• Domestic science and medicine in the 19th - early 20th centuries Chemistry of the 19th century in medicine
• What are peptides? Types and types of peptides. All about peptides and anti-aging cosmetics with peptides Additional peptides are not formed
• Toxic effect on humans of hazardous chemicals
• Radioautography Method of autoradiography in cytology
• Identification of bacteria by antigenic structure
• Organic matter in wastewater What are organic compounds in water
• Hydrogen index (pH factor)
• What is the pH of water and why is it important to know it?
• Redox potential Redox systems
• Reversible redox system Reversible redox systems

The sources of saturated hydrocarbons are oil and natural gas. The main component of natural gas is the simplest hydrocarbon, methane, which is used directly or processed. Oil extracted from the bowels of the earth is also subjected to processing, rectification, and cracking. Most hydrocarbons are obtained from the processing of oil and other natural resources. But a significant amount of valuable hydrocarbons is obtained artificially, synthetic ways.

Isomerization of hydrocarbons

The presence of isomerization catalysts accelerates the formation of branched hydrocarbons from linear hydrocarbons. The addition of catalysts makes it possible to somewhat reduce the temperature at which the reaction proceeds.
Isooctane is used as an additive in the production of gasoline, to improve their anti-knock properties, and also as a solvent.

Hydrogenation (hydrogen addition) of alkenes

As a result of cracking, a large amount of unsaturated hydrocarbons with a double bond, alkenes, is formed. Their number can be reduced by adding hydrogen to the system and hydrogenation catalysts- metals (platinum, palladium, nickel):

Cracking in the presence of hydrogenation catalysts with the addition of hydrogen is called reduction cracking. Its main products are saturated hydrocarbons. Thus, the increase in pressure during cracking ( high pressure cracking) allows you to reduce the amount of gaseous (CH 4 - C 4 H 10) hydrocarbons and increase the content of liquid hydrocarbons with a chain length of 6-10 carbon atoms, which form the basis of gasoline.

These were industrial methods for obtaining alkanes, which are the basis for the industrial processing of the main hydrocarbon raw material - oil.

Now consider several laboratory methods for obtaining alkanes.

Decarboxylation of sodium salts of carboxylic acids

Heating the sodium salt of acetic acid (sodium acetate) with an excess of alkali leads to the elimination of the carboxyl group and the formation of methane:

If instead of sodium acetate we take sodium propionate, then ethane is formed, from sodium butanoate - propane, etc.

Wurtz synthesis

When haloalkanes react with an alkali metal sodium, saturated hydrocarbons and an alkali metal halide are formed, for example:

The action of an alkali metal on a mixture of halogen hydrocarbons (for example, bromoethane and bromomethane) will lead to the formation of a mixture of alkanes (ethane, propane and butane).

!!! The Wurtz synthesis reaction leads to an elongation of the chain of saturated hydrocarbons.

The reaction on which the Wurtz synthesis is based proceeds well only with haloalkanes, in the molecules of which the halogen atom is attached to the primary carbon atom.

Hydrolysis of carbides

When processing some carbides containing carbon in the -4 oxidation state (for example, aluminum carbide), methane is formed with water.

The reactions of carboxylic acids can be divided into several large groups:

1) Recovery of carboxylic acids

2) Decarboxylation reactions

3) Substitution reactions at the -carbon atom of carboxylic acids

4) Reactions of nucleophilic substitution at the acyl carbon atom.

We will consider each of these groups of reactions in turn.

18.3.1. Recovery of carboxylic acids

Carboxylic acids are reduced to primary alcohols with lithium aluminum hydride. The reduction takes place under more severe conditions than is required for the reduction of aldehydes and ketones. Recovery is usually carried out by boiling in a solution of tetrahydrofuran.

Diborane B 2 H 6 also reduces carboxylic acids to primary alcohols. The reduction of the carboxyl group to CH 2 OH by the action of diborane in THF is carried out under very mild conditions and does not affect some functional groups (NO 2 ; CN;
), so this method in some cases is preferable.

18.3.2. Decarboxylation

This term combines a whole group of diverse reactions in which CO 2 is eliminated and the resulting compounds contain one carbon atom less than the original acid.

The most important of the decarboxylation reactions in organic synthesis is the Borodin-Hunsdiecker reaction, in which the silver salt of a carboxylic acid is converted to an alkyl halide when heated with a solution of bromine in CCl 4 .

Successful carrying out of this reaction requires the use of carefully dried silver salts of carboxylic acids, and the yield of the alkyl halide varies widely depending on the degree of purification and dehydration of the salt. This drawback is devoid of modification, where mercury salts are used instead of silver. The mercury salt of a carboxylic acid is not isolated individually, but a mixture of carboxylic acid, yellow mercury oxide and halogen is heated in an indifferent solvent. This method generally results in a higher and more reproducible output.

A radical chain mechanism has been established for the Borodin-Hunsdiecker reaction. The acyl hypobromite formed in the first stage undergoes homolytic cleavage with the formation of a carboxyl radical and a bromine atom. The carboxyl radical loses CO 2 and turns into an alkyl radical, which then regenerates the chain by splitting off a bromine atom from the acyl hypobromite.

Circuit initiation:

Chain development:

The original method of oxidative decarboxylation of carboxylic acids was proposed by J. Kochi in 1965. Carboxylic acids are oxidized with lead tetraacetate, decarboxylation occurs and, depending on the conditions, alkanes, alkenes or acetic acid esters are obtained as reaction products. The mechanism of this reaction has not been established in detail; the following sequence of transformations is assumed:

The alkene and ester appear to be formed from the carbocation, respectively, by proton elimination or acetate ion capture. The introduction of a halide ion into the reaction mixture almost completely suppresses both these processes and leads to the formation of alkyl halides.

These two decarboxylation methods complement each other well. Decarboxylation of Ag or Hg salts gives the best results for carboxylic acids with a primary radical, while oxidation with lead tetraacetate in the presence of lithium chloride gives the highest yields of alkyl halides for carboxylic acids with a secondary radical.

Another reaction of decarboxylation of carboxylic acids, which is of great preparative importance, is the electrolytic condensation of salts of carboxylic acids, discovered in 1849 by G. Kolbe. He carried out the electrolysis of an aqueous solution of potassium acetate in the hope of obtaining a free radical CH 3 , but instead of it, ethane was obtained at the anode. Similarly, during the electrolysis of an aqueous solution of the sodium salt of valeric acid, n.octane was obtained instead of the butyl radical. The electrochemical oxidation of carboxylate ions turned out to be historically the first general method for the synthesis of saturated hydrocarbons. During the electrolysis of sodium or potassium salts of saturated aliphatic acids in methanol or aqueous methanol in an electrolyzer with platinum electrodes at 0–20°C and with a sufficiently high current density, alkanes are formed with a yield of 50–90%.

However, in the presence of an alkyl group in the -position, the yields are sharply reduced and rarely exceed 10%.

This reaction proved to be particularly useful for the synthesis of diesters of dicarboxylic acids ROOC(CH 2) n COOR with n from 2 to 34 in the electrolysis of alkali salts of half-esters of dicarboxylic acids.

In modern organic electrosynthesis, cross electrolytic condensation is widely used, which consists in the electrolysis of a mixture of carboxylic acid salts and a dicarboxylic acid monoester.

The electrolysis of a solution of these two salts results in the formation of a mixture of three very different reaction products, which can be easily separated by distillation into their individual components. This method allows you to lengthen the carbon skeleton of a carboxylic acid by any number of carbon atoms in almost one operation.

Electrolytic condensation is limited to straight-chain carboxylic acid salts and dicarboxylic acid half-ester salts. Salts of ,- and ,-unsaturated acids do not undergo electrochemical condensation.

For the Kolbe reaction, a radical mechanism was proposed, including three successive stages: 1) oxidation of carboxylate ions at the anode to carboxylate radicals
; 2) decarboxylation of these radicals to alkyl radicals and carbon dioxide; 3) recombination of alkyl radicals.

At a high current density, a high concentration of alkyl radicals at the anode promotes their dimerization; at a low current density, alkyl radicals either disproportionate to form an alkene or alkane or abstract a hydrogen atom from the solvent.

Salts of carboxylic acids also undergo decarboxylation during pyrolysis. Once upon a time, pyrolysis of calcium or barium salts of carboxylic acids was the main method for obtaining ketones. In the 19th century, the “dry distillation” of calcium acetate was the main method for producing acetone.

Subsequently, the method was improved in such a way that it does not include the stage of obtaining salts. Vapors of carboxylic acid are passed over the catalyst - oxides of manganese, thorium or zirconium at 380-400 0 . The most efficient and expensive catalyst is thorium dioxide.

In the simplest cases, acids with two to ten carbon atoms are converted into symmetrical ketones with a yield of about 80% when boiled with powdered iron at 250-300 . This method finds application in industry. The pyrolytic method is most successfully used and is currently used for the synthesis of five- and six-membered cyclic ketones from dibasic acids. For example, from a mixture of adipic acid and barium hydroxide (5%) at 285-295 , cyclopentanone is obtained with a yield of 75-85%. Cyclooctanone is formed from azelaic acid when heated with ThO 2 with a yield of no more than 20%; this method is not very suitable for obtaining cycloalkanones with a large number of carbon atoms.

DECARBOXYLATION, elimination of CO 2 from the carboxyl group of carboxylic acids or the carboxylate group of their salts. It is usually carried out by heating in the presence of acids or bases. The decarboxylation of saturated monocarboxylic acids proceeds, as a rule, under harsh conditions. Thus, the calcination of Na acetate with an excess of soda lime leads to the elimination of CO 2 and the formation of methane: CH 3 COONa + NaOH CH 4 + Na 2 CO 3. DECARBOXYLATION is facilitated for acids containing a -position of electronegative groups. Easy DECARBOXYLATION of acetoacetic (formula I) and nitroacetic acids (II) is due to the occurrence of a cyclic transition state:


D. homologues of nitroacetic acid - a preparative method for obtaining nitroalkanes. Naib. DECARBOXYLATION of acids is easily carried out, the carboxyl group of which is directly connected with other electrophores. groups. For example, heating pyruvic acid with conc. H 2 SO 4 easily leads to acetaldehyde:

During the decarboxylation of oxalic acid under the same conditions, in addition to CO 2, H 2 O and CO are formed. D. is also facilitated if the carboxyl group is bonded to an unsaturated C atom; so, DECARBOXYLATION of the monopotassium salt of acetylenedicarboxylic acid is a convenient method for the synthesis of propiolic acid:

D. acetylenecarboxylic acid is carried out at room temperature in the presence. Cu salts: HCCCOOH HC=CH + CO 2 . Aromatic acids are decarboxylated, as a rule, under harsh conditions, for example, when heated in quinoline in the presence of a metal. powders. By this method, in the presence of Cu, furan is obtained from pyromucic acid. Decarboxylation of aromatic acids is facilitated in the presence of electrophoresis. substituents, for example, trinitrobenzoic acid is decarboxylated when heated to 40-45 °C. D. carboxylic acid vapors over heated catalysts (Ca and Ba carbonates, Al 2 O 3, etc.) - one of the methods for the synthesis of ketones: 2RCOOH: RCOR + H 2 O + CO 2 . When decarboxylation of a mixture of two acids, a mixture of unsymmetrical and symmetrical ketones is formed. DECARBOXYLATION of sodium salts of carboxylic acids during the electrolysis of their conc. aqueous solutions (see Kolbe reactions) is an important method for obtaining alkanes. DECARBOXYLATION reactions that have preparative significance include halogen decarboxylation - the replacement of a carboxyl group in a molecule by a halogen. The reaction proceeds under the action of LiCl (or N-bromosuccinimide) and tetraacetate Pb on carboxylic acids, as well as free halogens (Cl 2, Br 2, I 2) on salts of carboxylic acids, for example: RCOOM RHal (M = Ag, K, Hg, T1). Silver salts of dicarboxylic acids under the action of I 2 are easily converted into lactones:


Oxidize also plays an important role. DECARBOXYLATION - elimination of CO 2 from carboxylic acids, accompanied by oxidation. Depending on the oxidizing agent used, this DECARBOXYLATION results in alkenes, esters, and other products. So, during the decarboxylation of phenylacetic acid in the presence of pyridine-N-oxide, benzaldehyde is formed:

Like DECARBOXYLATION of salts of carboxylic acids, DECARBOXYLATION of organoelement derivatives and esters occurs, for example:


D. esters are also carried out under the action of bases (alcoholates, amines, etc.) in an alcoholic (aqueous) solution or Li and Na chlorides in DMSO. Of great importance in various metabolic processes is enzymatic DECARBOXYLATION. There are two types of such reactions: simple DECARBOXYLATION (reversible reaction) and oxidative DECARBOXYLATION, in which first DECARBOXYLATION occurs, and then dehydrogenation of the substrate. According to the latter type, in the organism of animals and plants, enzymatic decarboxylation of pyruvic and a -ketoglutaric acids - intermediate products of the breakdown of carbohydrates, fats and proteins (see Tricarboxylic acid cycle). Enzymatic decarboxylation of amino acids is also widespread in bacteria and animals.

Chemical encyclopedia. Volume 2 >>

The reactions of carboxylic acids can be divided into several large groups:

1) Recovery of carboxylic acids

2) Decarboxylation reactions

3) Substitution reactions at the -carbon atom of carboxylic acids

4) Reactions of nucleophilic substitution at the acyl carbon atom.

We will consider each of these groups of reactions in turn.

18.3.1. Recovery of carboxylic acids

Carboxylic acids are reduced to primary alcohols with lithium aluminum hydride. The reduction takes place under more severe conditions than is required for the reduction of aldehydes and ketones. Recovery is usually carried out by boiling in a solution of tetrahydrofuran.

Diborane B 2 H 6 also reduces carboxylic acids to primary alcohols. The reduction of the carboxyl group to CH 2 OH by the action of diborane in THF is carried out under very mild conditions and does not affect some functional groups (NO 2 ; CN;
), so this method in some cases is preferable.

18.3.2. Decarboxylation

This term combines a whole group of diverse reactions in which CO 2 is eliminated and the resulting compounds contain one carbon atom less than the original acid.

The most important of the decarboxylation reactions in organic synthesis is the Borodin-Hunsdiecker reaction, in which the silver salt of a carboxylic acid is converted to an alkyl halide when heated with a solution of bromine in CCl 4 .

Successful carrying out of this reaction requires the use of carefully dried silver salts of carboxylic acids, and the yield of the alkyl halide varies widely depending on the degree of purification and dehydration of the salt. This drawback is devoid of modification, where mercury salts are used instead of silver. The mercury salt of a carboxylic acid is not isolated individually, but a mixture of carboxylic acid, yellow mercury oxide and halogen is heated in an indifferent solvent. This method generally results in a higher and more reproducible output.

A radical chain mechanism has been established for the Borodin-Hunsdiecker reaction. The acyl hypobromite formed in the first stage undergoes homolytic cleavage with the formation of a carboxyl radical and a bromine atom. The carboxyl radical loses CO 2 and turns into an alkyl radical, which then regenerates the chain by splitting off a bromine atom from the acyl hypobromite.

Circuit initiation:

Chain development:

The original method of oxidative decarboxylation of carboxylic acids was proposed by J. Kochi in 1965. Carboxylic acids are oxidized with lead tetraacetate, decarboxylation occurs and, depending on the conditions, alkanes, alkenes or acetic acid esters are obtained as reaction products. The mechanism of this reaction has not been established in detail; the following sequence of transformations is assumed:

The alkene and ester appear to be formed from the carbocation, respectively, by proton elimination or acetate ion capture. The introduction of a halide ion into the reaction mixture almost completely suppresses both these processes and leads to the formation of alkyl halides.

These two decarboxylation methods complement each other well. Decarboxylation of Ag or Hg salts gives the best results for carboxylic acids with a primary radical, while oxidation with lead tetraacetate in the presence of lithium chloride gives the highest yields of alkyl halides for carboxylic acids with a secondary radical.

Another reaction of decarboxylation of carboxylic acids, which is of great preparative importance, is the electrolytic condensation of salts of carboxylic acids, discovered in 1849 by G. Kolbe. He carried out the electrolysis of an aqueous solution of potassium acetate in the hope of obtaining a free radical CH 3 , but instead of it, ethane was obtained at the anode. Similarly, during the electrolysis of an aqueous solution of the sodium salt of valeric acid, n.octane was obtained instead of the butyl radical. The electrochemical oxidation of carboxylate ions turned out to be historically the first general method for the synthesis of saturated hydrocarbons. During the electrolysis of sodium or potassium salts of saturated aliphatic acids in methanol or aqueous methanol in an electrolyzer with platinum electrodes at 0–20°C and with a sufficiently high current density, alkanes are formed with a yield of 50–90%.

However, in the presence of an alkyl group in the -position, the yields are sharply reduced and rarely exceed 10%.

This reaction proved to be particularly useful for the synthesis of diesters of dicarboxylic acids ROOC(CH 2) n COOR with n from 2 to 34 in the electrolysis of alkali salts of half-esters of dicarboxylic acids.

In modern organic electrosynthesis, cross electrolytic condensation is widely used, which consists in the electrolysis of a mixture of carboxylic acid salts and a dicarboxylic acid monoester.

The electrolysis of a solution of these two salts results in the formation of a mixture of three very different reaction products, which can be easily separated by distillation into their individual components. This method allows you to lengthen the carbon skeleton of a carboxylic acid by any number of carbon atoms in almost one operation.

Electrolytic condensation is limited to straight-chain carboxylic acid salts and dicarboxylic acid half-ester salts. Salts of ,- and ,-unsaturated acids do not undergo electrochemical condensation.

For the Kolbe reaction, a radical mechanism was proposed, including three successive stages: 1) oxidation of carboxylate ions at the anode to carboxylate radicals
; 2) decarboxylation of these radicals to alkyl radicals and carbon dioxide; 3) recombination of alkyl radicals.

At a high current density, a high concentration of alkyl radicals at the anode promotes their dimerization; at a low current density, alkyl radicals either disproportionate to form an alkene or alkane or abstract a hydrogen atom from the solvent.

Salts of carboxylic acids also undergo decarboxylation during pyrolysis. Once upon a time, pyrolysis of calcium or barium salts of carboxylic acids was the main method for obtaining ketones. In the 19th century, the “dry distillation” of calcium acetate was the main method for producing acetone.

Subsequently, the method was improved in such a way that it does not include the stage of obtaining salts. Vapors of carboxylic acid are passed over the catalyst - oxides of manganese, thorium or zirconium at 380-400 0 . The most efficient and expensive catalyst is thorium dioxide.

In the simplest cases, acids with two to ten carbon atoms are converted into symmetrical ketones with a yield of about 80% when boiled with powdered iron at 250-300 . This method finds application in industry. The pyrolytic method is most successfully used and is currently used for the synthesis of five- and six-membered cyclic ketones from dibasic acids. For example, from a mixture of adipic acid and barium hydroxide (5%) at 285-295 , cyclopentanone is obtained with a yield of 75-85%. Cyclooctanone is formed from azelaic acid when heated with ThO 2 with a yield of no more than 20%; this method is not very suitable for obtaining cycloalkanones with a large number of carbon atoms.

Decarboxylation

The decarboxylation reaction of carboxylic acids consists in the elimination of a carboxyl group from a carboxylic acid molecule, proceeding according to the following general scheme:

R-C(O)OH --> R-H + CO 2

The most well-known reactions are the decarboxylation of acetic and benzoic acids, which are carried out by heating a mixture of a salt of a carboxylic acid and an alkali to a high temperature:

H 3 C-C (O) ONa + NaOH --> CH 4 + Na 2 CO 3

Ph-C(O)ONa + NaOH --> PhH + Na 2 CO 3

A number of acids decarboxylate very easily with slight heating, in general, the presence of electroacceptor substituents in the organic radical of the carboxylic acid facilitates the decarboxylation reaction, for example, nitromethane and trinitrobenzene are obtained from nitroacetic and trinitrobenzoic acids, respectively:

O 2 N-CH 2 -C (O) OH --> O 2 N-CH 3 + CO 2

2,4,6-(NO 2) 3 C 6 H 2 -C(O)OH ---> 1,3,5-(NO 2) 3 C 6 H 3 + CO 2.

Decarboxylation at relatively low temperatures is a feature of aromatic carboxylic acids, in the aromatic ring of which hydroxyl groups are in the ortho- or para-position, for example, gallic acid easily turns into trihydric phenol - pyrogallol with slight heating.

Acetoacetic and malonic acids are very easily decarboxylated:

H 3 C-C(O)-CH 2 -C(O)OH --> H 3 C-C(O)-CH 3 + CO 2

HO-C(O)-CH 2 -C(O)OH --> H 3 С-C(O)OH + CO 2

The latter reaction is the basis of convenient preparative synthesis methods, called "Synthesis based on malonic and acetoacetic esters".

Decarboxylation of dicarboxylic acids is used to obtain cyclic ketones, for example, heating adipic acid with a small amount of barium oxide allows cyclopentanone to be obtained in good yield:

HO-C (O) - (CH 2) 4 -C (O) OH --> cyclo-C 4 H 8 C \u003d O + CO 2

The decarboxylation reaction is a key step in reactions such as the Kolbe (electrolysis of salts of carboxylic acids), Simonini, Marquewald, Dakin-West and Borodin-Hunsdiecker reactions.

Oxidative decarboxylation. When heated to 260-300 o With the copper salt of benzoic acid, it decomposes with the formation of phenyl benzoate, carbon dioxide and copper:

2 Cu --> C 6 H 5 -C (O) O-C 6 H 5 + CO 2 + Cu

The reaction proceeds through a cyclic intermediate state. One option for oxidative decarboxylation is the reaction of carboxylic acids with lead tetraacetate (oxidant) in the presence of calcium or lithium chloride (source of chloride anions). The reaction proceeds in boiling benzene and leads to the formation of halogen derivatives of hydrocarbons:

R-C(O)-OH + Pb 4 + 2 LiCl --> R-Cl + Pb 2 + CH 3 C(O)OLi + CH 3 C(O)OH

Decarboxylation reactions are integral and important stages of such biochemical processes as alcoholic fermentation and tricarboxylic acid cycle.

Links

Literature

• K. V. Vatsuro, Mishchenko “Nominal reactions in organic chemistry”, M .: Chemistry, 1976.
• J. J. Lee, Nominal reactions. Mechanisms of organic reactions, M.: Binom., 2006.

Wikimedia Foundation. 2010 .

See what "Decarboxylation" is in other dictionaries:

Cleavage of CO2 from the carboxyl group of carboxylic acids to t. Enzymatic D. can be reversible (for example, D. of oxaloacetate with the formation of pyruvate) and irreversible (for example, oxidative D. of amino acids catalyzed by decarboxylases, coenzyme to ryh ... Biological encyclopedic dictionary

Cleavage of CO2 from the carboxyl group of carboxylic acids is usually with the participation of decarboxylase enzymes. Enzymatic D. can be reversible (D. oxaloacetate to pyruvate) and irreversible (oxidative D. amino acids). Special meaning in the cell ... ... Dictionary of microbiology

- [de ... + lat. carbo charcoal + gr. sour] - cleavage from organic acids of the COOH group; is essential in the process of metabolism and during decay. A large dictionary of foreign words. Publishing house "IDDK", 2007 ... Dictionary of foreign words of the Russian language

Exist., Number of synonyms: 1 split (8) ASIS Synonym Dictionary. V.N. Trishin. 2013 ... Synonym dictionary

The process of splitting off carbon dioxide from the carboxyl group (see Carboxyl) of acids. In the absence of other non-hydrocarbon gr. in the D. molecule leads to the formation of hydrocarbons. Many hypotheses of the origin of oil attach great importance to participation in ... ... Geological Encyclopedia

decarboxylation- The reaction of splitting off the CO2 group from the carboxyl group of carboxylic acids or the carboxylate group of their salts. [Arefiev V.A., Lisovenko L.A. English Russian explanatory dictionary of genetic terms 1995 407s.] Topics genetics EN decarboxylation ... Technical Translator's Handbook

Decarboxylation- * decarboxylation * decarboxylation movement or loss by organic compounds of carboxyl groups, from which CO2 is formed. D. occurs under the action of decarboxylase enzymes that catalyze the roar of 51 positions to deoxyribose instead of ... ... Genetics. encyclopedic Dictionary

Decarboxylation decarboxylation. The reaction of elimination of the CO2 group from the carboxyl group of carboxylic acids or the carboxylate group of their salts. (

• Activities and pedagogical views of Jan Amos Comenius
• The rate constant is calculated by the formula Rate constant value
• Phase diagrams of two-component systems "polymer - solvent" Phase diagrams of two-component systems "polymer - solvent"
• Fine and hyperfine structure of optical spectra
• How to learn chemistry on your own from scratch: effective ways
• Properties and characteristics of alkenes
• Characteristics of a student from the place of internship
• Characteristics for a student who had an internship at an enterprise: writing rules
• Biography of Faraday. Great scientists. Michael Faraday. discovery of electromagnetic rotation
• Modern innovations in education

• Substituents on the benzene ring are divided into two groups Reactions of the benzene ring
• Types of chemical reactions in organic chemistry Electrophilic addition reactions
• Methods for separating heterogeneous mixtures
• Polymethacrylic acid
• General characteristics of the elements of the VI A subgroup Elements 6a of the subgroup
• Theoretical foundations of physics
• Graph theory in chemistry. graph theory. Basic definitions and theorems of graph theory
• Algebra and harmony in chemical applications
• Tests on the course "Ecology and nature management
• WWF Russia Director Igor Chestin: Yakutia is among the leaders I know that you travel a lot… Why do you need this