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Nitrosyl chloride
Names


IUPAC name Nitrosyl chloride
Identifiers
CAS Number	2696-92-6
3D model (JSmol)	Interactive image
ChemSpider	16641
ECHA InfoCard	100.018.430
EC Number	220-273-1
E number	E919 (glazing agents, ...)
MeSH	nitrosyl+chloride
PubChem CID	17601
RTECS number	QZ7883000
UNII	NHE5I1E5H6
UN number	1069
CompTox Dashboard (EPA)	DTXSID5051945
InChI InChI=1S/ClNO/c1-2-3Key: VPCDQGACGWYTMC-UHFFFAOYSA-N
SMILES ClN=O
Properties
Chemical formula	NOCl
Molar mass	65.459 g mol
Appearance	yellow gas
Density	2.872 mg mL
Melting point	−59.4 °C (−74.9 °F; 213.8 K)
Boiling point	−5.55 °C (22.01 °F; 267.60 K)
Solubility in water	Reacts
Structure
Molecular shape	Dihedral, digonal
Hybridisation	sp at N
Dipole moment	1.90 D
Thermochemistry
Std molar entropy (S₂₉₈)	261.68 J K mol
Std enthalpy of formation (Δ_fH₂₉₈)	51.71 kJ mol
Hazards
NFPA 704 (fire diamond)	3 0 1 W OX
Safety data sheet (SDS)	inchem.org
Related compounds
Related compounds	Nitroxyl Nitrosyl fluoride Nitrosyl bromide Nitryl chloride Chlorine nitrate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Y verify (what is ?) Infobox references

Chemical compound

Nitrosyl chloride is the chemical compound with the formula NOCl. It is a yellow gas that is commonly encountered as a component of aqua regia, a mixture of 3 parts concentrated hydrochloric acid and 1 part of concentrated nitric acid. It is a strong electrophile and oxidizing agent. It is sometimes called Tilden's reagent, after William A. Tilden, who was the first to produce it as a pure compound.

Structure and synthesis

The molecule is bent. A double bond exists between N and O (distance = 1.16 Å) and a single bond between N and Cl (distance = 1.96 Å). The O=N–Cl angle is 113°.

Production

Nitrosyl chloride can be produced in many ways.

Combining nitrosylsulfuric acid and HCl affords the compound. This method is used industrially.

HCl + NOHSO₄ → H₂SO₄ + NOCl

A more convenient laboratory method involves the (reversible) dehydration of nitrous acid by HCl

HNO₂ + HCl → H₂O + NOCl

By the direct combination of chlorine and nitric oxide; This reaction reverses above 100 °C.

Cl₂ + 2 NO → 2 NOCl

By reduction of nitrogen dioxide with hydrogen chloride:

2NO₂ + 4 HCl → 2NOCl + 2H₂O + Cl₂

Occurrence in aqua regia

NOCl also arises from the combination of hydrochloric and nitric acids according to the following reaction:

HNO₃ + 3 HCl → 2 + 2 H₂O + NOCl

In nitric acid, NOCl is readily oxidized into nitrogen dioxide. The presence of NOCl in aqua regia was described by Edmund Davy in 1831.

Reactions

NOCl behaves as an electrophile and an oxidant in most of its reactions. With halide acceptors it gives nitrosonium salts, and synthesis of nitrosonium tetrachloroferrate is typically performed in liquid NOCl:

NOCl + FeCl₃ →

In a related reaction, sulfuric acid gives nitrosylsulfuric acid, the mixed acid anhydride of nitrous and sulfuric acid:

ClNO + H₂SO₄ → ONHSO₄ + HCl

NOCl reacts with silver thiocyanate to give silver chloride and the pseudohalogen nitrosyl thiocyanate:

ClNO + AgSCN → AgCl + ONSCN

Similarly, it reacts with silver cyanide to give nitrosyl cyanide.

Nitrosyl chloride is used to prepare metal nitrosyl complexes. With molybdenum hexacarbonyl, NOCl gives the dinitrosyldichloride complex:

Mo(CO)₆ + 2 NOCl → MoCl₂(NO)₂ + 6 CO

It dissolves platinum:

Pt + 6 NOCl → (NO)₂ + 4 NO

Applications in organic synthesis

Aside from its role in the production of caprolactam, NOCl finds some other uses in organic synthesis. It adds to alkenes to afford α-chloro oximes. The addition of NOCl follows the Markovnikov rule. Ketenes also add NOCl, giving nitrosyl derivatives:

H₂C=C=O + NOCl → ONCH₂C(O)Cl

Carbonyl compounds enolize; and then NOCl attacks the nucleophilic end of the alkene to give a vicinal keto- or aldo-oxime.

Epoxides react with NOCl to give an α-chloronitritoalkyl derivatives. In the case of propylene oxide, the addition proceeds with high regiochemistry:

It converts amides to N-nitroso derivatives. NOCl converts some cyclic amines to the alkenes. For example, aziridine reacts with NOCl to give ethene, nitrous oxide and hydrogen chloride.

Industrial applications

NOCl and cyclohexane react photochemically to give cyclohexanone oxime hydrochloride. This process exploits the tendency of NOCl to undergo photodissociation into NO and Cl radicals. The cyclohexanone oxime is converted to caprolactam, a precursor to nylon-6.

Historical importance

Before the advent of modern spectroscopic methods for chemical analysis, informative chemical degradation and structure elucidation required the characterization of the individual components of various extracts. Notably, the aforementioned introduction of nitrosyl chloride by Tilden in 1875, as a reagent for producing crystalline derivatives of terpenes, e.g. α-pinene from oil of turpentine allowed investigators to readily distinguish one terpene from another.:

Safety

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

References

Tilden, William A. (1874). "XXXII.—On aqua regia and the nitrosyl chlorides". J. Chem. Soc. 27: 630–636. doi:10.1039/JS8742700630.
Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5.
^ Ritz, Josef; Fuchs, Hugo; Kieczka, Heinz; Moran, William C. (2002). "Caprolactam". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a05_031. ISBN 3527306730.
Morton, J. R.; Wilcox, H. W.; Moellerf, Therald; Edwards, Delwin C. (1953). "Nitrosyl Chloride". In Bailar, John C. Jr (ed.). Inorganic Syntheses. Vol. 4. McGraw-Hill. p. 48. doi:10.1002/9780470132357.ch16. ISBN 9780470132357.
Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 456. ISBN 978-0-08-037941-8.
Beckham, L. J.; Fessler, W. A.; Kise, M. A. (1951). "Nitrosyl Chloride". Chemical Reviews. 48 (3): 319–396. doi:10.1021/cr60151a001. PMID 24541207.
Edmund Davy (1830–1837). "On a New Combination of Chlorine and Nitrous Gas". Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London. 3: 27–29. JSTOR 110250.
Williams, D. L. H. (1988). Nitrosation. Cambridge, UK: Cambridge University. p. 11. ISBN 0-521-26796-X.
Kirby, G. W. (1977). "Tilden Lecture. Electrophilic C-Nitroso Compounds". Chemical Society Reviews. 6: 1. doi:10.1039/CS9770600001.
Johnson, B. F. G.; Al-Obadi, K. H. (1970). "Dihalogenodinitrosylmolybdenum and Dihalogenodinitrosyltungsten". Inorganic Syntheses. Vol. 12. pp. 264–266. doi:10.1002/9780470132432.ch47. ISBN 9780470132432. {{cite book}}: |journal= ignored (help)
Moravek, Richard T. (1986). "Nitrosyl Hexachloroplatinate(IV)". Inorganic Syntheses. Vol. 24. pp. 217–220. doi:10.1002/9780470132555.ch63. ISBN 9780470132555.
Ohno, M.; Naruse, N.; Terasawa, I. (1969). "7-Cyanoheptanal". Org. Synth. 49: 27. doi:10.15227/orgsyn.049.0027.
Williams 1988, p. 11.
Malinovskii, M. S.; Medyantseva, N. M. (1953). "Olefin Oxides. IX. Condensation of Olefin Oxides with Nitrosyl Chloride". Zhurnal Obshchei Khimii. 23: 84–6. (translated from Russian)
Van Leusen, A. M.; Strating, J. (1977). "p-Tolylsulfonyldiazomethane". Org. Synth. 57: 95. doi:10.15227/orgsyn.057.0095.
Williams 1988, p. 12.
Hanson, J.S. (2001). "The development of strategies for terpenoid structure determination". Natural Product Reports. 18 (6): 607–617. doi:10.1039/b103772m.