Dehydration (chemistry)

In chemistry, dehydration means removing a molecule of water from a molecule or molecules containing hydrogen and oxygen. It includes both removal of a water molecule from one molecule (intramolecular dehydration), and a condensation reaction between two molecules that has water as a byproduct.

Dehydration is a chemical reaction. Removing water from a mixture like a solution is a different process called distillation or desiccation.

Hydrolysis, where water is added to break apart a molecule, is the opposite of condensation type dehydration. A desiccant can be used to remove water made by a dehydration reaction and avoid the reverse reactions.

Examples

Alcohols can be dehydrated using a strong acid (usually sulfuric acid) as a catalyst. Ethanol can go through both types of dehydration: intramolecular dehydration makes ethylene, and condensation makes diethyl ether.