Cyanogen chloride is a highly 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 that is widely used in biochemical analysis and preparation.

Cyanogen chloride
Skeletal formula of cyanogen chloride
Ball and stick model of cyanogen chloride
Ball and stick model of cyanogen chloride
Spacefill model of cyanogen chloride
Spacefill model of cyanogen chloride
Preferred IUPAC name
Carbononitridic chloride
Systematic IUPAC name
Other names
  • Chlorine cyanide
  • Cyanic chloride
  • Chlorocyanogen
  • Chlorcyan
  • Chlorocyanide
3D model (JSmol)
Abbreviations CK
ECHA InfoCard 100.007.321 Edit this at Wikidata
EC Number
  • 208-052-8
MeSH cyanogen+chloride
RTECS number
  • GT2275000
UN number 1589
  • InChI=1S/CClN/c2-1-3 checkY
  • ClC#N
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 soluble in ethanol, ether
Vapor pressure 1.987 MPa (at 21.1 °C)
-32.4·10−6 cm3/mol
236.33 J K−1 mol−1
137.95 kJ mol−1
Occupational safety and health (OHS/OSH):
Main hazards
Highly toxic;[2] forms cyanide in the body[3]
GHS labelling:
GHS04: Compressed Gas GHS05: Corrosive GHS06: Toxic GHS09: Environmental hazard
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 0: Will not burn. E.g. waterInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazards (white): no code
Flash point nonflammable[3]
NIOSH (US health exposure limits):
PEL (Permissible)
REL (Recommended)
C 0.3 ppm (0.6 mg/m3)[3]
IDLH (Immediate danger)
Safety data sheet (SDS)
Related compounds
Related alkanenitriles
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Synthesis, basic properties, structure Edit

Cyanogen chloride is a molecule with the connectivity Cl−C≡N. 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, NCI). Cyanogen chloride is produced by the oxidation of sodium cyanide with chlorine. This reaction proceeds via the intermediate cyanogen ((CN)2).[4]


The compound trimerizes in the presence of acid to the heterocycle called cyanuric chloride.

Cyanogen chloride is slowly hydrolyzed by water at neutral pH to release cyanate and chloride ions:


Applications in synthesis Edit

Cyanogen chloride is a precursor to the sulfonyl cyanides[5] and chlorosulfonyl isocyanate, a useful reagent in organic synthesis.[6]

Safety Edit

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 United States analysts. CK is unstable due to polymerization, sometimes with explosive violence.[7]

Chemical weapon Edit

Cyanogen chloride is listed in schedule 3 of the Chemical Weapons Convention: all production must be reported to the OPCW.[8]

By 1945, the U.S. Army's Chemical Warfare Service developed chemical warfare rockets intended for the new M9 and M9A1 Bazookas. An M26 Gas Rocket was adapted to fire cyanogen chloride-filled warheads for these rocket launchers.[9] As it was capable of penetrating the protective filter barriers in some gas masks,[10] it was seen as an effective agent against Japanese forces (particularly those hiding in caves or bunkers) because their standard issue gas masks lacked the barriers that would provide protection against cyanogen chloride.[9][11][12] The US added the weapon to its arsenal, and considered using it, along with hydrogen cyanide, as part of Operation Downfall, the planned invasion of Japan, but President Harry Truman decided against it, instead using the atomic bombs developed by the secret Manhattan Project.[13] The CK rocket was never deployed or issued to combat personnel.[9]

References Edit

  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. 9 July 2021.
  3. ^ a b c d e NIOSH Pocket Guide to Chemical Hazards. "#0162". National Institute for Occupational Safety and Health (NIOSH).
  4. ^ Coleman, G. H.; Leeper, R. W.; Schulze, C. C. (1946). "Cyanogen Chloride". Inorganic Syntheses. Inorganic Syntheses. Vol. 2. pp. 90–94. doi:10.1002/9780470132333.ch25. ISBN 9780470132333.
  5. ^ Vrijland, M. S. A. (1977). "Sulfonyl Cyanides: Methanesulfonyl Cyanide" (PDF). Organic Syntheses. 57: 88.; Collective Volume, vol. 6, p. 727
  6. ^ Graf, R. (1966). "Chlorosulfonyl Isocyanate" (PDF). Organic Syntheses. 46: 23.; Collective Volume, vol. 5, p. 226
  7. ^ FM 3-8 Chemical Reference Handbook. US Army. 1967.
  8. ^ "Schedule 3". Retrieved 16 March 2018.
  9. ^ a b c Smart, Jeffrey (1997), "2", History of Chemical and Biological Warfare: An American Perspective, Aberdeen, MD, USA: Army Chemical and Biological Defense Command, p. 32.
  10. ^ "Cyanogen chloride (CK): Systemic Agent | NIOSH | CDC". 9 July 2021.
  11. ^ "Characteristics and Employment of Ground Chemical Munitions", Field Manual 3-5, Washington, DC: War Department, 1946, pp. 108–19
  12. ^ Skates, John R (2000), The Invasion of Japan: Alternative to the Bomb, University of South Carolina Press, pp. 93–96, ISBN 978-1-57003-354-4
  13. ^ Binkov's Battlegrounds (27 April 2022). "How would have WW2 gone if the US had not used nuclear bombs on Japan?". YouTube.Com. Retrieved 23 June 2022.

External links Edit