Cyanide

In chemistry, a cyanide (from Greek kyanos'dark blue') is an inorganicchemical compound that contains a C≡Nfunctional group. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom.

Ionic cyanides contain the cyanide anionC≡N. This anion is extremely toxic and causes cyanide poisoning. Soluble cyanide salts such as sodium cyanide (NaCN), potassium cyanide (KCN) and tetraethylammonium cyanide ([(CH₃CH₂)₄N]CN) are also highly toxic.

Covalent cyanides contain the −C≡N group, and are usually called nitriles if the group is linked by a singlecovalent bond to carbon atom. For example, in acetonitrileCH₃−C≡N, the cyanide group is bonded to methyl−CH₃. In tetracyanomethaneC(−C≡N)₄, four cyano groups are bonded to carbon. Although nitriles generally do not release cyanide ions, the cyanohydrins do and are thus toxic. The cyano group may be covalently bonded to atoms other than carbon, e.g., in cyanogen azideN₃−C≡N, phosphorus tricyanideP(−C≡N)₃ and trimethylsilyl cyanide(CH₃)₃Si−C≡N.

Hydrogen cyanide, or H−C≡N, is a highly volatile toxic liquid that is produced on a large scale industrially. It is obtained by acidification of cyanide salts.