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Cyanogen chloride
IUPAC name
Other names Chloroformonitrile, Chlorine cyanide, Carbononitridic chloride, CK
CAS number 506-77-4 Yes check.svgY
PubChem 10477
EC number 208-052-8
UN number 1589
RTECS number GT2275000
Molecular formula CNCl
Molar mass 61.46 g/mol
Density 1.186 g/cm3 (liquid)
Melting point

−6 °C

Boiling point

12.7 °C [1]

Solubility in water Soluble
Vapor pressure 1987 kPa (21.1 °C)
Main hazards Highly toxic[2]
NFPA 704
NFPA 704.svg
Related compounds
Related cyanogen halides Cyanogen fluoride
Cyanogen bromide
Cyanogen iodide
Related compounds Cyanogen
 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Cyanogen chloride is an extremely toxic chemical compound with the formula CNCl. This linear, triatomic pseudohalogen is an easily condensed colorless gas. More commonly encountered in the laboratory is the related compound cyanogen bromide, a room temperature solid, and 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 compound, as are the related cyanogen halides (NCF, NCBr, NCI). Cyanogen chloride is produced by the oxidation of sodium cyanide with chlorine. This reaction proceeds via the intermediate cyanogen ((CN)2).[3]

NaCN + Cl2 → ClCN + NaCl

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

Cyanogen chloride is slowly hydrolyzed by water to release hydrogen cyanide

ClCN + H2O → HCN + HOCl

Applications in synthesis

CNCl is a precursor to the sulfonyl cyanides[4] and chlorosulfonyl isocyanate, a useful reagent in organic synthesis.[5]


Also known as CK, cyanogen chloride is a highly toxic blood agent, and was once proposed for use in chemical warfare. It causes immediate injury upon contact with the eyes or respiratory organs. Symptoms of exposure may include: loss of consciousness, convulsions, paralysis, rhinorrhea (runny nose), sore throat, drowsiness, confusion, nausea, vomiting, coughing, edema, and death[6]. 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[7].

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


  1. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0070494398
  2. ^
  3. ^ Coleman, G. H.; Leeper, R. W.; Schulze, C. C. "Cyanogen Chloride" Inorganic Syntheses McGraw-Hill: New York, 1946; Vol. 2, p. 90.
  4. ^ Vrijland, M. S. A. "Sulfonyl Cyanides: Methanesulfonyl Cyanide" Organic Syntheses, Collected Volume 6, p.727 (1988).
  5. ^ Graf, R. "Chlorosulfonyl Isocyanate" Organic Syntheses, Collected Volume 5, pages 226ff.
  6. ^
  7. ^ FM 3-8 Chemical Reference handbook; US Army; 1967

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