Question

Ketones react slowly with benzene selenenyl chloride in the presence of HCl to yield a-phenyl seleno ketones. Propose a mechanism for this acid-catalyzed a-substitution reaction.

Short answer

The reaction mechanism starts with keto-enol tautomerism and ends with the loss of a proton.

Step-by-step solution

Acid-catalyzed enol formation

The alpha hydrogen of the ketone participates in enolisation in the presence of acid HCl.

Acid catalysed enolisation

Explanation

The attack at enol π electrons on benzene selenenyl chloride with loss of

Cl^-ith the loss of proton by the attack of Base in the solution.

The final product