__NOTOC__ The Kolbe electrolysis or Kolbe reaction is an

organic reaction Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, mechanistic organ ...

named after

Hermann Kolbe Adolph Wilhelm Hermann Kolbe (27 September 1818 – 25 November 1884) was a German chemist and academic, and a major contributor to the birth of modern organic chemistry. He was a professor at Marburg and Leipzig. Kolbe was the first to apply t ...

. The Kolbe reaction is formally a decarboxylative dimerisation of two

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...

s (or

carboxylate ion In organic chemistry, a carboxylate is the conjugate base of a carboxylic acid, (or ). It is an Ion#anion , anion, an ion with negative charge. Carboxylate salts are salt (chemistry), salts that have the general formula , where M is a metal ...

s). The overall reaction is: : If a mixture of two different carboxylates are used, all combinations of them are generally seen as the organic product structures: : 3 R₁COO⁻ + 3 R₂COO⁻ → R₁−R₁ + R₁−R₂ + R₂−R₂ + 6 CO₂ + 6 e⁻ The

reaction mechanism In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical reaction occurs. A chemical mechanism is a theoretical conjecture that tries to describe in detail what takes place at each stage ...

involves a two-stage radical process:

electrochemical Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference and identifiable chemical change. These reactions involve electrons moving via an electronically conducting phase (typi ...

decarboxylation gives a radical intermediate, which combine to form a covalent bond. As an example, electrolysis of

acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main compone ...

yields

ethane Ethane ( , ) is a naturally occurring Organic compound, organic chemical compound with chemical formula . At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is List of purification methods ...

and

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

: :CH₃COOH → CH₃COO⁻ → CH₃COO· → CH₃· + CO₂ :2CH₃· → CH₃CH₃ Another example is the synthesis of 2,7-dimethyl-2,7-dinitrooctane from 4-methyl-4-nitrovaleric acid: : The Kolbe reaction has also been occasionally used in

cross-coupling reaction In organic chemistry, a cross-coupling reaction is a reaction where two different fragments are joined. Cross-couplings are a subset of the more general coupling reactions. Often cross-coupling reactions require metal catalysts. One important re ...

s. In 2022, it was discovered that the Kolbe electrolysis is enhanced if an alternating square wave current is used instead of a

direct current Direct current (DC) is one-directional electric current, flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor (material), conductor such as a wire, but can also flow throug ...

Applications

Kolbe electrolysis has a few industrial applications. In one example, sebacic acid has been produced commercially by Kolbe electrolysis of

adipic acid Adipic acid or hexanedioic acid is the organic compound with the formula C6H10O4. It a white crystalline powder at standard temperature and pressure. From an industrial perspective, it is the most important dicarboxylic acid at about 2.5 billion ...

. Kolbe electrolysis has been examined for converting biomass into

biodiesel Biodiesel is a renewable biofuel, a form of diesel fuel, derived from biological sources like vegetable oils, animal fats, or recycled greases, and consisting of long-chain fatty acid esters. It is typically made from fats. The roots of bi ...

and for

grafting Grafting or graftage is a horticulture, horticultural technique whereby tissues of plants are joined so as to continue their growth together. The upper part of the combined plant is called the scion () while the lower part is called the roots ...

of carbon electrodes.

References

External links

* {{electrolysis Organic redox reactions Electrolysis Name reactions

Applications

See also

References

Further reading

External links