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Oxidative Decarboxylation

Oxidative Decarboxylation of Carboxylic Acids: Kolbe Electrolysis

In 1849 during the electrolysis of potassium acetate, Hermann Kolbe (Professor of Chemistry in Marburg and Leipzig) discovered the reaction that carries his name . He could demonstrate the existence of carbon dioxide and ethane at the anode.

In contrast to the Hunsdiecker reaction, oxidation does not take place chemically but electrolytically. Alkanes are formed by dimerisation of the generated radicals.

Fig.1

The Kolbe electrolysis is an example of an organic redox reaction that takes place in an electrochemical cell. The methodology has several advantages, for example the possibility to control the potential of the electrode and the simplicity of the reaction because no reducing or oxidizing agents are required.

The Kolbe synthesis, not to be confused with the Kolbe electrolysis, is used for the synthesis of long-chain diesters:

Fig.2

Furthermore, electrochemical processes are well suited for the reduction of alkyl halides to alkanes, of carbonyl compounds to alcohols, and of nitro compounds to amines. Electrochemical oxidations are used for the conversion of alcohols into ketones, of amines into imines, and of sulfides into sulfoxides and sulfones.

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