Question

Which of the following pairs are keto–enol tautomers?

Short answer

Only c and e are keto-enol tautomerism

Step-by-step solution

Definition of keto-enol tautomerism-

keto–enol is a chemical equilibrium between a keto form (a ketone or an aldehyde) and an enol is referred to as tautomerism (an alcohol). The keto and enol forms are referred to as tautomers. Because the interconversion of the two forms requires the movement of an alpha hydrogen atom as well as the reorganisation of bonding electrons, the isomerism qualifies as tautomerism.

Only c and e are keto-enol tautomerism

and

Displays keto-enol tautomerisation. An OH group is bonded to a sp² carbon in an enol tautomer. The structures in d are not enol tautomers because the oxygen is not on the same carbon.