JEE Main · 2026 · 22 Jan 2026 · Shift 2 · Alcohols Phenols and Ethers

The target $(\mathrm{C}{\mathrm{H}}_3{)}_3\mathrm{C}-\mathrm{CH}(\mathrm{OH})-\mathrm{C}{\mathrm{H}}_3$ is a secondary alcohol that retains an intact $tert$-butyl group. Addition of methylmagnesium bromide to pivaldehyde gives it directly, reductive ozonolysis of the symmetrical tetrasubstituted alkene followed by $\mathrm{NaB}{\mathrm{H}}_4$ delivers it through pinacolone, and lithium aluminium hydride reduction of pinacolone also furnishes it, so these three routes succeed. Acid-catalysed hydration of $3,3$-dimethylbut-$1$-ene proceeds through a secondary carbocation that rearranges by a $1,2$-methyl shift to the more stable tertiary ion, giving $2,3$-dimethylbutan-$2$-ol instead of the target. Mercuric-ion hydration of $3,3$-dimethylbut-$1$-yne stops at the methyl ketone pinacolone and does not give an alcohol at all. The alcohol cannot be prepared by routes B and E only.