 Condensation reaction

A condensation reaction joins molecular units while eliminating a small molecule such as water or an alcohol. Formation of an ester from a carboxylic acid and an alcohol is a familiar example.

The term classifies the overall transformation, not one universal mechanism. In polycondensation, repeated joining can build a polymer while small molecules are released. An aldol condensation combines carbon-carbon bond formation with a subsequent elimination, so its full outcome must be distinguished from the initial aldol reaction.