Decarboxylation (soda lime)
The sodium salt of a carboxylic acid heated with soda lime (NaOH and CaO) loses CO2 to give an alkane with one carbon fewer.
Sodium ethanoateCH₃COONaCompound - Step 1
NaOH + CaO (soda lime), heat
MethaneCH₄Alkane
How it works
- Soda lime supplies the base.
- The carboxylate loses CO₂ to a carbanion.
- Protonation gives the alkane and sodium carbonate remains.
What it makes
Methane from sodium ethanoate, benzene from sodium benzoate.
Where it fails
The product has one carbon less. Do not confuse it with Kolbe electrolysis, which joins two alkyl groups.
Class 11, Chapter 9 Hydrocarbons
Decarboxylation (soda lime): quick answers
What is soda lime?
A mixture of NaOH and CaO.
How many carbons does the alkane have?
One fewer than the acid.
How is benzene made this way?
Heat sodium benzoate with soda lime.