cyanate

A compound containing the OCN group, typically a salt or ester of cyanic acid (HOCN). The cyanate ion is ambidentate, that is, it has two reactive sites, because it can bind through the oxygen (O) or the nitrogen (N). Cyanate is commonly N-bonded with most nonmetallic elements, presumably because of the small charge density on the oxygen. Cyanic acid has the structure HO&dbnd;C&tbnd;N, but it may exist in an isomeric form known as isocyanic acid, HN&dbnd;C&dbnd;O. The cyanates are isomeric with fulminates, where the carbon and the nitrogen are transposed (ONC).

Cyanic acid is a volatile liquid, and it polymerizes upon standing to form cyamelide acid and cyanuric acid. In water cyanic acid undergoes hydrolysis to ammonia and carbon dioxide. However, dilute solutions in ice water may be kept for several hours. Both cyanic acid and isocyanic acid are prepared from cyanuric acid. The linear OCN ion may be prepared by mild oxidation of aqueous cyanide ion (CN⁻) using lead oxide (PbO) and potassium cyanide (KCN).

The primary use for cyanates is in the synthesis of a number of organic compounds such as unsubstituted carbamates (RNH&dbnd;C&dbnd;OOR′). These compounds are used as derivatives of alcohols. Other important reactions include addition to amines to give substituted ureas. See also Carbon; Cyanide.

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Space-filling model of the cyanate anion.

The cyanate ion is an anion consisting of one oxygen atom, one carbon atom, and one nitrogen atom, [OCN]⁻, in that order, and possesses 1 unit of negative charge, borne mainly by the nitrogen atom. In organic compounds the cyanate group is a functional group.

The structure of cyanate can be considered to resonate between two canonical forms:

The resonance hybrid resulting from these two contributory structures can be represented as

The cyanate ion is isoelectronic with carbon dioxide, and so shares its linear shape.

The cyanate ion is an ambident nucleophile in nucleophilic substitution because it can react to form an alkyl cyanate R-OCN (exception) or an alkyl isocyanate R-NCO (rule). Aryl cyanates (C₆H₅OCN) can be formed by a reaction of phenol with cyanogen chloride (ClCN) in the presence of a base.

Cyanates are salts or esters of cyanic acid, for example potassium cyanate (KOCN) or methyl cyanate. See also cyanate ester.

The cyanate ion is relatively non-toxic in comparison with cyanides. Use of this fact is made in cyanide decontamination processes where oxidants such as permanganate and hydrogen peroxide are used to convert toxic cyanide to safer cyanate.

The fulminate ion [ONC]⁻ has the same chemical formula but a different structure — it is a structural isomer of cyanate.

v • d • e Functional groups Chemical class: Alcohol • Aldehyde • Alkane • Alkene • Alkyne • Amide • Amine • Azo compound • Benzene derivative • Carboxylic acid • Cyanate • Disulfide • Ester • Ether • Haloalkane • Hydrazone • Imine • Isocyanide • Isocyanate • Ketone • Oxime • Nitrile • Nitro compound • Nitroso compound • Peroxide • Phosphoric acid • Pyridine derivative • Sulfone • Sulfonic acid • Sulfoxide • Thioester • Thioether • Thiol

v • d • e Inorganic compounds of carbon Oxides and related Oxides (CO2, CO) · Metal carbonyls · Carbonic acid · Bicarbonates · Carbonates Other ionic compounds Cyanides · Isocyanides · Cyanates · Thiocyanates · Isothiocyanates · Carbides

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