A
cyanohydrin is a
functional groupIn organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...
found in
organic compoundAn organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
s. Cyanohydrins have the formula R
2C(OH)CN, where R is H, alkyl, or
arylIn the context of organic molecules, aryl refers to any functional group or substituent derived from an aromatic ring, be it phenyl, naphthyl, thienyl, indolyl, etc....
. Cyanohydrins are industrially important precursors to
carboxylic acidCarboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...
s and some
amino acidAmino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s. Cyanohydrins can be formed by the
cyanohydrin reactionA Cyanohydrin reaction is an organic chemical reaction by an aldehyde or ketone with a cyanide anion or a nitrile to form a cyanohydrin. This nucleophilic addition is a reversible reaction but with aliphatic carbonyl compounds equilibrium is in favor of the reaction products. The cyanide source...
, which involves treating a
ketoneIn organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...
or an
aldehydeAn aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
with
hydrogen cyanide (HCN) in the presence of excess amounts of
sodium cyanideSodium cyanide is an inorganic compound with the formula NaCN. This highly toxic colorless salt is used mainly in gold mining but has other niche applications...
(NaCN) as a catalyst:
- RR’C=O + HCN → RR’C(OH)CN
In this reaction, the nucleophilic CN
− 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
sulfiteSulfites are compounds that contain the sulfite ion SO. The sulfite ion is the conjugate base of bisulfite. Although the acid itself is elusive, its salts are widely used.-Structure:...
by cyanide salts:
Cyanohydrins are intermediates in the
Strecker amino acid synthesisThe Strecker amino acid synthesis, devised by Adolph Strecker, is a series of chemical reactions that synthesize an amino acid from an aldehyde . The aldehyde is condensed with ammonium chloride in the presence of potassium cyanide to form an α-aminonitrile, which is subsequently hydrolyzed to give...
.
Acetone cyanohydrins
Acetone cyanohydrinAcetone cyanohydrin is an organic compound used in the production of methyl methacrylate, the monomer of the transparent plastic polymethyl methacrylate , also known as acrylic.-Preparation:...
, (CH
3)
2C(OH)CN is the cyanohydrin of
acetoneAcetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
. It is generated as an intermediate in the industrial production of
methyl methacrylateMethyl methacrylate is an organic compound with the formula CH2=CCOOCH3. This colourless liquid, the methyl ester of methacrylic acid is a monomer produced on a large scale for the production of poly .-Production:...
. In the laboratory, this liquid serves as a source of HCN, which is inconveniently volatile. Thus, acetone cyanohydrin can be used for the preparation other cyanohydrins, for of HCN to Michael acceptors, and for the
formylationThe Gattermann–Koch reaction, named after the German chemists Ludwig Gattermann and Julius Arnold Koch, in organic chemistry refers to a Friedel–Crafts acylation reaction in which carbon monoxide and hydrochloric acid are used in situ with Friedel–Crafts catalyst, namely AlCl3 to produce a...
of
areneArene or Arênê or Arène may refer to:*an aromatic hydrocarbon*Arene , a genus of marine snails in the family Areneidae*Arene , the wife of Aphareus and mother of Idas and Lynceus in Greek mythology...
s. Treatment of this cyanohydrin with
lithium hydrideLithium hydride is the inorganic compound with the formula LiH. It is a colorless solid, although commercial samples are gray. Characteristic of a salt-like, or ionic, hydride, it has a high melting point and is not soluble in any solvent with which it does not react...
affords
anhydrousAs a general term, a substance is said to be anhydrous if it contains no water. The way of achieving the anhydrous form differs from one substance to another...
lithium cyanide:
Other cyanohydrins
MandelonitrileMandelonitrile is a chemical compound of the cyanohydrin class. Small amounts of mandelonitrile occur in the pits of some fruits.-Occurrence:...
, with the formula
C6H5CHIn organic chemistry, benzyl is the term used to describe the substituent or molecular fragment possessing the structure C6H5CH2-. Benzyl features a benzene ring attached to a CH2 group.-Nomenclature:...
(OH)CN, occurs in small amounts in the pits of some fruits. Related cyanogenic glycosides are known, such as
amygdalinAmygdalin , C20H27NO11, is a glycoside initially isolated from the seeds of the tree Prunus dulcis, also known as bitter almonds, by Pierre-Jean Robiquet...
.
GlycolonitrileGlycolonitrile, 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...
, also called hydroxyacetonitrile or formaldehyde cyanohydrin, is the organic compound with the formula HOCH
2CN. It is the simplest cyanohydrin, being derived from
formaldehydeFormaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...
.
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 |
 |
| glycolonitrile |
acetone cyanohydrin |
mandelonitrile |
External links
- IUPACs Gold Book
The Compendium of Chemical Terminology is a book published by the International Union of Pure and Applied Chemistry containing internationally accepted definitions for terms in chemistry...
definition of cyanohydrins http://www.iupac.org/goldbook/C01489.pdf