nitriles of hydroxy acids; organic compounds containing one hydroxyl (—OH) group and one cyano (—C≡N) group—for example, the nitrile of γ-hydroxybutyric acid, HOCH2CH2CH2C≡ N. The most accessible hydroxynitriles are α-hydroxynitriles (cyanohydrins), in which both functional groups are bonded to the same carbon atom, and β-hydroxynitriles, in which the –OH and –CN groups are bonded to the neighboring carbon atoms. The α- and β-hydroxynitriles are produced by reaction of carboxylic compounds and olefin oxides, respectively, with hydrocyanic acid, HCN, in the presence of alkaline catalysts. The simplest α-hydroxynitriles— for example, the nitrile of glycolic acid, HOCH2CN; the nitrile of lactic acid, CH3CH(OH)CN; and acetone cyanohydrin, (CH3)2C(OH)CN—are colorless liquids that are readily soluble in water and organic solvents.
Hydroxynitriles are highly reactive compounds. For example, α-hydroxynitriles form hydroxy acids upon saponification and aminonitriles upon interaction with NH3 (the latter products are readily converted into amino acids through hydrolysis), and β-hydroxynitriles can be readily dehydrated to form unsaturated nitriles, such as ethylene cyanohydrin, HOCH2—CH2CN. The formation of hydroxynitriles is the basis for the synthesis of such important monomers as acrylonitrile, acrylic acid, and methacrylic acid and their corresponding esters, as well as for the synthesis of amino acids and monosaccharides. Acetone cyanohydrin is a source of 2,2-azobisisobutyronitrile, an initiator of free radical reactions that is used as a blowing agent (Porophor N).