Aldol Condensation
The Aldol Condensation is one of the most fundamental carbon-carbon-bond forming reactions in organic synthesis. Two carbonyl compounds, each of which may be either an aldehyde or a ketone, undergo a base-promoted condensation to afford an α,β-unsaturated carbonyl compound.
The reaction takes place in two stages. First, the enol form of one of the carbonyl compounds attacks the non-enolized carbonyl carbon atom of the second compound. This results in the formation of a β-hydroxy carbonyl compound. In the second stage, the intermediate tautomerizes to the enol form and a molecule of water is eliminated. This second step is possible only if the first enolizable compound possesses two hydrogen atoms on a carbon adjacent to the carbonyl because it must be able to tautomerize to the enol form twice. If only one such hydrogen atom is present, the reaction can proceed no farther than the β-hydroxy carbonyl compound.
