Aldehydes and ketones condense in basic media to form aldols. This reaction is called aldol condensation.

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The aldol formed dehydrates in the basic medium by heating to form an a , b -unsaturated.

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The aldol condensation mechanism occurs with the formation of an enolate, which attacks the carbonyl of another molecule. In this condensation, a carbon-carbon bond is formed between the carbonyl of one molecule and the a- carbon of the other.

Stage 1. Formation of the enolate

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The base depotates the alpha carbon of the ethanal, generating the resonance-stabilized enolate.

Stage 2. Nucleophilic attack of the enolate on the carbonyl

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Stage 3. Protonation

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Step 4. Dehydration of the aldol

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