3-Methylbutan-2-ol is heated with conc. $\mathrm{H}{}_2\mathrm{SO}{}_4$. The major alkene is

Loss of water gives a secondary cation, which undergoes a 1,2-hydride shift to give the more stable tertiary cation $(\mathrm{CH}{}_3){}_2\mathrm{C}{}^{+}-\mathrm{CH}{}_2\mathrm{CH}{}_3$. Loss of a proton in the Saytzeff sense gives 2-methylbut-2-ene as the major product.