Cyanohydrin
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In
organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, ...
, a cyanohydrin or hydroxynitrile is a
functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the re ...
found in
organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...
s in which a cyano and a hydroxy group are attached to the same carbon atom. The general formula is , where R is H,
alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl is derived from a cycloa ...
, or
aryl In organic chemistry, an aryl is any functional group or substituent derived from an aromaticity, aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar ...
. Cyanohydrins are industrially important precursors to carboxylic acids and some
amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...
s. Cyanohydrins can be formed by the cyanohydrin reaction, which involves treating a ketone or an
aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...
with hydrogen cyanide (HCN) in the presence of excess amounts of
sodium cyanide Sodium cyanide is a poisonous compound with the formula Na C N. It is a white, water-soluble solid. Cyanide has a high affinity for metals, which leads to the high toxicity of this salt. Its main application, in gold mining, also exploits its hi ...
(NaCN) as a catalyst: : In this reaction, the
nucleophilic In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...
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.


Acetone cyanohydrins

Acetone cyanohydrin Acetone cyanohydrin (ACH) is an organic compound used in the production of methyl methacrylate, the monomer of the transparent plastic polymethyl methacrylate (PMMA), also known as acrylic. It liberates hydrogen cyanide easily, so it is used as a s ...
, (CH3)2C(OH)CN is the cyanohydrin of
acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscib ...
. It is generated as an intermediate in the industrial production of methyl methacrylate. In the laboratory, this liquid serves as a source of HCN, which is inconveniently volatile. Thus, acetone cyanohydrin can be used for the preparation of other cyanohydrins, for the transformation of HCN to
Michael acceptor In organic chemistry, the Michael reaction or Michael addition is a reaction between a Michael donor (an enolate or other nucleophile) and a Michael acceptor (usually an α,β-unsaturated carbonyl) to produce a Michael adduct by creating a carbo ...
s, and for the formylation of
arene Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past groupin ...
s. Treatment of this cyanohydrin with
lithium hydride Lithium hydride is an inorganic compound with the formula Li H. This alkali metal hydride is a colorless solid, although commercial samples are grey. Characteristic of a salt-like (ionic) hydride, it has a high melting point, and it is not solub ...
affords anhydrous lithium cyanide: :


Preparative methods

Cyanohydrins were first prepared by the addition of HCN and a catalyst (base or enzyme) to the corresponding carbonyl. On a laboratory scale the use of HCN (toxic) is largely not encouraged, for this reason other less dangerous cyanation reagents are sought out. In situ formation of HCN can be sourced using precursors such as acetone cyanohydrin. Alternatively, cyano-silyl derivatives such as TMS-CN allows for both the cyanation and protection in one step without the need for HCN. Similar procedures relying on ester, phosphate and carbonate formation have been reported.


Other cyanohydrins

Mandelonitrile, with the formula C6H5CH(OH)CN, occurs in small amounts in the pits of some fruits. Related cyanogenic glycosides are known, such as
amygdalin Amygdalin (from Ancient Greek: ' "almond") is a naturally occurring chemical compound found in many plants, most notably in the seeds (kernels) of apricots, bitter almonds, apples, peaches, cherries, and plums. Amygdalin is classified as a cy ...
.
Glycolonitrile Glycolonitrile, also called hydroxyacetonitrile or formaldehyde cyanohydrin, is the organic compound with the formula HOCH2CN. It is the simplest cyanohydrin and it is derived from formaldehyde. It is a colourless liquid that dissolves in water an ...
, also called hydroxyacetonitrile or formaldehyde cyanohydrin, is the organic compound with the formula HOCH2CN. It is the simplest cyanohydrin, being derived from
formaldehyde Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section ...
. File:Glyconitrile Structural FormulaV1.svg, glycolonitrile File:Acetone cyanohydrin.svg, acetone cyanohydrin File:Mandelonitrile-2D-skeletal.svg, mandelonitrile


See also

* Halohydrin


References

{{Reflist


External links

*
IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
s
Gold Book The International Union of Pure and Applied Chemistry publishes many books which contain its complete list of definitions. The definitions are divided into seven "colour books": Gold, Green, Blue, Purple, Orange, White, and Red. There is also an e ...
definition of cyanohydrin

Functional groups