Chemistry - STRUCTURAL ISOMERISM Question with Solution | TestHub

The compound is 1-methylcyclohex-2-en-1-ol - an allylic alcohol, not an enol : the $\mathrm{OH}$ sits on an sp3 carbon and there is no $\mathrm{C}=\mathrm{O}$ or C=C-OH unit that could tautomerise. The only exchangeable hydrogen is the O-H proton itself, which swaps instantly with ${\mathrm{D}}_2\mathrm{O}$. Hence only 1 hydrogen is replaced.