Cyanogen chloride

Cyanogen chloride is a chemical compound with the formula CNCl. This linear triatomic pseudohalogen is an easily condensed colorless gas. More commonly enountered in the laboratory is the related species cyanogen bromide, a room temperature solid, which is widely used in biochemical analysis and preparation.

Synthesis, basic properties, structure
Although the formula is written CNCl, cyanogen chloride is a molecule with the connectivity ClCN. Carbon and chlorine are linked by a single bond and carbon and nitrogen by a triple bond. It is a linear species, as are the related cyanogen halides (NCF, NCBr, NCI). Cyanogen chloride is prepared by oxidation of sodium cyanide with chlorine. This reaction proceeds via the intermediacy of cyanogen ((CN)2).
 * NaCN +  Cl2  →  ClCN  +  NaCl

The compound is molecular, although polar. It trimerizes in the presence of acid to the heterocyclic trimer called cyanuric chloride.

Applications in synthesis
CNCl is a precursor to sulfonyl cyanides. and chlorosulfonyl isocyanate, a useful reagent in organic synthesis.

Safety
Also known as CK, cyanogen chloride is a highly toxic blood agent, once proposed for use in chemical warfare. It causes immediate injury upon contact with the eyes or respiratory organs. Symptoms of exposure are loss of consciousness, convulsions, paralysis, and death. It is especially dangerous because it is capable of penetrating the filters in gas masks, according to U.S. analysts. CK is unstable due to polymerization, sometimes with explosive violence.

Cyanogen chloride is listed in schedule 3 of the Chemical Weapons Convention: all production must be reported to the OPCW.