2-Methylbutan-2-ol is heated with conc. $\mathrm{H}{}_2\mathrm{SO}{}_4$ at 440 K. The major alkene formed is

Protonation and loss of water give the tertiary cation $(\mathrm{CH}{}_3){}_2\mathrm{C}{}^{+}\mathrm{CH}{}_2\mathrm{CH}{}_3$. Loss of a beta-hydrogen follows Saytzeff's rule and gives the more substituted (trisubstituted) alkene, 2-methylbut-2-ene.