Q31E - Organic Chemistry (Mcmurry)

Question

The Favorskii reaction involves the treatment of an -bromo ketone with a base to yield a ring-contracted product. For example, the reaction of 2-bromocyclohexanone with aqueous NaOH yields cyclopentanecarboxylic acid. Propose a mechanism.

Step-by-Step Solution

Answer

Step 1: Favorskii reaction

The Favorskii reaction involves the treatment of an α-halo bromo ketone with the base to produce a ring-contracted product.

Step 2: Mechanism

The mechanism for the given reaction involves the following steps:

In the second step, a carbanion attacks the carbocation formed by the release of bromine shown in the third step and forms the respective product.

                               Mechanism of the reaction