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IUPAC name
Other names Cyanogen
Carbon nitride
Oxalic acid dinitrile
Oxalyl cyanide
CAS number 460-19-5 Yes check.svgY
EC number 207-306-5
UN number 1026
RTECS number GT1925000
Molecular formula C2N2
Molar mass 52.04 g/mol
Density 0.95 g/cm3 (liquid, −21 °C)
Melting point

−28 °C

Boiling point

−21 °C

Solubility in water 450 ml/100 ml (20 °C)
EU Index 608-011-00-8
EU classification Flammable (F)
Very Toxic (T)
Dangerous for the environment (N)
R-phrases R11, R23, R50/53
S-phrases (S1/2), S23, S45, S60, S61
NFPA 704
NFPA 704.svg
Flash point Flammable gas
Explosive limits 6.6–42.6%
Related compounds
Related compounds Cyanogen fluoride
Cyanogen chloride
Cyanogen bromide
 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 is the chemical compound with the formula (CN)2. It is a colorless, 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, although other isomers have been detected.[1] Certain derivatives of cyanogen are also called “cyanogen” even though they contain only one CN group. For example cyanogen bromide has the formula NCBr.[2]

Cyanogen is the anhydride of oxamide:

H2NC(O)C(O)NH2 → NCCN + 2 H2O



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

2 Hg(CN)2 → (CN)2 + 2 HgCN

Alternatively, 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.[3]

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.[4]


Paracyanogen is produced by polymerization of cyanogen through pyrolysis of heavy metal cyanides. [5]


Cyanogen has a long history and was most likely generated first by Carl Scheele around 1782 while he was studying hydrogen cyanide.[6][7] The first confirmed synthesis was reported 1802, when it was used to make what is now known as cyanogen chloride. It attained importance with the growth of the fertilizer industry in the late nineteenth century and is still an important intermediate in the production of many fertilizers. It is also used as a stabilizer in the production of nitrocellulose.


Like other inorganic cyanides, cyanogen is very toxic, as it undergoes reduction to cyanide, which binds more strongly than oxygen to 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.[8]

Cyanogen produces the second hottest known natural flame (after carbon subnitride) with a temperature of over 4525°C (8180°F) when it burns in oxygen.[9]

See also


  1. ^ Ringer, Ashley (Jan 15), "Low-lying singlet excited states of isocyanogen", International Journal of Quantum Chemistry (Wiley) 106 (6): 1137–1140  
  2. ^ Hartman W. W.; Dreger, E. E. "Cyanogen Bromide" Organic Syntheses, Collected Volume 2, p.150 (1943).
  3. ^ T. K. Brotherton, J. W. Lynn (1959). "The Synthesis And Chemistry Of Cyanogen". Chemical Reviews 59 (5): 841–883. doi:10.1021/cr50029a003.  
  4. ^ A. A. Breneman (1959). "Showing the Progress and Development of Processes for the manufacture of Cyanogen and its Derivates (in: THE FIXATION OF ATMOSPHERIC NITROGEN". Journal of the American Chemical Society 11 (1): 2–28. doi:10.1021/ja02126a001.  
  5. ^ <a href="">Paracyanogen</a>
  6. ^ H. Bauer (1980). "Die ersten organisch-chemischen Synthesen". Naturwissenschaften 67 (1): 1–6. doi:10.1007/BF00424496.  
  7. ^ J. Gay-Lussac (1815). "?". Ann. Chim. Et phys. 96: 175.  
  8. ^ Muir, GD (ed.) 1971, Hazards in the Chemical Laboratory, The Royal Institute of Chemistry, London.
  9. ^ Thomas, N.; Gaydon, A. G.; Brewer, L. (March 1952), "Cyanogen Flames and the Dissociation Energy of N2", The Journal of Chemical Physics 20 (3): 369–374, doi:10.1063/1.1700426,  

External links


1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

CYANOGEN (Gr. Kuavos, blue -yevvav, to produce), C2N2, in chemistry, a gas composed of carbon and nitrogen. The name was suggested by Prussian blue, the earliest known compound of cyanogen. It was first isolated in 1815 by J. GayLussac, who obtained it by heating mercury or silver cyanide; this discovery is of considerable historical importance, since it recorded the isolation of a "compound radical." It may also be prepared by heating ammonium oxalate; by passing induction sparks between carbon points in an atmosphere of nitrogen (see H. von Wartenburg, Abs. J.C.S., 1907, i. p. 299), or by the addition of a concentrated solution of potassium cyanide to one of copper sulphate, the mixed solutions being then heated. It also occurs in blast-furnace gases. When cyanogen is prepared by heating mercuric cyanide, a residue known as para-cyanogen, (CN)x, is left; this is to be regarded as a polymer of cyanogen. It is a brownish amorphous solid, which is insoluble in water. Cyanogen is a colourless gas, possessing a peculiar characteristic smell, and is very poisonous. It burns with a purple flame, forming carbon dioxide and nitrogen; and may be condensed (by cooling to - 25° C.) to a colourless liquid, and further to a solid, which melts at - 34.4° C. (M. Faraday, Ann., 18 45, 56, p. 158). It dissolves readily in water and the aqueous solution decomposes on standing; a dark-brown flocculent precipitate of azulmic acid, C 4 H 5 N 5 0, separating whilst ammonium oxalate, urea and hydrocyanic acid are found in the solution. In many respects it resembles chlorine in its chemical behaviour, a circumstance noted by Gay-Lussac; it combines directly with hydrogen (at 50o° to 550° C.) to form hydrocyanic acid, and with chlorine, bromine, iodine and sulphur, to form cyanogen chloride, &c.; it also combines directly with zinc, cadmium and iron to form cyanides of these metals. It combines with sulphuretted hydrogen, in the .presence of water, to form the compound C 2 N 2 H 2 S, and in the presence of alcohol, to form the compound C 2 N 2.2H 2 S. Concentrated hydrochloric acid converts it into oxamide. Potash solution converts it into a mixture of potassium cyanide and cyanate. When heated with hydriodic acid (specific gravity 1.96) it forms amino-acetic acid, and with tin and hydrochloric acid it yields ethylene diamine.

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