What Is the Mechanism for Aldol Condensation?

The aldol condensation involves the reaction of a nucleophilic enolate with an electrophilic aldehyde or ketone. This reaction can be intermolecular or intramolecular and proceeds in the presence of a base.

The first step of the mechanism involves the formation of an enolate from an enolizable aldehyde or ketone in the presence of a strong base such as sodium hydroxide. Nucleophilic attack of the enolate on the carbonyl carbon of the electrophile forms a new carbon-carbon double bond and converts the carbonyl moiety of the electrophile to an alcohol. With heat, the alcohol undergoes base-catalyzed elimination to afford an alpha-beta unsaturated ketone.