selfcondensation

Selfcondensation, in chemistry, refers to a reaction in which two identical molecules react with each other to form a larger product, typically with the loss of a small molecule such as water or a simple alcohol. The term covers homodimerization or homopolymerization processes and is used across organic synthesis and polymer chemistry to describe how a molecule can connect with itself to build more complex structures.

In organic reactions, self-condensation often proceeds via formation of an enolate or other active nucleophile on one molecule that attacks the carbonyl of a second molecule of the same species. The classic example is the aldol self-condensation of aldehydes or ketones bearing an α-hydrogen under basic or acidic catalysis, yielding a β-hydroxy carbonyl compound that can dehydrate to an α,β-unsaturated carbonyl compound. Water removal or use of dehydrating conditions shifts the equilibrium toward the condensed product.

In polymer chemistry, self-condensation describes condensation polymerization where difunctional monomers react with other molecules of the same monomer, forming polymers with the loss of small molecules such as water. Examples include polyester and polyamide formation from bifunctional monomers, in which hydroxyl-carboxyl or amine-carboxyl groups react stepwise to stitch monomer units into long chains.

Self-condensation is a key strategy in carbon–carbon bond formation and material synthesis, but controlling selectivity and preventing side reactions can be challenging. The term emphasizes the role of identical reactants in generating larger products, rather than reactions between different species.