Kolbeelektrolyysi

Kolbeelektrolyysi, also known as the Kolbe reaction or Kolbe electrolysis, is an organic chemical reaction where the carboxylate anion of a carboxylic acid is decarboxylated and oxidized to form a radical. This radical then couples with another radical of the same type to form a new alkane or alkene, depending on the starting material. The reaction is carried out by electrolyzing a solution of the sodium or potassium salt of a carboxylic acid in an inert solvent, typically methanol or ethanol.

The process involves the electrochemical oxidation of the carboxylate anion at the anode. First, the carboxylate anion loses an electron to form a carboxyl radical. This carboxyl radical then rapidly loses a carbon dioxide molecule, yielding an alkyl radical. Two of these alkyl radicals then combine to form a symmetrical alkane. For example, electrolysis of sodium acetate yields ethane. If an unsaturated carboxylic acid is used, alkenes can be formed.

The Kolbe electrolysis has been a useful method for synthesizing symmetrical alkanes and alkenes. However, it has limitations, including the formation of byproducts from side reactions and the difficulty in controlling the coupling process when different carboxylic acids are mixed. Modern organic synthesis often employs other methods for alkane and alkene formation due to these limitations. The reaction is named after the German chemist Hermann Kolbe, who discovered it in 1849.