Any member of either of two classes of nitrogen -containing organic compounds related to ammonia and amines and containing a carbonyl group ( 2015; C 003D; O; see functional group ).
The first class, covalent amides are formed by replacing the hydroxyl group ( 2015; OH) of an acid with an amino group ( 2015; NR 2 , in which R may represent a hydrogen atom or an organic combining group, such as methyl). Amides formed from carboxylic acids , called carboxamides, are solids except for the simplest, formamide, a liquid. They do not conduct electricity, have high boiling points, and (when liquid) are good solvents . There are no practical natural sources of simple covalent amides, but the peptides and proteins in living systems are long chains ( polymers ) with peptide bonds (see covalent bond ), which are amide linkages. Urea is an amide with two amino groups. Commercially important covalent amides include several used as solvents; others are the sulfa drugs and nylon . The second class, ionic (salt-like) amides (see ionic bond ), are made by treating a covalent amide, an amine, or ammonia with a reactive metal (e.g., sodium) and are strongly alkaline.