Amides

Amides, chemical compounds consisting of an acid residue (acyl) and an amino group (NH₂). The greatest significance belongs to amides of organic acids, corresponding to the general formula R·CO·NH₂ (R-organic radical). They are obtained by the action of ammonia on anhydrides, chlorides, and esters of acids: 1) (RCO)₂O + NH₃ = R·CO·NH₂ + R·CO·OH; 2) R·CO·Cl + NH₃ = R·CO·NH₂ + HCl; 3) R·CO·OR + NH₃ = R·CO·NH₂ + ROH. The basic properties of the amino group in acid amides are significantly weakened due to the negative influence of the acid residue. Therefore, they form extremely unstable, easily hydrolyzing salts with acids, and the hydrogen of the amino group acquires the ability to be replaced by metals, i.e., acid amides are compounds of an amphoteric type. When heated with aqueous alkalis or acids, acid amides decompose into the corresponding acid and ammonia: R·CO·NH₂ + H₂O = R·CO·OH + NH₃, and when heated with dehydrating agents, they are converted into nitriles: R·CO·NH₂ = R·CN + H₂O. When one or both atoms of O in amides are replaced by alkyl or aryl groups, substituted or alkylated (arylated) amides are obtained. Of particular importance in biological processes is the diamide of carbonic acid-urea, CO(NH₂)₂, which is the end product of the transformation of protein substances in the bodies of animals.