(i) Aldol condensation :
Aldol and Ketol lose water to provide α,β-unsaturated carbonyl compounds which are aldol condensation products.
(ii) Cannizzaro reaction:
Aldehydes without α-hydrogen atom undergo self-oxidation and reduction reaction when treated with concentrated alkali.
(iii) Hell-Volhard-Zelinsky (HVZ )reaction:
Carboxylic acids having a α-hydrogen are halogenated at the α-position giving α-halo carboxylic acids on treatment with chlorine or bromine in the presence of small amount of red phosphorus.
(iv) Friedel-Crafts acylation reaction:
We get acyl benzene when an acyl halide is reacted with benzene in the presence of Lewis acids.
