Dehydration synthesis, or a dehydration reaction, is a chemical reaction associated with the loss of a water molecule between two compounds. Dehydration synthesis is a type of condensation reaction, which is what occurs when two molecules join to make a larger molecule while losing a small molecule.
Typical dehydrating agents in organic synthesis are sulfuric acid, concentrated phosphoric acid or hot aluminum oxide. However, because of the complexity of some of the reactions, experiments must be performed in well-ventilated areas because the steam produced could be dangerous. What occurs during hydrolysis, or a hydration reaction, is the opposite of the events of a dehydration reaction.