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

Protonation and loss of water give the secondary cation $(\mathrm{CH}{}_3){}_2\mathrm{CH}-\mathrm{CH}(+)-\mathrm{CH}{}_3$. A 1,2-hydride shift gives the tertiary cation $(\mathrm{CH}{}_3){}_2\mathrm{C}(+)-\mathrm{CH}{}_2-\mathrm{CH}{}_3$. Loss of a proton by the Saytzeff rule gives the most substituted alkene, 2-methylbut-2-ene.