Question

Among the given ketones, the compound which does not enolize is:

• A. $I$ only
• B. $II$ only
• C. $III$ only
• D. All can enolize

Answer 1

The correct option is B $II$ only

Enol form of $I$ and $III$:



In $I$, double bond will not be formed at bridge head because it will violate Bredt's rule.
Enol form of $III$ is highly stable because it forms an aromatic ring.

Enol form of $II$: Here there is alpha hydrogen at bridge head only.



This enol form is highly unstable because it violates Bredt's rule(double bond at bridge head is strained and very unstable).
So, the ketone $II$ does not enolize.