A condensation reaction (also known as a dehydration reaction) is a chemical reaction in which two molecules or moieties react with each other with the concurrent loss of water or ammonia. It may be considered as the opposite of a hydrolysis reaction, ie, the cleavage of a chemical entity into two parts by the action of water.

Mechanism

A condensation reaction proceeds in two steps:

1. Nucleophilic addition
2. Elimination

Applications

This type of reaction is used as a basis for the making of many important polymers for example: nylon, polyester and various epoxies. It is also the basis for the laboratory formation of silicates and polyphosphates. In biology, the formation of adenosine diphosphate and adenosine triphosphate from precursers and inorganic phosphate are also condensation reactions.

The reactions that form acid anhydrides from their constituent acids are typically condensation reactions.

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