Which of the following shows keto-enol isomer | vedclass

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(B) For a compound to exhibit keto-enol isomerism,it must possess at least one $\alpha$-hydrogen atom adjacent to the carbonyl group $(C=O)$.$1$. Opti

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(B) For a compound to exhibit keto-enol isomerism,it must possess at least one $\alpha$-hydrogen atom adjacent to the carbonyl group $(C=O)$.$1$. Option $A$ ($4$,$4$-dimethylcyclohexa$-2,5-$dien$-1-$one): The carbon adjacent to the carbonyl group is quaternary (bonded to two methyl groups),so it has no $\alpha$-hydrogen.$2$. Option $B$ (cyclohexa$-2,5-$dien$-1-$one): The carbons adjacent to the carbonyl group are $CH$ groups,which possess $\alpha$-hydrogen atoms. These hydrogens are acidic and can participate in keto-enol tautomerism.$3$. Option $C$ ($2$,$2$-dichlorocyclohex$-2-$en$-1-$one): The $\alpha$-carbon is bonded to two chlorine atoms,so it has no $\alpha$-hydrogen.$4$. Option $D$ (spiro[$5.5$]undeca$-1,4-$dien$-3-$one): The $\alpha$-carbon is a quaternary spiro carbon,so it has no $\alpha$-hydrogen.Therefore,only the compound in option $B$ shows keto-enol isomerism.

Which of the following shows keto-enol isomerism?

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