What Is Acid-Catalyzed Dehydration?

Acid-catalyzed dehydration is an important elimination reaction in organic chemistry, whereby water is removed from a compound, according to Old Dominion University. This chemical process is very important in converting alcohols into alkenes. During the process of acid-catalyzed dehydration, alcohols experience either E1 or E2 mechanisms that result in them losing water and thus forming a double molecular bond.

According to the University of California, Davis, the dehydration reaction of alcohols to create alkenes occurs through heating the alcohols at high temperatures in the presence of a strong acid, such as sulfuric or phosphoric acid. If the reaction isn't sufficiently heated, the alcohols don't dehydrate to form alkenes; instead, they react with each another to create ethers.

Although various types of alcohols may dehydrate through slightly distinct pathways, the reaction usually results in the alcohol donating two electrons from the acid reagent to form an alkyloxonium ion, according to Old Dominion. This ion serves as an effective leaving group that exits to create a carbocation, while the deprotonated acid then attacks the hydrogen molecule near the carbocation to form a double bond. Primary alcohols experience bimolecular elimination called E2 mechanism under this process, while secondary and tertiary alcohols experience unimolecular elimination or E1 mechanism.