When 2-methylcyclohexanol is heated with concentrated hydrochloric acid, an E1 elimination reaction occurs. In this reaction, the hydroxyl group -OH in the alcohol is protonated by the hydrochloric acid to form a good leaving group water . Then, a carbocation is formed, and a neighboring hydrogen is removed by a base chloride ion, Cl- to form a double bond. The major product of this reaction is 1-methylcyclohexene. This is due to the Zaitsev's rule, which states that the more substituted alkene is the major product in an elimination reaction. In this case, 1-methylcyclohexene is more substituted than the alternative product, 3-methylcyclohexene, and therefore is the major product.