Phosgene oxime

Names
Preferred IUPAC name 1,1-Dichloro-N-hydroxymethanimine
Other names dichloroformaldoxime, dichloroformoxime, hydroxycarbonimidic dichloride, CX, dichloroformaldehyde oxime
Identifiers
CAS Number	1794-86-1 Y
3D model (JSmol)	Interactive image
ChemSpider	59024 Y
PubChem CID	65582
UNII	G45S3149SQ Y
CompTox Dashboard (EPA)	DTXSID9075292
InChI InChI=1S/CHCl2NO/c2-1(3)4-5/h5H Y Key: JIRJHEXNDQBKRZ-UHFFFAOYSA-N Y InChI=1/CHCl2NO/c2-1(3)4-5/h5H Key: JIRJHEXNDQBKRZ-UHFFFAOYAP
SMILES Cl/C(Cl)=N\O
Properties
Chemical formula	CHCl2NO
Molar mass	113.93 g·mol−1
Appearance	colorless or white solid
Melting point	35 to 40 °C (95 to 104 °F; 308 to 313 K)[1]
Boiling point	128 °C (262 °F; 401 K)[1]
Solubility in water	70%[1]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Highly toxic
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Phosgene oxime, or CX, is an organic compound with the formula Cl₂CNOH. It is a potent chemical weapon, specifically a nettle agent, which is a type of blister agent. The compound itself is a colorless solid, but impure samples are often yellowish liquids. It has a strong, disagreeable and irritating odor. It is used as a reagent in organic chemistry.^[2]

Preparation and reactions

Phosgene oxime can be prepared by reduction of chloropicrin using a combination of tin metal and hydrochloric acid as the source of the active hydrogen reducing acent:

Cl₃CNO₂ + 4 [H] → Cl₂C=N−OH + HCl + H₂O

The observation of a transient violet color in the reaction suggests intermediate formation of trichloronitrosomethane (Cl₃CNO). Early preparations, using stannous chloride as the reductant, also started with chloropicrin.^[3]

The compound is electrophilic and thus sensitive to nucleophiles, including bases, which destroy it:

Cl₂CNOH + 2 NaOH → CO₂ + NH₂OH + 2 NaCl + H₂O

Phosgene oxime has been used to prepare heterocycles that contain N-O bonds, such as isoxazoles.^[4]

Dehydrohalogenation upon contact with mercuric oxide generates cyanoformyl chloride, a reactive nitrile oxide:^[5]

Cl₂CNOH → ClCNO + HCl

Toxicity

Phosgene oxime is classified as a vesicant even though it does not produce blisters.^[6] It is toxic by inhalation, ingestion, or skin contact. The effects of the poisoning occur almost immediately. No antidote for phosgene oxime poisoning is known. Generally, any treatment is supportive. Typical physical symptoms of CX exposure are as follows:

• Skin: Blanching surrounded by an erythematous ring can be observed within 30 seconds of exposure. A wheal develops on exposed skin within 30 minutes. The original blanched area acquires a brown pigmentation by 24 hours. An eschar forms in the pigmented area by 1 week and sloughs after approximately 3 weeks. Initially, the effects of CX can easily be misidentified as mustard gas exposure. However, the onset of skin irritation resulting from CX exposure is a great deal faster than mustard gas, which typically takes several hours or more to cause skin irritation.
• Eyes: Eye examination typically demonstrates conjunctivitis, lacrimation, lid edema, and blepharospasm after even minute exposures. More severe exposures can result in keratitis, iritis, corneal perforation, and blindness.
• Respiratory: Irritation of the mucous membranes may be observed on examination of the oropharynx and nose. Evidence of pulmonary edema, including rales and wheezes, may be noted on auscultation. Pulmonary thromboses are prominent features of severe CX exposure.
• Gastrointestinal: Some animal data suggest that CX may cause hemorrhagic inflammatory changes in the GI tract.