An aldol reaction takes the following form:

2 enolate anions ↔ aldol

The reaction requires a base catalyst. The aldol produced is a β-hydroxyaldehyde or a β-hydroxyketone.

An aldol reaction is a condensation reaction.

An aldol reaction forms a carbon-carbon bond.

Mechanism

The mechanism has 3 steps:

1. base + aldehyde or ketone ↔ water + resonance-stabilized enolate anion
2. aldehyde or ketone + enolate anion ↔ tetrahedral carbonyl addition intermediate
3. tetrahedral carbonyl addition intermediate + proton donor ↔ aldol + base