Kolbe electrolysis template

At the anode acetate gives up one electron; the acetoxyl radical loses CO₂ and two methyl radicals combine to ethane. Water is reduced to H₂ and OH⁻ at the cathode.

Mechanism step by step

Electrolysis of a carboxylate salt: radicals lose CO₂ and pair up to an alkane

1. Anode: oxidation – Acetate gives one electron to the anode: an acetoxyl radical
2. Decarboxylation – The acetoxyl radical loses CO₂: a methyl radical
3. Coupling – Two methyl radicals pair their electrons: ethane

Key points

• Overall: 2 CH₃COONa + 2 H₂O → C₂H₆ + 2 CO₂ + H₂ + 2 NaOH.
• Cathode: 2 H₂O + 2 e⁻ → H₂ + 2 OH⁻, so the solution turns alkaline.
• Gives alkanes with an even number of carbons (R–R); a mixture of two salts gives three alkanes.
• Methane cannot be made this way: the smallest product is ethane.

Drawn with 30 atoms, 9 arrows, 9 shapes – every one editable in MolDraw.

Sources

• Smith, March's Advanced Organic Chemistry, 8th ed., Wiley 2020 Textbook