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

Ionisation gives the secondary cation $\mathrm{CH}{}_3-\mathrm{CH}{}^{+}-\mathrm{C}(\mathrm{CH}{}_3){}_3$. A 1,2-methyl shift gives the tertiary cation $(\mathrm{CH}{}_3){}_2\mathrm{CH}-\mathrm{C}{}^{+}(\mathrm{CH}{}_3){}_2$. Loss of the proton from the isopropyl CH gives the tetrasubstituted alkene 2,3-dimethylbut-2-ene (Saytzeff), the major product.