Question

Keto-enol tautomerism is observed in :

• A.
• B.
• C.
• D.

Answer 1

The correct option is B

For a compound to exhibit keto-enol tautomerism, presence of $\alpha$-hydrogen is neccessary at its $s{p}^3$ hybridised ⍺-C atom. This is satisfied only by acetophenone. Hence it will exhibit keto-enol tautomerism.
Others benzaldehyde, benzophenone, option (d) do not have $\alpha$-hydrogen at their $s{p}^3$ hybridised ⍺-C atom thus they will not exhibit keto-enol tautomerism.