Nitrosyl chloride

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Nitrosyl chloride
Skeletal formula of nitrosyl chloride with measurements
Spacefill model of nitrosyl chloride
Identifiers
CAS number 2696-92-6 YesY
PubChem 17601
ChemSpider 16641 YesY
EC number 220-273-1
UN number 1069
MeSH nitrosyl+chloride
RTECS number QZ7883000
Jmol-3D images Image 1
Properties
Molecular formula NOCl
Molar mass 65.459 g mol−1
Appearance Yellow gas
Density 2.872 mg mL−1
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 sp2 at N
Dipole moment 1.90 D
Thermochemistry
Std molar
entropy
So298
261.68 J K-1 mol−1
Std enthalpy of
formation
ΔfHo298
51.71 kJ mol−1
Hazards
MSDS inchem.org
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazard W: Reacts with water in an unusual or dangerous manner. E.g., cesium, sodiumNFPA 704 four-colored diamond
Related compounds
Related compounds
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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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. It is a strong electrophile and oxidizing agent.

Structure and synthesis[edit]

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 = 1.69 Å). The O-N-Cl angle is 113°.[1]

Production[edit]

Since nitrosyl chloride is chemically simple and stable at room temperature and below, it can be produced in many ways.

HCl + NOHSO4H2SO4 + NOCl
  • A more convenient laboratory method involves the (reversible) dehydration of nitrous acid by HCl[3]
HNO2 + 2HCl → H2O + NOCl
Pd + HNO3 + 3 HCl → PdCl2 + 2 H2O + NOCl
  • NOCl forms by the direct combination of chlorine and nitric oxide; This reaction reverses above 100 °C.
Cl2 + 2NO → 2NOCl
  • Another method of producing nitrosyl chloride is by direct union of the elements at 400 °C, although there is some regression as above.
N2 + O2 + Cl2 → 2 NOCl ↔ 2NO + Cl2

Occurrence in aqua regia[edit]

NOCl also arises from the combination of hydrochloric and nitric acids according to the following reaction:[4]

HNO3 + 3 HCl → Cl2 + 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.[5]

Reactions[edit]

NOCl behaves as an electrophile and an oxidant in most of its reactions. With halide acceptors, for example antimony pentachloride, converts to nitrosonium salts:

NOCl + SbCl5 → [NO]+[SbCl6]-

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

Applications in organic synthesis[edit]

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.[6] The initial addition of NOCl follows the Markovnikov rule. Ketenes also add NOCl, giving nitrosyl derivatives:

CH2C=C=O + NOCl → ONCH2C(O)Cl

Propylene oxide also undergoes electrophilic addition with NOCl to give an α-chloro-nitritoakyl derivative:

Electrophilic addition of NOCl to propylene oxide.png

At ambient temperatures, NOCl converts cyclic amines to the alkenes. For example, aziridine reacts with NOCl to give ethene, nitrous oxide and hydrogen chloride.

Industrial applications[edit]

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 oxide is converted to caprolactam, a precursor to Nylon-6.[2]

Safety[edit]

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

References[edit]

  1. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  2. ^ a b Josef Ritz, Hugo Fuchs, Heinz Kieczka, William C. Moran "Caprolactam" Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. doi:10.1002/14356007.a05_031
  3. ^ J. R. Morton, H. W. Wilcox "Nitrosyl Chloride" Inorganic Syntheses 1953, vol. 48-52. doi:10.1002/9780470132357.ch16
  4. ^ L. J. Beckham, W. A. Fessler, M. A. Kise (1951). "Nitrosyl Chloride". Chemical Reviews 48 (3): 319–396. doi:10.1021/cr60151a001. 
  5. ^ Edmund Davy (1830–1837). "On a New Combination of Chlorine and Nitrous Gas. [Abstract]". Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London, Vol. 3. (JSTOR): 27–29. JSTOR 110250. 
  6. ^ Ohno, M,; Naruse, N.; Terasawa, I. (1973), "7-cyanoheptanal", Org. Synth. ; Coll. Vol. 5: 266