3-Methylbut-1-ene is hydrated with dilute $\mathrm{H}{}_2\mathrm{SO}{}_4$ (acid-catalysed hydration). The major alcohol is

Protonation gives the secondary cation at C-2, which undergoes a 1,2-hydride shift from C-3 to give the more stable tertiary cation. Water capture at C-3 (the carbon bearing the methyls) gives $(\mathrm{CH}{}_3){}_2\mathrm{C}(\mathrm{OH})-\mathrm{CH}{}_2\mathrm{CH}{}_3$, 2-methylbutan-2-ol.