Aromatic aldehydes and ketones undergo electrophilic substitution on the aromatic ring, where the carbonyl group acts as a deactivating and meta-directing group.

The Cannizzaro reaction involves self-oxidation and reduction (disproportionation) of aldehydes without an α-hydrogen atom when heated with concentrated alkali. Aldehydes lacking α-hydrogen atoms participate in this reaction.

Cross aldol condensation occurs when two different aldehydes or ketones react. If both have α-hydrogen atoms, it yields a mixture of four products. The aldol reaction of ethanal and propanal illustrates this when carried out in a mixture.

Aldol and ketol products formed in the Aldol reaction readily lose water to form α, β-unsaturated carbonyl compounds, and this reaction is known as Aldol condensation.

The Aldol reaction involves aldehydes and ketones with at least one α-hydrogen reacting in the presence of dilute alkali to form β-hydroxy aldehydes or β-hydroxy ketones. It is catalyzed by dilute alkali.