Question

Which of the following will show tautomerism?

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

Carbonyl compound in which delocalisation takes place between a >C=O group and an alpha H where the equilibrium lies between a keto form and an enol form is called Keto-enol tautomerism.
In compound (c), there is no $\alpha -Hydrogen$ so it does not shows tautomerism.
In compounds (b) and (d), $\alpha -Hydrogen$ is attached to $s{p}^2$ hybridised carbon so it won't involve in delocalisation with >C=O group. Hence, it does not exhibit tautomerism.
Only compound (a) shows Keto-enol tautomerism due to the presence of $\alpha -Hydrogen$