Acid-Catalyzed Elimination Reactions

Alcohols and ethers rarely undergo substitution or elimination unless strong acid is present.  Thus the dehydration of alcohols to alkenes is an acid-catalyzed reaction requiring strong acids such as sulfuric or phosphoric acid:

These are synthetically useful reactions for the preparation of alkenes when the alkene is less available than the alcohol. They can occur by either the E1 or E2 mechanism depending on the alcohol, the acid catalyst, the solvent, and the temperature.