Nitrosyl chloride

Nitrosyl chloride

Names
Preferred IUPAC name Nitrosyl chloride
Systematic IUPAC name Nitrooyl chloride
Other names Nitrogen oxychloride Nitrosonium chloride Tildens Reagent
Identifiers
CAS Number	2696-92-6 Y
3D model (JSmol)	Interactive image
ChemSpider	16641 Y
ECHA InfoCard	100.018.430
EC Number	220-273-1
E number	E919 (glazing agents, ...)
MeSH	nitrosyl+chloride
PubChem CID	17601
RTECS number	QZ7883000
UN number	1069
CompTox Dashboard (EPA)	DTXSID5051945
InChI InChI=1S/ClNO/c1-2-3 Y Key: VPCDQGACGWYTMC-UHFFFAOYSA-N Y
SMILES ClN=O
Properties
Chemical 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 (S⦵298)	261.68 kJ mol−1
Std enthalpy of formation (ΔfH⦵298)	51.71 kJ mol−1
Hazards
NFPA 704 (fire diamond)	3 0 1 W
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) 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

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°.

Production

As a simple, stable molecule, NOCl can be prepared in many ways. NOCl forms by the direct combination of chlorine and nitric oxide; this reaction reverses above 100 °C. Alternatively, nitrosylsulfuric acid and HCl also affords the compound:

HCl + NOHSO₄ → NOCl + H₂SO₄

This method is used industrially. A more convenient laboratory method involves the (reversible) dehydration of nitrous acid by HCl

Michael Faraday prepared nitrosyl chloride by reacting palladium with aqua regia:

Pd + HNO₃ + 3 HCl → PdCl₂ + ClNO + 2 H₂O

Another method of producing nitrosyl chloride is by direct union of the elements at 400 °C:

N₂ + O₂ + Cl₂ → 2 ClNO

Occurrence in aqua regia

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

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.

Reactions

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]⁺[SbCl₅]^-

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

ClNO + H₂SO₄ → ONHSO₄ + HCl

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

ClNO + AgSCN → AgCl + ONSCN

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 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:

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

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

Safety

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