Cyanohydrins

General formula of the cyanohydrins (R ¹ and R ² are hydrogen atoms or organyl radicals (alkyl radical, alkenyl radical, aryl radical, alkylaryl radical, etc.)). The cyanohydrin group is marked in blue .

Example: acetone cyanohydrin . The cyanohydrin group is marked in blue .

Cyanohydrins (synonym: α-hydroxynitriles) contain, bonded to the same carbon atom, one hydroxyl and one nitrile group , and can therefore be referred to as geminal hydroxynitriles. They arise from the addition reaction of hydrocyanic acid to the carbonyl group of aldehydes or ketones . The semi-structural formula of the cyanohydrins is R – CH (OH) –CN (R = alkyl or aryl radical ) if the synthesis was based on an aldehyde. From ketones R ₂ C = O and hydrocyanic acid, on the other hand, cyanohydrins with the semi- structural formula R ₂ C (OH) -CN are obtained. Enantiomerically pure ( R ) -cyanohydrins can be obtained directly from aldehydes using the enzyme ( R ) - oxynitrilase .

The cyanohydrins are starting materials for a number of important organic substances. Acid hydrolysis of cyanohydrins produces α- hydroxycarboxylic acids ( lactic acid , mandelic acid, etc.).

In addition, cyanohydrins play a role as intermediate stages of the benzoin addition and the Kiliani-Fischer synthesis .

Individual evidence

1. ^ ^{A b} Hans Beyer and Wolfgang Walter : Textbook of Organic Chemistry , S. Hirzel Verlag, Stuttgart, 1991, 22nd edition ISBN 3-7776-0485-2 , p. 555.
2. ^ CG Kruse: Chiral Cyanohydrins - Their Manufacture and Utility as Chiral Building Blocks p. 10, in: Chirality in Industry , editors: AN Collins, GN Sheldrake and J. Crosby, Wiley, 1992, ISBN 0-471-93595-6 .