Question

Write mechanism of Aldol addition reaction.

Explain the mechanism of aldol addition reaction

Answer 1

Aldol addition reaction:-

'Aldol' is an abbreviation of aldehyde and alcohol. When the enolate of an aldehyde or a ketone reacts at the α-carbon with the carbonyl of another molecule under basic or acidic conditions to obtain β-hydroxy aldehyde or ketone, the reaction is called an aldol reaction.

Step I: Base OH− ion abstracts a hydrogen atom from an α-carbon of aldehyde to form carbanion.

Step II: The nucleophilic carbanion or enolate ion attacks the electrophilic carbonyl carbon of the second aldehyde molecule to form an intermediate alkoxide ion. A new C–C bond is formed.

Step III: Alkoxide ion abstracts a hydrogen ion from water to form β-hydroxy aldehyde. Base OH− ion is regenerated.