Or Kolbe process(named after Adolf Wilhelm Hermann Kolbe and Rudolf Schmitt) is a chemical reaction of sodium phenolate carboxylation by the action of carbon dioxide under severe conditions (pressure 100 atm., temperature 125 ° C) followed by treatment of the product with acid. In industry, this reaction is used to synthesize salicylic acid, which is a precursor of aspirin, as well as β-hydroxy naphthoic and other acids. A review article was devoted to the Kolbe - Schmitt reaction and its application.
Reaction mechanism
The key stage in the Kolbe - Schmitt reaction mechanism is the nucleophilic addition of the phenolate ion to carbon dioxide, which leads to the formation of the corresponding salicylate.
The direction of the reaction depends on which phenolate is used as the starting compound. When sodium phenolate is introduced into the reaction, ortho-substituted product. This is because the sodium ion is able to stabilize the six-membered transition state, from which the electrophilic attack of the aromatic ring of phenol occurs. When potassium phenolate is used, the formation of a six-membered transition complex is less favorable, and therefore pair-substituted product.
The reaction is facilitated by the presence of electron donor substituents, for example, polyatomic phenols (phloroglucinol, resorcinol, pyrocatechol) are carboxylated in an aqueous solution of potassium carbonate.
An industrial version of the Kolbe - Schmitt reaction, used for the synthesis of salicylic acid and its derivatives (p-amino, 5-chlorosalicylic acid, etc.) is the Marassé modification - carboxylation of a mixture of phenol and potassium carbonate with carbon dioxide at 170 ° C and a pressure of 9-13 MPa.
Electrolysis of aqueous solutions of carboxylic acid salts (anodic synthesis) leads to the formation of alkanes:
The first stage of the process is the anodic oxidation of acid anions to radicals:
Hydrogen and hydroxide of the corresponding metal are formed at the cathode. The Kolbe reaction is applicable to obtain both unbranched and branched alkanes.
Exercise 2. Write down the reaction equations for the production by the Kolbe method: (a) 2,5-dimethylhexane and (b) 3,4-dimethylhexane.
Recovery of alkyl halides
A convenient way to obtain alkanes is the reduction of alkyl halides with zinc in aqueous solutions of acids:
Common reagents such as lithium aluminum hydride, sodium borohydride, sodium or lithium in tert- butyl alcohol , and catalytic reduction with hydrogen. Alkyl iodides can also be reduced by heating with hydroiodic acid.
Decarboxylation of carboxylic acids (Dumas)
When carboxylic acids are heated with alkalis, alkanes are formed with the number of carbon atoms one less than that of the original acid:
This reaction can be used to obtain only lower alkanes, since in the case of using higher carboxylic acids, a large number of by-products are formed.
Alkane reactions
Compared to other classes of organic compounds, alkanes are little reactive. The chemical inertness of alkanes explains their name “paraffins”. The reason for the chemical stability of alkanes is the high strength of the non-polar σ-bonds C-C and C-H. In addition, the C – C and C – H bonds are characterized by very low polarizability.
Because of this, bonds in alkanes do not exhibit a tendency to heterolytic rupture. Alkanes are not affected by concentrated acids and alkalis and they are not oxidized even by strong oxidants. At the same time, nonpolar bonds of alkanes are capable of homolytic decomposition.
Despite the fact that the C-C bond is less strong than the C-H bond (the C-C bond energy is about 88 kcal / mol, and the C-H bond is 98 kcal / mol), the latter breaks more easily, since it is on the surface of the molecule and is more accessible for attack by the reagent.
Chemical transformations of alkanes usually take place as a result of homolytic cleavage of the C - H bond, followed by the replacement of hydrogen atoms with other atoms. Thus, substitution reactions are characteristic of alkanes.
Halogenation
Methane, ethane and other alkanes react with fluorine, chlorine and bromine, but hardly react with iodine. The reaction between an alkane and a halogen is called halogenation.
A. Chlorination of methane
Chlorination of methane is of practical importance. The reaction is carried out under the influence of illumination or by heating to 300 ° C.
Let us consider the mechanism of this reaction using the example of the formation of methyl chloride. The mechanism means a detailed description of the process of converting reagents into products. It was found that the chlorination of methane proceeds according to the radical chain mechanism S R.
When exposed to light or heat, the chlorine molecule breaks down into two chlorine atoms - two free radicals.
The chlorine radical, interacting with a methane molecule, removes a hydrogen atom from the latter to form an HCl molecule and a free methyl radical:
CH 4 + Cl. ® CH 3. + HCl chain extension
CH 3. + Cl-Cl® CH 3 -Cl + Cl. chain continuation
The chlorine atom will further react with a methane molecule, etc. Theoretically, a single chlorine atom can cause chlorination of an infinite number of methane molecules, and therefore the process is called a chain process. Chains can be broken when radicals interact with each other:
CH 3. + Cl. ® CH 3 -Cl
CH 3. + CH 3. ® CH 3 -CH 3 Open circuit
Cl. + Cl. ® Cl-Cl
or with the vessel wall
Formally, a free methyl radical has a tetrahedral structure:
However, due to the small value inversion barrier(transition of one form of a molecule to another), its statistically most probable state is flat.
As a result of the methane chlorination reaction, a mixture of all four possible products of the replacement of hydrogen atoms with chlorine atoms is formed:
The ratio between the various chlorination products depends on the ratio of methane to chlorine. If it is necessary to obtain methyl chloride, an excess of methane should be taken, and an excess of carbon tetrachloride - chlorine.
FLASK REACTION
reaction, method of obtaining hydrocarbons by electrolysis of solutions of salts of carboxylic acids (electrochemical synthesis):
During electrolysis, mixtures of salts of various acids are formed, along with symmetric (RR, R "-R"), also asymmetric hydrocarbons (RR "). K. R. allows to obtain higher monocarboxylic (1) and dicarboxylic (2) acids (after hydrolysis of the corresponding esters ):
RCOO- + R "OOC (CH2) n COO-R (CH2) n COOR" (1)
2ROOC (CH2) nCOO-ROOC (CH2) nCOOR (2)
K. p. finds application in industry, for example, for the production of sebacic acid, which is used in the production of polyamides and fragrances. The reaction was proposed by the German chemist A. V. G. Kolbe in 1849.
Lit .: Serrey A., Handbook of organic reactions, trans. from English., M., 1962; Advances in organic chemistry, v. 1, N. Y., 1960, p. 1-34.
Great Soviet Encyclopedia, TSB. 2012
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(slang.) - here: a rapid fall in prices after the previous ... - REACTION in Medical terms:
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(Kolbe) Adolf Wilhelm Hermann (1818-84) German chemist. Developed methods for the synthesis of acetic (1845), salicylic (1860, Kolbe-Schmitt reaction) and formic ... - REACTION
Reaction (polit.) - in a broad sense, means a social movement in a direction sharply opposite to the previous or modern, if it is caused by its extremes. So … - REACTION in the Modern Encyclopedic Dictionary:
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[latin re. against + actio action] 1) action arising in response to a particular action; 2) in biology, the answer is ... - REACTION in the Encyclopedic Dictionary:
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1, -i, g. I. see react. 2. The transformation of some substances into others (chemical reaction) or the transformation of atomic nuclei due to their ... - REACTION
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ЌOLBE Georg (1877-1947), it. sculptor. Harmonious, plastically clear statues of young men and women ("The Dancer", 1911-12), ... - FLASK in the Big Russian Encyclopedic Dictionary:
ЌOLBE (Kolbe) Adolf Wilhelm Hermann (1818-84), it. chemist. He developed methods for the synthesis of acetic (1845), salicylic (1860, K.-Schmitt reaction) and formic ... - REACTION in the Complete Accentuated Paradigm by Zaliznyak:
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(Kolbe) Adolf Wilhelm Hermann (1818-84), German chemist. He developed methods for the synthesis of acetic (1845), salicylic (1860, the Kolbe-Schmitt reaction) and ... - REACTION in the Explanatory Dictionary of the Russian Language by Ushakov:
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I w. 1. Action, deed arising in response to a particular impact. 2. The body's response to this or that ... - KOLBE, MAXIMILIAN in the Encyclopedia of the Third Reich:
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(Kolbe) Adolf Wilhelm Hermann (27.9.1818, Ellhausen, - 25.11.1884, Leipzig), German chemist. Since 1851 professor at Marburg, and since 1865 at Leipzig universities. ... - COLLET - SCHMITT'S REACTION in the Great Soviet Encyclopedia, TSB:
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Acetic acid (chem.); its structure. - The structure of U. acid has interested chemists since the discovery of trichloroacetic acid by Dumas, since this discovery was ...
Carboxylation of phenolates according to the Kolbe - Schmidt reaction makes it possible to obtain ortho-hydroxyaromatic carboxylic acids from sodium phenolates. The Kolbe - Schmidt reaction occurs with the participation of carbon dioxide $ CO_2 $:
Picture 1.
Features of the Kolbe - Schmidt reaction
An original technique for introducing carboxyl groups into the aromatic system was discovered by G. Kolbe in 1860. When dry alkaline phenolate is heated with carbon dioxide at temperatures above 150 $ ^ \ circ $ C and a pressure of about 5 atm, an alkaline salt of salicylic acid is formed:
Figure 2.
With the participation of phenolates of potassium, rubidium and cesium, a similar reaction proceeds with the formation of predominantly para-substituted hydroxyaromatic acids.
Figure 3.
It is not phenols that are introduced into the reaction, but phenolates that are active for electrophilic substitution, because carbon dioxide is a very weak electrophile. This is explained by the formation of an intermediate complex of sodium phenolate and carbon dioxide, in which the sodium atom is coordinated with two oxygen atoms, one of which is included in the $ CO_2 $ molecule. Due to a certain polarization, the carbon atom acquires a greater positive charge and a convenient location for attacking the opto-position of the phenolic ring.
Figure 4.
Application of the Kolbe - Schmidt reaction
Rearrangement of monosalicylates and alkaline salts of 2-naphthol
Anhydrous potassium and rubidium monosalicylates when heated above 200-220 $ ^ \ circ $ С give dipotassium and dirubidium salts pair-hydroxybenzoic acid and phenol.
Figure 7.
Alkaline salts of potassium and cesium of 2-hydroxybenzoic (salicylic) acid are rearranged to form di-alkali salts 4 -hydroxybenzoic acid:
Figure 8.
Alkali salts of sodium and lithium pair-hydroxybenzoic acid, on the contrary, when heated, are rearranged into the di-alkali salt of salicylic acid:
Figure 9.
It follows from this that the carboxylation of alkali phenolates is a reversible reaction and their direction depends only on the nature of the cation. Similar patterns are observed during the corboxylation of alkaline salts of 2-naphthol:
Figure 10.
Unlike monohydric phenols, diatomic and triatomic phenols are carboxylated under milder conditions. Thus, resorcinol is carboxylated when $ CO_2 $ is passed into an aqueous solution of its dipotassium salt at 50 $ ^ \ circ $ C with the formation of 2,4-dihydroxybenzoic acid.
Figure 11.
Reimer - Timan reaction
Phenols and some heterocyclic compounds such as pyrrole and indole can be formalized with chloroform under basic conditions (Reimer - Timan reaction). The entry of the aldehyde group is oriented to the ortho position, and only when they are both occupied, para-substituted derivatives are formed.
Figure 12.
It is known that chloroform in the presence of strong bases forms dichlorocarbene $: CCl_2 $, which is a real electrophilic particle.
Figure 13.
This is confirmed by the formation of ring expansion products characteristic of the action of $: CCl_2 $, namely, pyridine in the reaction with pyrrole, and the release of the products of addition of dichlorocarbene to aromatic rings in the ipso position, as this is observed in the formylation reaction of para-cresol. In the latter case, methyl groups cannot be cleaved, like a proton, under the action of an electrophile, and stabilization occurs through the migration of a proton to the dichloromethyl group.
Figure 14.
Organic synthesisMechanisms of chemical processes
Name reactions
Kolbe synthesisWurtz reaction
Kucherov's reaction
Lebedev's reaction
Konovalov's reaction
Zaitsev's rule
Markovnikov's rule
Wöhler reaction
Dumas reaction
Wagner reaction
Berthelot reaction
Diels - Alder reaction
Zelinsky - Kazansky reaction
Wöhler reaction
Friedrich Wöhler,1800 - 1882
Oxalic acid synthesis
in the hydrolysis of cyanogen in
acidic environment, 1824
Synthesis of urea from
carbon dioxide and ammonia
at high temperatures and
pressure, 1828
Acetylene production at
hydrolysis of calcium carbide
(obtained by fusion
coke and lime), 1829
Wöhler reactions
Hydrolysis of cyanogen to form oxalic acidacid, 1824
Wöhler reactions
Synthesis of urea from carbon dioxide and ammonia,1828 g.
“I can’t be silent any longer,” Wöhler writes to his
teacher, J. Ya. Berzelius, - and must inform
To you that I can get urea without the help of the kidneys
dogs, humans and generally without the participation of any
living creature ... "
T0
CO2 + 2NH3 → H2O +
Wöhler reactions
Obtaining acetylene by hydrolysis of carbidecalcium, 1862
In 1892 Moissan (France) and Wilson (Canada)
proposed the design of an electric arc furnace,
suitable for industrial use:
obtaining calcium carbide by fusion
burnt lime and coal
Or CaCO3 → CaO + CO2; CaO + 3C → CaC2 + CO
Dumas reaction
Fusion of carboxylic acid saltswith alkalis:
0
CaO, T
Н3С-СООNa + NaOH → CH4 + Na2CO3
Decarboxylation of carboxylic acid salts (- CO2)
French chemist.
Member of the French Academy of Sciences
(1832)
Member of the Paris Academy
medicine (1843)
President of the Academy of Sciences (1843)
He was also involved in state
activities. In 1850-1851 the Minister of Agriculture and
trade in government
Jean Baptiste André Dumas,
Napoleon Bonoparte.
1800 - 1884
Wagner reaction
Mild oxidation of alkenesaqueous solution
potassium permanganate with
formation of a diatomic
alcohol
Egor Egorovich Wagner,
1849 - 1903
Konovalov's reaction
Mikhail IvanovichKonovalov,
1858 - 1906
Nitration of hydrocarbons
diluted НNО3 at
elevated or
normal pressure (by
free radical
mechanism).
Doctoral dissertation
"Nitrating action
weak nitrous acid on
saturated hydrocarbons
character "(1893)
10. Berthelot's reaction
Ethanol synthesis by ethylene hydration:French chemist.
Member of the Paris Academy of Sciences
(1873)
Corresponding member
Petersburg Academy of Sciences (since
1876)
In 1895-1896. Berthelot was
foreign minister
France.
Marcelin Berthelot,
1827 - 1907
11. Rules of A.M. Zaitsev (1875), V.V. Markovnikov (1869)
AlexanderMikhailovich Zaitsev,
1841-1910
Vladimir Vasilievich
Markovnikov,
1837-1904
12. Rules of A.M. Zaitsev (1875), V.V. Markovnikov (1869)
When protic acids or water are attached toasymmetric unsaturated hydrocarbons
the hydrogen proton joins the most
hydrogenated carbon atom
(product formation proceeds through the most
stable carbocation) - the rule
Markovnikov. Repeat. excl. from the rule.
When split off, a hydrogen proton is split off
from the least hydrogenated atom
carbon - Zaitsev's rule.
13. Exercises according to the rules of Zaitsev and Markovnikov
From which halogenated hydrocarbonsunder the action of an alcohol solution
potassium hydroxide can be obtained:
1) 2-methylpentene-1
2) 3-methylpentene-2
3) 4-methyl-3-ethylpentene-2
4) 3-ethylhexene-2?
14. Würz reaction, 1865
Synthesis of symmetric alkanesfrom alkyl halides to
reactions with sodium (even easier
with potassium)
Charles Adolph Würz,
1817- 1884
President of the Paris
academies of sciences
15. Kolbe synthesis, 1849
Electrolysis of aqueous solutionspotassium and sodium salts
carboxylic acids.
Adolf Wilhelm
Herman Kolbe,
1818-1884, Germany
16. Grignard's reagent, 1912
Organomagnesium chemicalconnections like
magnesium methyl iodide CH3MgI
magnesium benzene bromide C6H5MgBr.
Victor Grignard,
1871-1935, France
Nobel laureate
chemistry awards
17. Diels - Alder reaction
Diene synthesis - reaction, cycloadditiondienophiles and conjugated dienes to form
six-membered cycle:
18. Diels - Alder reaction
Kurt Albert, Germany1902 - 1958
Otto Paul Hermann Diels,
Germany, 1876 - 1954
In 1950 they were awarded for diene synthesis
Nobel Prize in Chemistry
19. Reaction of Zelinsky - Kazansky
ɳ = 70%20. Reaction of Zelinsky - Kazansky
Graduated from NovorossiyskUniversity in Odessa (1884)
Professor of Moscow
university (1911-1917)
Organized the institute
organic chemistry of the USSR Academy of Sciences
(1935), since 1953 the institute has worn it
name
Created the first coal
gas mask (1915) taken on
Nikolay Dmitrievich
armament during the First
Zelinsky,
world war in Russian and
Russian empire,
allied armies.
1861 - 1953
21. Coal gas masks
Soldiers of the Czech Legion of the Russian Army ingas masks Zelinsky-Kummant
22. Reaction of Zelinsky - Kazansky
Boris AlexandrovichKazansky,
1891 - 1973
Graduated from Moscow University
(1919)
Worked in Moscow
university led
N. D. Zelinsky
Taught at Moscow
university workshop on
general chemistry, quality and
quantitative analysis, and
later in organic chemistry,
petroleum chemistry, organic
catalysis
Academician of the USSR Academy of Sciences
23. Kucherov's reaction
Hydration of alkynes inpresence of Hg2 + salts in
acidic environment.
Mikhail Grigorievich
Kucherov,
1850 - 1911
24. Lebedev's reaction
Lebedev proposed a one-step methodobtaining butadiene from ethyl alcohol
(catalysts: ZnO, Al2O3; T 400-5000С)
2CH3CH2OH
Sergey
Vasilevich
Lebedev,
1874-1934.
2H2O + CH2 = CH-CH = CH2 + H2
Thanks to the works of Lebedev
industrial production
synthetic rubber started in the Soviet
Union in 1932 - for the first time in the world.
25. Reagents
Grignard's reagentTollens' reagent OH
Ammonia solution of copper chloride (I)
[Cu (NH3) 2] Cl
26. Catalysts
Na catalyst in liquid ammoniaLindlar catalyst
Na to NH3
Pd // Pb2 +
An acidic solution of copper (I) chloride in ammonium chloride
NH4Cl, CuCl
Ziegler - Natta
See which reactions are used for (workbook)
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