Cyanogen chloride

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Cyanogen chloride
Skeletal formula of cyanogen chloride
Ball and stick model of cyanogen chloride Spacefill model of cyanogen chloride
Abbreviations CK
CAS number 506-77-4 YesY
PubChem 10477
ChemSpider 10045 YesY
EC number 208-052-8
UN number 1589
MeSH cyanogen+chloride
RTECS number GT2275000
Jmol-3D images Image 1
Molecular formula CNCl
Molar mass 61.470 g mol−1
Appearance Colorless gas
Odor acrid
Density 2.7683 mg mL−1 (at 0 °C, 101.325 kPa)
Melting point −6.55 °C (20.21 °F; 266.60 K)
Boiling point 13 °C (55 °F; 286 K)
Solubility in water soluble
Solubility soluble in ethanol, ether
Vapor pressure 1.987 MPa (at 21.1 °C)
236.33 J K−1 mol−1
137.95 kJ mol−1
Main hazards Highly toxic[2]
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 4: Very short exposure could cause death or major residual injury. E.g., VX gas Reactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorus Special hazards (white): no codeNFPA 704 four-colored diamond
Related compounds
Related alkanenitriles
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Cyanogen chloride is an inorganic compound with the formula NCCl. 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 that is widely used in biochemical analysis and preparation.

Synthesis, basic properties, structure[edit]

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 molecule, as are the related cyanogen halides (NCF, NCBr, NCCI). 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 trimerizes in the presence of acid to the heterocycle called cyanuric chloride.

Cyanogen chloride is slowly hydrolyzed by water to release hydrogen cyanide

ClCN + H2O → HCN + HOCl

Applications in synthesis[edit]

Cyanogen chloride 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 drowsiness, rhinorrhea (runny nose), sore throat, coughing, confusion, nausea, vomiting, edema, loss of consciousness, convulsions, paralysis, and death.[2] 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.[6]

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


  1. ^ Lide, David R., ed. (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, FL: CRC Press. ISBN 0-8493-0487-3. 
  2. ^ a b "CYANOGEN CHLORIDE (CK)". The Emergency Response Safety and Health Database. NIOSH. 
  3. ^ Coleman, G. H.; Leeper, R. W.; Schulze, C. C. (1946). "Cyanogen Chloride". Inorganic Syntheses 2: 90–94. doi:10.1002/9780470132333.ch25. 
  4. ^ Vrijland, M. S. A. (1977), "Sulfonyl Cyanides: Methanesulfonyl Cyanide", Org. Synth. 57: 88 ; Coll. Vol. 6: 727 
  5. ^ Graf, R. (1966), "Chlorosulfonyl Isocyanate", Org. Synth. 46: 23 ; Coll. Vol. 5: 226 
  6. ^ FM 3-8 Chemical Reference Handbook. US Army. 1967. 

External links[edit]