cyanohydriner

Cyanohydriner, commonly called cyanohydrins, are a class of organic compounds that contain both a hydroxyl group and a nitrile group on the same carbon, with a general structure R2C(OH)CN for aldehyde- or ketone-derived examples. They form when a carbonyl compound (an aldehyde or ketone) reacts with hydrogen cyanide or a cyanide source, adding cyanide to the carbonyl carbon and protonating the oxygen to give the cyanohydrin.

Preparation and mechanism

Cyanohydrins are typically prepared by the nucleophilic addition of cyanide to carbonyl compounds in the presence of an acid or proton source. The reaction proceeds with the formation of a new C–CN and C–OH bond on the same carbon. Stereochemistry can be important for ketones that give two possible enantiomers, and enantioselective methods have been developed using chiral catalysts or auxiliaries.

Reactivity and transformations

Cyanohydrins are versatile intermediates in organic synthesis. They can be hydrolyzed to yield α-hydroxy acids (for example, mandelic acid from mandelonitrile). The cyanide group can be reduced to give amino alcohols, producing products with both an amino and an alcohol functionality. Cyanohydrins also serve as precursors to various natural products and pharmaceuticals.

Occurrence and safety

Natural cyanohydrins occur in some plants as components of cyanogenic glycosides (such as amygdalin). Upon enzymatic or acidic hydrolysis, they can release hydrogen cyanide, a highly toxic compound, so handling cyanohydrins requires appropriate safety precautions.

See also

Cyanohydrin formation is a foundational reaction in organic synthesis and is related to the preparation of α-hydroxy acids and amino alcohols.