Aldol Condensation

Aldehydes and ketones containing alpha-H atom undergo a reversible self -addition in presence of dilute alkali to give condensation product, beta-hydroxy aldehyde and ketone

Mechanism of the Aldol condensation

Here the carbanion (2) obtained from the action of base on an alpha-H atom of one molecule of carbonyl compound (1) adds to the carbonyl carbon of another aldehyde to yeild a beta-hydroxy aldehyde (3).

Aldol condensation
Mechanism aldol condensation (Base catalysed)