Amides

Amides contain the functional group -CONH₂: a carbonyl group bonded directly to a nitrogen atom. They are named from the parent carboxylic acid by replacing "-oic acid" with "-amide", so CH₃CONH₂ is ethanamide.If one hydrogen on the nitrogen is replaced by an alkyl or aryl group, the compound is an N-substituted amide, such as N-methylethanamide, CH₃CONHCH₃.Formation. Amides are made by reacting an acyl chloride with ammonia in a nucleophilic addition-elimination reaction. A second ammonia molecule reacts with the HCl formed:CH₃COCl + 2NH₃ → CH₃CONH₂ + NH₄ClUsing an amine instead of ammonia gives an N-substituted amide.Properties. Unlike amines, amides are not basic. The nitrogen lone pair is delocalised onto the neighbouring carbonyl group, so it is not available to accept a proton. Amides form hydrogen bonds through their N-H and C=O groups, so simple amides such as ethanamide are solids at room temperature.Hydrolysis. The C-N bond can be broken by heating under reflux with acid or alkali:CH₃CONH₂ + H₂O + H⁺ → CH₃COOH + NH₄⁺CH₃CONH₂ + OH⁻ → CH₃COO⁻ + NH₃With acid, the carboxylic acid and ammonium ions form; with alkali, the carboxylate ion forms and ammonia gas is given off. The same link, -CONH-, holds polyamides and proteins together.