2-Methylcyclohexan-1-ol is heated with conc. $\mathrm{H}{}_3\mathrm{PO}{}_4$. The major alkene is

Protonation and loss of water give the secondary cation at C-1. Loss of the tertiary C-2 hydrogen gives the trisubstituted ring alkene 1-methylcyclohexene (Saytzeff), more stable than 3-methylcyclohexene (disubstituted) or methylenecyclohexane.