficult. When the monosaccharides are heated with dilute alkalishes, the polycondensation reactions also come into the formation of painted products (the method of quantifying sugars in the urine along Althausen).

Oxidation of sugars. When exposed to various oxidants, various sugarcic acids (glycaric, glyacon or glycurial) can be obtained:

In the form of acids, monosaccharide units may occur in natural polymers (pectin).

Restoration of Sakharov. As a result of the restoration of monosaccharides, polyatomic alcohols are formed. When the glucose is restored, it turns out sorbitol, when restoring the mannon, and when the fructose is restored, sorbitol and mannitol are formed at the same time:

Monosaccharides are found in nature both in pure form and as part of the so-called glycosides, as a result of the formation of communication with molecules of almost any organic compounds through their hydroxyl group. The glycosides, thus, consist of a carbohydrate component (sugar) and a nonachar part called aglikon. Glycosida structure salicin (2-hydroxymethyl) -phenyl-b-d-glucofuranoside) is shown below:

A semi-acetal hydroxyl (synonymous glycoside hydroxyl, anomeric hydroxyl) is involved from the carbohydrate in the formation of communication (synonymous hydroxyl), on the side of the aglikon, any hydroxyl. We remind you that the glycosidoid hydroxyl in carbohydrates has sharply different properties from the remaining hydroxyl groups. In particular, it easily enters into the reaction of the formation of complete acetals catalyzed by acids.

Finally, quite often carbohydrates are present (especially in polymers) in the form of nitrogen derivatives, when the hydroxyl group in the second carbon atom is replaced with an amino group. Almost always this amino group is acetylated.