Q28E - Organic Chemistry (Mcmurry)

Question

2-Bromo-6, 6-dimethylcyclohexanone gives 2, 2-dimethylcyclopentane-carboxylic acid on treatment with aqueous NaOH followed by acidification, a process called the Favorskii reaction. Propose a mechanism.

Step-by-Step Solution

Answer

dimethylcyclohexanone gives 2, 2-dimethylcyclopentane-carboxylic acid on treatment with A mechanism for the Favorski rearrangement, in which 2-bromo-6, 6-aqueous NaOH is shown below

Step 1: Definition of mechanism

The sequence of elementary steps by which a chemical reaction occurs is defined as mechanism

Step 2: Mechanism for the Favorski rearrangement

The nucleophilic attack of the hydroxide ion on the carbonyl carbon in 2 bromo-6, 6-dimethylcyclohexanone yields an oxyanion. The flow of electrons from the negatively charged oxygen followed by breaking of the${\mathbf{C}}_{\mathbf{1}}\mathbf{-}{\mathbf{C}}_{\mathbf{6}}$bond and the formation of${\mathbf{C}}_{\mathbf{6}}\mathbf{-}{\mathbf{C}}_{\mathbf{2}}$bond eliminates a bromide ion to yield cyclopentane carboxylic acid.

A mechanism for the Favorski rearrangement, in which 2-bromo-6, 6-dimethylcyclohexanone gives 2, 2-dimethylcyclopentane-carboxylic acid and bromide ion on treatment with aqueous NaOH