Q22-62E - Organic Chemistry (Mcmurry)

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.

Step-by-Step Solution

Answer

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

Step 1: Acid-catalyzed enol formation

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

 

                                             Acid catalysed enolisation

Step 2: 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