I came across this question:

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I propose two things to happen:

  1. It can undergo Aldol condensation


  1. it can undergo SN by replacing $\ce{-Cl}$ with $\ce{-OH}$.

But apparently, both these mechanism give the wrong product. I’m unable to find out what is going on.


1 Answer 1


I see what went wrong. Such questions are often confused with aldol or cannizarro as they have a carbonyl group and a base is given.

Actually this is a completely different name reaction called Favorskii rearrangement. The key to identify it is that its applicable to α-halo ketones.

In Favorskii rearrangement, the base takes α-hydrogen from that side of ketone which is opposite to the side having the halogen. It then forms a 3 member cyclic ring as an intermediate product. The product formed is a carboxylic acid derivative, mostly ester.

You can learn more at organic-chemistry.org or wikipedia


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