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Cyanogen
Ball and stick model of cyanogen	Spacefill model of cyanogen
Names
	Preferred IUPAC name Oxalonitrile
	Systematic IUPAC name Ethanedinitrile
	Other names Cyanogen; Bis(nitridocarbon)(C—C); Dicyan; Carbon nitride; Oxalic acid dinitrile; Dicyanogen; Nitriloacetonitrile; CY
Identifiers
CAS Number	460-19-5 ;
3D model (JSmol)	Interactive image;
Beilstein Reference	1732464
ChEBI	CHEBI:29308 ;
ChemSpider	9605 ;
ECHA InfoCard	100.006.643
EC Number	207-306-5;
Gmelin Reference	1090
MeSH	cyanogen
PubChem CID	9999;
RTECS number	GT1925000;
UNII	534Q0F66RK ;
UN number	1026
CompTox Dashboard (EPA)	DTXSID1023992 ;
	InChI InChI=1S/C2N2/c3-1-2-4 Key: JMANVNJQNLATNU-UHFFFAOYSA-N ;
	SMILES N#CC#N;
Properties
Chemical formula	C2N2
Molar mass	52.036 g·mol−1
Appearance	Colourless gas
Odor	pungent, bitter almond-like
Density	950 mg mL−1 (at −21 °C)
Melting point	−28 °C (−18 °F; 245 K)
Boiling point	−21.1 °C; −6.1 °F; 252.0 K
Solubility in water	45 g/100 mL (at 20 °C)
Solubility	soluble in ethanol, ethyl ether
Vapor pressure	5.1 atm (21 °C)
Henry's law; constant (kH)	1.9 μmol Pa−1 kg−1
Magnetic susceptibility (χ)	-21.6·10−6 cm3/mol
Refractive index (nD)	1.327 (18 °C)
Thermochemistry
Std molar; entropy (S⦵298)	241.57 J K−1 mol−1
Std enthalpy of; formation (ΔfH⦵298)	309.07 kJ mol−1
Std enthalpy of; combustion (ΔcH⦵298)	−1.0978–−1.0942 MJ mol−1
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	forms cyanide in the body; flammable
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H220, H331, H410
Precautionary statements	P210, P261, P271, P273, P304+P340, P311, P321, P377, P381, P391, P403, P403+P233, P405, P501
NFPA 704 (fire diamond)	4 4 2
Explosive limits	6.6–32%
	NIOSH (US health exposure limits):
PEL (Permissible)	none
REL (Recommended)	TWA 10 ppm (20 mg/m3)
IDLH (Immediate danger)	N.D.
Safety data sheet (SDS)	inchem.org
Related compounds
Related alkanenitriles	Hydrogen cyanide; Thiocyanic acid; Cyanogen iodide; Cyanogen bromide; Cyanogen chloride; Cyanogen fluoride; Cyanogen azide; Acetonitrile; Aminoacetonitrile; Glycolonitrile; Propionitrile; Aminopropionitrile; Malononitrile; Pivalonitrile; Acetone cyanohydrin;
Related compounds	DBNPA
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Cyanogen is the chemical compound with the formula (C N)₂. The simplest stable carbon nitride, it is a colorless and highly toxic gas with a pungent odor. The molecule is a pseudohalogen. Cyanogen molecules consist of two CN groups ‒ analogous to diatomic halogen molecules, such as Cl₂, but far less oxidizing. The two cyano groups are bonded together at their carbon atoms: N≡C‒C≡N, though other isomers have been detected.^[6] The name is also used for the CN radical,^[7] and hence is used for compounds such as cyanogen bromide (NCBr)^[8] (but see also Cyano radical). When burned at increased pressure with oxygen, it is possible to get a blue tinted flame, the temperature of which is about 4800°C (a higher temperature is possible with ozone). It is as such regarded as the gas with the second highest temperature of burning (after dicyanoacetylene).

Cyanogen is the anhydride of oxamide:

H₂NC(O)C(O)NH₂ → NCCN + 2 H₂O

though oxamide is manufactured from cyanogen by hydrolysis:^[9]

NCCN + 2 H₂O → H₂NC(O)C(O)NH₂

Preparation

Cyanogen is typically generated from cyanide compounds. One laboratory method entails thermal decomposition of mercuric cyanide:

2 Hg(CN)₂ → (CN)₂ + Hg₂(CN)₂

Or, one can combine solutions of copper(II) salts (such as copper(II) sulfate) with cyanides; an unstable copper(II) cyanide is formed which rapidly decomposes into copper(I) cyanide and cyanogen.^[10]

2 CuSO₄ + 4 KCN → (CN)₂ + 2 CuCN + 2 K₂SO₄

Industrially, it is created by the oxidation of hydrogen cyanide, usually using chlorine over an activated silicon dioxide catalyst or nitrogen dioxide over a copper salt. It is also formed when nitrogen and acetylene are reacted by an electrical spark or discharge.^[11]

Isomers

Cyanogen is NCCN. There are less stable isomers in which the order of the atoms differs. Isocyanogen (or cyanoisocyanogen) is NCNC, diisocyanogen is CNNC, and diazodicarbon^{[citation needed]} is CCNN.

Paracyanogen

Paracyanogen is a polymer of cyanogen. It can be best prepared by heating mercury(II) cyanide. It can also be prepared by heating silver cyanide, silver cyanate, cyanogen iodide or cyanuric iodide.^[12] It can also be prepared by the polymerization of cyanogen at 300 to 500 °C (572 to 932 °F) in the presence of trace impurities. Paracyanogen can also be converted back to cyanogen by heating to 800 °C (1,470 °F).^[9] Based on experimental evidence, the structure of this polymeric material is thought to be rather irregular, with most of the carbon atoms being of sp² type and localized domains of π conjugation.^[13]

History

Cyanogen was first synthesized in 1815 by Joseph Louis Gay-Lussac, who determined its empirical formula and named it. Gay-Lussac coined the word "cyanogène" from the Greek words κυανός (kyanos, blue) and γεννάω (gennao, to create), because cyanide was first isolated by Swedish chemist Carl Wilhelm Scheele from the pigment Prussian blue.^[14] It attained importance with the growth of the fertilizer industry in the late 19th century and remains an important intermediate in the production of many fertilizers. It is also used as a stabilizer in the production of nitrocellulose.

Cyanogen is commonly found in comets.^[15] In 1910 a spectroscopic analysis of Halley's Comet found cyanogen in the comet's tail, which led to public fear that the Earth would be poisoned as it passed through the tail. People in New York wore gas masks, and merchants sold quack "comet pills" claimed to neutralize poisoning.^[15] Because of the extremely diffuse nature of the tail, there was no effect when the planet passed through it.^[16]^[17]

Safety

Like other cyanides, cyanogen is very toxic, as it readily undergoes reduction to cyanide, which poisons the cytochrome c oxidase complex, thus interrupting the mitochondrial electron transfer chain. Cyanogen gas is an irritant to the eyes and respiratory system. Inhalation can lead to headache, dizziness, rapid pulse, nausea, vomiting, loss of consciousness, convulsions, and death, depending on exposure.^[18] Lethal dose through inhalation typically ranges from 100 to 150 milligrams (1.5 to 2.3 grains).

Cyanogen produces the second-hottest-known natural flame (after dicyanoacetylene aka carbon subnitride) with a temperature of over 4,525 °C (8,177 °F) when it burns in oxygen.^[19]^[20]

In popular culture

In the Doctor Who serial "The Brain of Morbius" (the 5th serial of season 13), the Doctor synthesizes cyanogen using hydrogen cyanide as a starting material and vents it through a pipe to stop Solon from performing surgery on the brain of Morbius's body.

In Dragnet (1987) Friday (Dan Aykroyd) and Streebek (Tom Hanks) are tracking down the villain who stole "the pseudohalogenic compound cyanogen".^[21]

References

^ "oxalonitrile (CHEBI:29308)". Chemical Entities of Biological Interest. UK: European Bioinformatics Institute. 27 October 2006. Main. Retrieved 6 June 2012.
^ ^a ^b NIOSH Pocket Guide to Chemical Hazards. Department of Health and Human Services, Centers for Disease Control, National Institute for Occupational Safety & Health. September 2007. p. 82.
^ ^a ^b The Merck Index (10th ed.). Rahway, NJ: Merck & Co. 1983. p. 385. ISBN 9780911910278.
^ ^a ^b "Front Matter". Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: Royal Society of Chemistry. 2014. p. 902. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
^ ^a ^b ^c ^d ^e ^f NIOSH Pocket Guide to Chemical Hazards. "#0161". National Institute for Occupational Safety and Health (NIOSH).
^ Ringer, A. L.; Sherrill, C. D.; King, R. A.; Crawford, T. D. (2008). "Low-lying singlet excited states of isocyanogen". International Journal of Quantum Chemistry. 106 (6): 1137–1140. Bibcode:2008IJQC..108.1137R. doi:10.1002/qua.21586.
^ Irvine, William M. (2011). "Cyanogen Radical". Encyclopedia of Astrobiology. p. 402. doi:10.1007/978-3-642-11274-4_1806. ISBN 978-3-642-11271-3.
^ Hartman, W. W.; Dreger, E. E. (1931). "Cyanogen Bromide" (PDF). Organic Syntheses. 11: 30; Collected Volumes, vol. 2, p. 150.
^ ^a ^b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 320–321. ISBN 978-0-08-037941-8.
^ Brotherton, T. K.; Lynn, J. W. (1959). "The Synthesis And Chemistry Of Cyanogen". Chemical Reviews. 59 (5): 841–883. doi:10.1021/cr50029a003.
^ Breneman, A. A. (January 1889). "The Fixation of Atmospheric Nitrogen". Journal of the American Chemical Society. 11 (1): 2–27. doi:10.1021/ja02126a001.
^ Bircumshaw, L. L.; F. M. Tayler; D. H. Whiffen (1954). "Paracyanogen: its formation and properties. Part I". J. Chem. Soc.: 931–935. doi:10.1039/JR9540000931.
^ Maya, Leon (1993). "Paracyanogen Reexamined". Journal of Polymer Science Part A (Submitted manuscript). 31 (10): 2595–2600. Bibcode:1993JPoSA..31.2595M. doi:10.1002/pola.1993.080311020.
^ Gay-Lussac, J. L. (1815). "Recherches sur l'acide prussique". Annales de Chimie (in French). 95: 136–231. Gay-Lussac names cyanogen on p. 163.
^ ^a ^b "Cometary Poison Gas Geyser Heralds Surprises". science.nasa.gov. 2010-11-02. Archived from the original on 2010-11-06.
^ "Comet's Poisonous Tail" (PDF). New York Times. 1910-02-08.
^ "Halley's Comet 100 years ago". The Denver Post. 2010-05-25.
^ Muir, G. D., ed. (1971). Hazards in the Chemical Laboratory. London: The Royal Institute of Chemistry.
^ Thomas, N.; Gaydon, A. G.; Brewer, L. (1952). "Cyanogen Flames and the Dissociation Energy of N₂". The Journal of Chemical Physics. 20 (3): 369–374. Bibcode:1952JChPh..20..369T. doi:10.1063/1.1700426.
^ J. B. Conway; R. H. Wilson Jr.; A. V. Grosse (1953). "The Temperature of the Cyanogen-Oxygen Flame". Journal of the American Chemical Society. 75 (2): 499. doi:10.1021/ja01098a517.
^ "The trichlornitromethane and the pseudo-halogenic compound cyanogen". Retrieved August 18, 2021.