The dehydration of alcohols involves passing alcohol vapours over heated alumina (Al₂O₃). The reaction is highly temperature-dependent, which determines the major product formed:

1. At Higher Temperatures (approx. 633 K): Intramolecular dehydration (elimination) dominates, leading to the formation of Alkenes .
2. At Lower Temperatures (approx. 513–523 K): Intermolecular dehydration (substitution) dominates, leading to the formation of Ethers. Therefore, temperature is the effective factor that controls the selectivity of the reaction toward alkenes.