Cyanohydrin
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[[Image:Cyanohydrin.PNG|thumb|right|{size}|The structure of a typical cyanohydrin.]]
A '''cyanohydrin''' is a [[functional group]] in [[organic compound]]s. Cyanohydrins have the formula R<sub>2</sub>C(OH)CN, where R is H, [[alkyl]], or [[aryl]]. Cyanohydrins are industrially important precursors to [[carboxylic acid]]s including some [[amino acid]]s. 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:
:RR’C=O + HCN → RR’C(OH)CN
In this reaction, the [[nucleophilic]] CN<sup>−</sup> 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.<ref name=Corson>Corson, B. B.; Dodge, R. A.; Harris, S. A.; Yeaw, J. S. “Mandelic Acid” Organic Syntheses, Collected Volume 1, p.336 (1941). http://www.orgsyn.org/orgsyn/pdfs/CV1P0336.pdf. This paper describes the synthesis of mandelonitrile.</ref>
Cyanohydrins are intermediates in the [[Strecker amino acid synthesis]].
==Illustrative cyanohydrins==
Acetone cyanohydrin (CAS# 75-86-5, [[boiling point|b.p.]] 95 °C, also known as α-hydroxyisobutyronitrile), (CH<sub>3</sub>)<sub>2</sub>C(OH)CN is the cyanohydrin of [[acetone]]. This liquid serves as a source of HCN (which is a gas).<ref>Haroutounian, S. A. ”Acetone Cyanohydrin” Encyclopedia of Reagents for Organic Synthesis 2001, John Wiley & Sons. DOI: 10.1002/047084289X.ra014</ref> Thus, acetone cyanohydrin can be used for the preparation other cyanohydrins, for of HCN to [[Michael addition|Michael acceptor]]s, and for the [[Gattermann-Koch reaction|formylation]] of [[arene]]s. Treatment of this cyanohydrin with [[lithium hydride]] affords [[anhydrous]] lithium cyanide.
:(CH<sub>3</sub>)<sub>2</sub>C(OH)CN + LiH → LiCN + (CH<sub>3</sub>)<sub>2</sub>CO + H<sub>2</sub>
Mandelonitrile (CAS# 532-28-5, b.p. 170 °C) is the chemical compound with the formula [[phenyl|C<sub>6</sub>H<sub>5</sub>]]CH(OH)CN.<ref name=Corson/> Small amounts of this cyanohydrin occur in the pits of some fruits.
'''Glycolonitrile''', also called '''hydroxyacetonitrile''' or '''formaldehyde cyanohydrin''' (CAS#107-16-4), is the chemical compound with the formula HOCH<sub>2</sub>CN. It is the simplest cyanohydrin, being derived from [[formaldehyde]].<ref>Gaudry, R. “Glycolonitrile” Organic Syntheses, Collected Volume 3, p.436 (1955). http://www.orgsyn.org/orgsyn/pdfs/CV3P0436.pdf</ref>
==References==
<references/>
==External links==
*[[IUPAC]]s [[Gold Book]] definition of cyanohydrins [http://www.iupac.org/goldbook/C01489.pdf]
[[Category:functional groups]]
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