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Nitrosyl chloride
Nitrosyl chloride
Nitrosyl chloride
IUPAC name
Other names Nitrogen oxychloride
Nitrosonium chloride
CAS number 2696-92-6 Yes check.svgY
UN number 1069
RTECS number QZ7883000
Molecular formula ClNO
Molar mass 65.46 g/mol
Appearance yellow gas, red liquid
Density 1.273 g/cm3 (liquid, -12 °C)
2.872 g/L (gas)
Melting point

-59.4 °C

Boiling point

-5.55 °C

Solubility in water decomposes
Solubility in chlorocarbons soluble
Molecular shape sp2 at N
Dipole moment 1.90 D
EU Index Not listed
Main hazards Highly toxic
NFPA 704
NFPA 704.svg
Related compounds
Other anions Nitrosyl fluoride
Nitrosyl bromide
Other cations Thionyl chloride
Related compounds Nitric oxide
Nitrosylsulfuric acid
Nitrosyl fluoroborate
Thionitrosyl chloride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Nitrosyl chloride is the chemical compound NOCl. It is a yellow gas that is most commonly encountered as a decomposition product of aqua regia, a mixture of hydrochloric acid and nitric acid. The related nitrosyl halides nitrosyl fluoride, NOF, and nitrosyl bromide, NOBr, are also known.


Structure and synthesis

Although its formula is written NOCl, the structure is better represented ONCl. A double bond exists between N and O (distance = 1.16 Å) and a single bond between N and Cl (distance = 1.69 Å). The O-N-Cl angle is 113°.[1]

NOCl can be prepared by the direct combination of chlorine and nitric oxide. Alternatively, nitrosylsulfuric acid and HCl also affords the compound:

HCl + NOHSO4 → NOCl + H2SO4

It also arises from the combination of hydrochloric and nitric acids according to the following reaction:[2]

HNO3 + 3 HCl → Cl2 + 2 H2O + NOCl

Although this mixture was used for dissolving gold for a long time the first description of the gas was done by Edmund Davy in 1831.[3]


  • NOCl reacts with halide acceptors to give the nitrosyl cation, [NO]+. This species is available as NOBF4.
  • NOCl reacts with water to release HCl.
  • Heating NOCl above 100°C gives back Cl2 and NO.
  • In organic synthesis, NOCl is often employed. It adds to alkenes to afford α-chloro oximes.[4]
  • NOCl photolyses to NO and a Cl radical.


NOCl is very toxic and irritating to the lungs, eyes and skin.


  1. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  2. ^ L. J. Beckham, W. A. Fessler, M. A. Kise (1951). "Nitrosyl Chloride". Chemical Reviews 48: 319–396. doi:10.1021/cr60151a001.  
  3. ^ Edmund Davy (1830 - 1837). Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London, Vol. 3.. pp. 27–29.  
  4. ^ Ohno, M,; Naruse, N.; Terasawa, I. (1973), "7-cyanoheptanal", Org. Synth.,  ; Coll. Vol. 5: 266  


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