Kolbe electrolysis

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The Kolbe electrolysis or Kolbe reaction is an organic reaction named after Hermann Kolbe. [1] The Kolbe reaction is formally a decarboxylative dimerisation of two carboxylic acids (or carboxylate ions). The overall reaction is:

Contents

Electrolisis de Kolbe.png

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 involves a two-stage radical process: electrochemical decarboxylation gives a radical intermediate, which combine to form a covalent bond. [2] As an example, electrolysis of acetic acid yields ethane and carbon dioxide:

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: [3]

Kolbe electrolysis.svg

The Kolbe reaction has also been occationally used in cross-coupling reactions.

In 2022, it was discovered that the Kolbe electrolysis is enhanced if an alternating square wave current is used instead of a direct current. [4] [5]

Applications

Kolbe electrolysis has a few industrial applications. [6] In one example, sebacic acid has been produced commercially by Kolbe electrolysis of adipic acid. [7]

Kolbe electrolysis has been examined for converting biomass into biodiesel [8] [9] and for grafting of carbon electrodes. [10] [11]

See also

Related Research Articles

<span class="mw-page-title-main">Hermann Kolbe</span> German chemist (1818–1884)

Adolph Wilhelm Hermann Kolbe was a major contributor to the birth of modern organic chemistry. He was a professor at Marburg and Leipzig. Kolbe was the first to apply the term synthesis in a chemical context, and contributed to the philosophical demise of vitalism through synthesis of the organic substance acetic acid from carbon disulfide, and also contributed to the development of structural theory. This was done via modifications to the idea of "radicals" and accurate prediction of the existence of secondary and tertiary alcohols, and to the emerging array of organic reactions through his Kolbe electrolysis of carboxylate salts, the Kolbe-Schmitt reaction in the preparation of aspirin and the Kolbe nitrile synthesis. After studies with Wöhler and Bunsen, Kolbe was involved with the early internationalization of chemistry through work in London. He was elected to the Royal Swedish Academy of Sciences, and won the Royal Society of London's Davy Medal in the year of his death. Despite these accomplishments and his training important members of the next generation of chemists, Kolbe is best remembered for editing the Journal für Praktische Chemie for more than a decade, in which his vituperative essays on Kekulé's structure of benzene, van't Hoff's theory on the origin of chirality and Baeyer's reforms of nomenclature were personally critical and linguistically violent. Kolbe died of a heart attack in Leipzig at age 66, six years after the death of his wife, Charlotte. He was survived by four children.

In chemistry, chemical synthesis is the artificial execution of chemical reactions to obtain one or several products. This occurs by physical and chemical manipulations usually involving one or more reactions. In modern laboratory uses, the process is reproducible and reliable.

<span class="mw-page-title-main">Ethane</span> Organic compound (H3C–CH3)

Ethane is a naturally occurring organic chemical compound with chemical formula C
2
H
6
. At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is isolated on an industrial scale from natural gas and as a petrochemical by-product of petroleum refining. Its chief use is as feedstock for ethylene production.

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In organic chemistry, a nitrile is any organic compound that has a −C≡N functional group. The name of the compound is composed of a base, which includes the carbon of the −C≡N, suffixed with "nitrile", so for example CH3CH2C≡N is called "propionitrile". The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, including methyl cyanoacrylate, used in super glue, and nitrile rubber, a nitrile-containing polymer used in latex-free laboratory and medical gloves. Nitrile rubber is also widely used as automotive and other seals since it is resistant to fuels and oils. Organic compounds containing multiple nitrile groups are known as cyanocarbons.

<span class="mw-page-title-main">Sebacic acid</span> Chemical compound

Sebacic acid is a naturally occurring dicarboxylic acid with the chemical formula HO2C(CH2)8CO2H. It is a white flake or powdered solid. Sebaceus is Latin for tallow candle, sebum is Latin for tallow, and refers to its use in the manufacture of candles. Sebacic acid is a derivative of castor oil.

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The Kolbe–Schmitt reaction or Kolbe process is a carboxylation chemical reaction that proceeds by treating phenol with sodium hydroxide to form sodium phenoxide, then heating sodium phenoxide with carbon dioxide under pressure, then treating the product with sulfuric acid. The final product is an aromatic hydroxy acid which is also known as salicylic acid.

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Organic reductions or organic oxidations or organic redox reactions are redox reactions that take place with organic compounds. In organic chemistry oxidations and reductions are different from ordinary redox reactions, because many reactions carry the name but do not actually involve electron transfer. Instead the relevant criterion for organic oxidation is gain of oxygen and/or loss of hydrogen. Simple functional groups can be arranged in order of increasing oxidation state. The oxidation numbers are only an approximation:

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References

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  7. Seko, Maomi; Yomiyama, Akira; Isoya, Toshiro (1979). "Development of Kolbe Electrosynthesis of Sebacic Acid". CEER, Chemical Economy & Engineering Review. 11 (9): 48-50.
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