Aldol reaction

Aldol Reaction

The Aldol reaction is a fundamental organic chemistry reaction, first reported by Charles-Adolphe Wurtz in 1872. It involves the addition of a carbon nucleophile to a carbonyl group, resulting in a β-hydroxy carbonyl compound, or 'aldol' (aldehyde + alcohol), from which the reaction gets its name.

Mechanism

The aldol reaction can proceed via two fundamentally different mechanisms: the aldol addition and the aldol condensation. The former involves the addition of a nucleophilic enolate ion to a carbonyl compound to form a β-hydroxy carbonyl compound. The latter involves the dehydration of the aldol product to form an α,β-unsaturated carbonyl compound.

Aldol Addition

In the aldol addition, a base is used to deprotonate the α-carbon of a carbonyl compound, forming an enolate ion. This enolate ion then acts as a nucleophile, attacking the carbonyl carbon of a second molecule of the carbonyl compound. The resulting product is a β-hydroxy carbonyl compound, or 'aldol'.

Aldol Condensation

In the aldol condensation, the aldol product undergoes dehydration to form an α,β-unsaturated carbonyl compound. This can occur spontaneously under the reaction conditions, or can be induced by the addition of an acid or heat.

Applications

The aldol reaction is widely used in organic synthesis, for the formation of carbon-carbon bonds. It is also a key step in many biological processes, including the glycolysis pathway and the citric acid cycle.

See Also

• Claisen condensation
• Michael reaction
• Robinson annulation