In aldol condensation, the enolate serves as a nucleophile, with its α carbon attacking the electrophilic carbonyl carbon of the aldehyde or ketone form also present in solution. Aldol condensation straddles both of the big categories of reactions of aldehydes and ketones. It involves both nucleophilic attack at the carbonyl carbon and electrophilic attack at the α-carbon.

The product of aldol addition is a β-hydroxy aldehyde or ketone, which readily undergoes dehydration to yield an αβ-unsaturated aldehyde or ketone.