In , organic chemistry, a cyanohydrin or hydroxynitrile is a functional group found in organic compounds in which a cyano and a hydroxy group are attached to the same carbon atom.  The general formula is , where R is H, alkyl, or aryl.  Cyanohydrins are industrially important precursors to carboxylic acids and some amino acids.  Cyanohydrins can be formed by the  cyanohydrin reaction, which involves treating a ketone or an aldehyde with hydrogen cyanide (HCN) in the presence of excess amounts of sodium cyanide (NaCN) as a catalyst:
In this reaction, the nucleophilic  ion attacks the electrophilic carbonyl carbon in the ketone, followed by protonation by HCN, thereby regenerating the cyanide anion.  Cyanohydrins are also prepared by displacement of sulfite by cyanide salts:
Cyanohydrins are intermediates in the Strecker amino acid synthesis.  In aqueous acid, they are hydrolyzed to the α-hydroxy acid.