# Does presence of alkyl groups on alpha carbon increase yield of alkane in Kolbe's Decarboxylation?

We know that, during the synthesis of alkanes by Kolbe's Decarboxylation reaction, the reaction proceeds via a free radical $\ce{R.}$ at the anode.

So, an alkyl group, say methyl, when substituted at the alpha carbon will increase the yield of alkane since the radical is stabilized by hyperconjugation. But my book states that the presence of alkyl group on alpha carbon decreases the yield of alkane. Why is it so?

• The yield of alkane is not the same as stability of the radical. Self-coupling of these substituted radicals (tertiary?) can yield to disproportionation to an alkane and alkene. E.g.; t-butyl radical to isobutane and isobutylene. – user55119 May 10 '18 at 14:32

I have done some electrosynthesis work using the Kolbe reaction, what I found was with straight chain carboxylic acids that my platinum anode was quickly fouled.

When I had some branching at the beta site, I had much less electrode fouling and I got a good yield of my alkane.

• Beta site? Did you do any work with substitution at the alpha site as the question states? – user138523 May 10 '18 at 18:48
• Sadly no I only worked with things with beta alkyls – Nuclear Chemist May 10 '18 at 20:09