Question

Which of the following has unstable enol form?

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

Enol form of (a) is phenol which is an aromatic ring and highly stable.
Enol form of (b) is also highly stable because it is aromatic

Enol form of (c) is non-aromatic.

Enol form of (d) :


Here the enol form is highly unstable because it is an anti-aromatic in nature. Hence, keto form of (d) is stable and more dominant.