4-methylcyclohexanol → 4-methylcyclohexene + H₂O
Conditions:
* Acid catalyst: Typically, a strong acid like phosphoric acid (H₃PO₄) or sulfuric acid (H₂SO₄) is used.
* Heat: The reaction is usually carried out at elevated temperatures, around 150-180°C.
Mechanism:
1. Protonation: The alcohol group in 4-methylcyclohexanol is protonated by the acid catalyst, forming a good leaving group (water).
2. Carbocation Formation: The loss of water results in the formation of a carbocation intermediate.
3. Dehydration: A proton is removed from a carbon adjacent to the carbocation, leading to the formation of the double bond in 4-methylcyclohexene.
Note:
* The reaction can also proceed through a concerted mechanism, where the protonation and loss of water occur simultaneously.
* Other dehydrating agents, like phosphorus pentoxide (P₂O₅), can also be used.
* The reaction can produce side products, such as other isomers of 4-methylcyclohexene.
