Carboxylic acids contain the carboxyl functional group, -COOH, which consists of a carbonyl group attached to a hydroxyl group.

Aldehydes and ketones serve as solvents, starting materials, and reagents in the chemical industry. Examples include formaldehyde used in preserving biological specimens and making bakelite, acetaldehyde in the production of acetic acid and polymers, and benzaldehyde in perfumery and dye ...

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.