Cyanohydrin

Last updated
The structure of a general cyanohydrin. Cyanohydrin-general-2D-skeletal.png
The structure of a general cyanohydrin.

In , organic chemistry, a cyanohydrin or hydroxynitrile is a functional group found in organic compounds in which a cyano and a hydroxy group are attached to the same carbon atom. The general formula is R2C(OH)CN, where R is H, alkyl, or aryl. Cyanohydrins are industrially important precursors to carboxylic acids and some amino acids. 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: [1]

Contents

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 sulfite by cyanide salts: [2]

Cyanation of aldehyde with bisulfate.svg

Cyanohydrins are intermediates in the Strecker amino acid synthesis. In aqueous acid, they are hydrolyzed to the α-hydroxy acid.

Acetone cyanohydrins

Acetone cyanohydrin, (CH3)2C(OH)CN is the cyanohydrin of acetone. It is generated as an intermediate in the industrial production of methyl methacrylate. [3] In the laboratory, this liquid serves as a source of HCN, which is inconveniently volatile. [4] Thus, acetone cyanohydrin can be used for the preparation of other cyanohydrins, for the transformation of HCN to Michael acceptors, and for the formylation of arenes. Treatment of this cyanohydrin with lithium hydride affords anhydrous lithium cyanide:

LiCN-from-acetone-cyanohydrin-2D-skeletal.png

Preparative methods

Cyanohydrins were first prepared by the addition of HCN and a catalyst (base or enzyme) to the corresponding carbonyl. [5] 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. [6] Similar procedures relying on ester, phosphate and carbonate formation have been reported. [7] [8] [9]

Different reactions for the preparation of cyanohydrin Cyanohydrin synthesis.jpg
Different reactions for the preparation of cyanohydrin

Other cyanohydrins

Mandelonitrile, with the formula C6H5CH(OH)CN, occurs in small amounts in the pits of some fruits. [2] Related cyanogenic glycosides are known, such as amygdalin. [1]

Amygdalin is one of several naturally occurring cyanogenic glycosides. Amygdalin structure.svg
Amygdalin is one of several naturally occurring cyanogenic glycosides.

Glycolonitrile, also called hydroxyacetonitrile or formaldehyde cyanohydrin, is the organic compound with the formula HOCH2CN. It is the simplest cyanohydrin, being derived from formaldehyde. [10]

See also

Related Research Articles

<span class="mw-page-title-main">Aldehyde</span> Organic compound containing the functional group R−CH=O

In organic chemistry, an aldehyde is an organic compound containing a functional group with the structure R−CH=O. The functional group itself can be referred to as an aldehyde but can also be classified as a formyl group. Aldehydes are a common motif in many chemicals important in technology and biology.

<span class="mw-page-title-main">Hydrazone</span> Organic compounds - Hydrazones

Hydrazones are a class of organic compounds with the structure R1R2C=N−NH2. They are related to ketones and aldehydes by the replacement of the oxygen =O with the =N−NH2 functional group. They are formed usually by the action of hydrazine on ketones or aldehydes.

Mesitylene or 1,3,5-trimethylbenzene is a derivative of benzene with three methyl substituents positioned symmetrically around the ring. The other two isomeric trimethylbenzenes are 1,2,4-trimethylbenzene (pseudocumene) and 1,2,3-trimethylbenzene (hemimellitene). All three compounds have the formula C6H3(CH3)3, which is commonly abbreviated C6H3Me3. Mesitylene is a colorless liquid with sweet aromatic odor. It is a component of coal tar, which is its traditional source. It is a precursor to diverse fine chemicals. The mesityl group (Mes) is a substituent with the formula C6H2Me3 and is found in various other compounds.

In organic chemistry, a nitrile is any organic compound that has a −C≡N functional group. The name of the compound is composed of a base, which includes the carbon of the −C≡N, suffixed with "nitrile", so for example CH3CH2C≡N is called "propionitrile". The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, including methyl cyanoacrylate, used in super glue, and nitrile rubber, a nitrile-containing polymer used in latex-free laboratory and medical gloves. Nitrile rubber is also widely used as automotive and other seals since it is resistant to fuels and oils. Organic compounds containing multiple nitrile groups are known as cyanocarbons.

In organic chemistry, hydrocyanation is a process for conversion of alkenes to nitriles. The reaction involves the addition of hydrogen cyanide and requires a catalyst. This conversion is conducted on an industrial scale for the production of precursors to nylon.

The Fischer oxazole synthesis is a chemical synthesis of an oxazole from a cyanohydrin and an aldehyde in the presence of anhydrous hydrochloric acid. This method was discovered by Emil Fischer in 1896. The cyanohydrin itself is derived from a separate aldehyde. The reactants of the oxazole synthesis itself, the cyanohydrin of an aldehyde and the other aldehyde itself, are usually present in equimolar amounts. Both reactants usually have an aromatic group, which appear at specific positions on the resulting heterocycle.

A cyanohydrin reaction is an organic chemical reaction in which an aldehyde or ketone reacts 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 can be potassium cyanide, sodium cyanide or trimethylsilyl cyanide. With aromatic aldehydes such as benzaldehyde, the benzoin condensation is a competing reaction. The reaction is used in carbohydrate chemistry as a chain extension method for example that of D-xylose.

The Strecker amino acid synthesis, also known simply as the Strecker synthesis, is a method for the synthesis of amino acids by the reaction of an aldehyde with cyanide in the presence of ammonia. The condensation reaction yields an α-aminonitrile, which is subsequently hydrolyzed to give the desired amino acid. The method is used for the commercial production of racemic methionine from methional.

The Gattermann reaction (also known as the Gattermann formylation and the Gattermann salicylaldehyde synthesis) is a chemical reaction in which aromatic compounds are formylated by a mixture of hydrogen cyanide (HCN) and hydrogen chloride (HCl) in the presence of a Lewis acid catalyst such as aluminium chloride (AlCl3). It is named for the German chemist Ludwig Gattermann and is similar to the Friedel–Crafts reaction.

<span class="mw-page-title-main">Trimethylsilyl cyanide</span> Chemical compound

Trimethylsilyl cyanide is the chemical compound with the formula (CH3)3SiCN. This volatile liquid consists of a cyanide group, that is CN, attached to a trimethylsilyl group. The molecule is used in organic synthesis as the equivalent of hydrogen cyanide. It is prepared by the reaction of lithium cyanide and trimethylsilyl chloride:

In chemistry, transfer hydrogenation is a chemical reaction involving the addition of hydrogen to a compound from a source other than molecular H2. It is applied in laboratory and industrial organic synthesis to saturate organic compounds and reduce ketones to alcohols, and imines to amines. It avoids the need for high-pressure molecular H2 used in conventional hydrogenation. Transfer hydrogenation usually occurs at mild temperature and pressure conditions using organic or organometallic catalysts, many of which are chiral, allowing efficient asymmetric synthesis. It uses hydrogen donor compounds such as formic acid, isopropanol or dihydroanthracene, dehydrogenating them to CO2, acetone, or anthracene respectively. Often, the donor molecules also function as solvents for the reaction. A large scale application of transfer hydrogenation is coal liquefaction using "donor solvents" such as tetralin.

<span class="mw-page-title-main">Zinc cyanide</span> Chemical compound

Zinc cyanide is the inorganic compound with the formula Zn(CN)2. It is a white solid that is used mainly for electroplating zinc but also has more specialized applications for the synthesis of organic compounds.

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 source of such. For this reason, this cyanohydrin is also highly toxic.

The Bucherer–Bergs reaction is the chemical reaction of carbonyl compounds or cyanohydrins with ammonium carbonate and potassium cyanide to give hydantoins. The reaction is named after Hans Theodor Bucherer.

In organic chemistry, a homologation reaction, also known as homologization, is any chemical reaction that converts the reactant into the next member of the homologous series. A homologous series is a group of compounds that differ by a constant unit, generally a methylene group. The reactants undergo a homologation when the number of a repeated structural unit in the molecules is increased. The most common homologation reactions increase the number of methylene units in saturated chain within the molecule. For example, the reaction of aldehydes or ketones with diazomethane or methoxymethylenetriphenylphosphine to give the next homologue in the series.

In organic synthesis, cyanation is the attachment or substitution of a cyanide group on various substrates. Such transformations are high-value because they generate C-C bonds. Furthermore nitriles are versatile functional groups.

<span class="mw-page-title-main">Mandelonitrile</span> Chemical compound

In organic chemistry, mandelonitrile is the nitrile of mandelic acid, or the cyanohydrin derivative of benzaldehyde. Small amounts of mandelonitrile occur in the pits of some fruits.

Nitrile anions is jargon from the organic product resulting from the deprotonation of alkylnitriles. The proton(s) α to the nitrile group are sufficiently acidic that they undergo deprotonation by strong bases, usually lithium-derived. The products are not anions but covalent organolithium complexes. Regardless, these organolithium compounds are reactive toward various electrophiles.

In organic chemistry, alkynylation is an addition reaction in which a terminal alkyne is added to a carbonyl group to form an α-alkynyl alcohol.

<span class="mw-page-title-main">MoOPH</span> Chemical compound

MoOPH, also known as oxodiperoxymolybdenum(pyridine)-(hexamethylphosphoric triamide), is a reagent used in organic synthesis. It contains a molybdenum(VI) center with multiple oxygen ligands, coordinated with pyridine and HMPA ligands. It is an electrophilic source of oxygen that reacts with enolates and related structures, and thus can be used for alpha-hydroxylation of carbonyl-containing compounds. Other reagents used for alpha-hydroxylation via enol or enolate structures include Davis oxaziridine, oxygen, and various peroxyacids. This reagent was first utilized by Edwin Vedejs as an efficient alpha-hydroxylating agent in 1974 and an effective preparative procedure was later published in 1978.

References

  1. 1 2 David T. Mowry (1948). "The Preparation of Nitriles". Chem. Rev. 42 (2): 189–283. doi:10.1021/cr60132a001. PMID   18914000.
  2. 1 2 Corson, B. B.; Dodge, R. A.; Harris, S. A.; Yeaw, J. S. (1941). "Mandelic Acid". Organic Syntheses ; Collected Volumes, vol. 1, p. 336.
  3. William Bauer, Jr. "Methacrylic Acid and Derivatives" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi : 10.1002/14356007.a16_441. Article Online Posting Date: June 15, 2000
  4. Haroutounian, S. A. "Acetone Cyanohydrin" Encyclopedia of Reagents for Organic Synthesis 2001, John Wiley & Sons. doi : 10.1002/047084289X.ra014
  5. North, M.; Usanov, D. L.; Young, C. Lewis Acid Catalyzed Asymmetric Cyanohydrin Synthesis. Chem. Rev. 2008, 108 (12), 5146–5226. doi:10.1021/cr800255k.
  6. Lidy, W.; Sundermeyer, W. Spaltungsreaktionen Des Trimethylsilylcyanids, Eine Neue Darstellungsmethode Für O-(Trimethylsilyl)Cyanhydrine. Chem. Ber. 1973, 106 (2), 587–593. doi:10.1002/cber.19731060224
  7. Scholl, M.; Lim, C. K.; Fu, G. C. Convenient and Efficient Conversion of Aldehydes to Acylated Cyanohydrins Using Tributyltin Cyanide as a Catalyst. J. Org. Chem. 1995, 60 (19), 6229–6231. doi: 10.1021/jo00124a052.
  8. Yoneda, R.; Harusawa, S.; Kurihara, T. Cyano Phosphate: An Efficient Intermediate for the Chemoselective Conversion of Carbonyl Compounds to Nitriles. J. Org. Chem. 1991, 56 (5), 1827–1832. doi: 10.1021/jo00005a031.
  9. Juhl, M.; Petersen, A. R.; Lee, J.-W. CO2‐Enabled Cyanohydrin Synthesis and Facile Iterative Homologation Reactions. Chem. – A Eur. J. 2020. doi: 10.1002/chem.202003623.
  10. Gaudry, R. (1955). "Glycolonitrile". Organic Syntheses ; Collected Volumes, vol. 3, p. 436.