Phosgene oxime
IUPAC name	dichloroformaldoxime
Other names	dichloroformoxime, CX
Identifiers
CAS number	1794-86-1
Properties
Molar mass	113.93 g mol−1
Appearance	colorless crystalline solid or yellowish-brown liquid[1]
Melting point	35-40 °C[1]
Boiling point	128 °C[1]
Solubility in water	70%[1]
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Phosgene oxime, also known as dichloroformoxime or CX, is a chemical weapon, specifically an urticant (nettle agent). It was first produced in 1929. As a solid, it is colorless; as a liquid, it is yellow-brown. It has a strong, disagreeable odor and a violently irritating vapor. The chemical formula for phosgene oxime is CCl₂NOH.^[2]

This chemical has no industrial applications, so accidental exposure is extremely unlikely to occur. Therefore, any exposure to CX is almost certainly the result of its deliberate use as a chemical warfare agent.

[edit] Preparation

Phosgene oxime can be prepared by reduction of chloropicrin with tin (iron results in lower yields) in diethyl ether-concentrated hydrochloric acid mixture. Transient violet coloration of the reaction mixture suggests intermediate formation of trichloronitrosomethane, which is then further reduced to phosgene oxime:

Cl₃C-NO₂ + Sn + 3 HCl → Cl₃C-NO + H[SnCl₃] + H₂O

Cl₃C-NO + Sn + 2 HCl → Cl₂C=N-OH + H[SnCl₃]

[edit] Symptoms of phosgene oxime poisoning

Phosgene oxime is toxic if inhaled, ingested, or absorbed by the skin and the effects of the poisoning occur almost immediately. If inhaled, it irritates the airway and may eventually lead to pulmonary edema. The effects on the skin include wheals, hives, itching, and necrosis of the skin, which scabs and falls off. Absorption through the skin can also lead to pulmonary edema. It also causes lacrimation in the eyes and even blindness.

The 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.

The greatest risk from CX is that it may be used synergistically with another chemical warfare agent i.e. nerve gas.^{[citation needed]}

[edit] Decontamination and treatment

There is no antidote for phosgene oxime poisoning. Generally, any treatment is supportive. However, because CX is rapidly hydrolysed by alkaline solutions, an alkaline liquid (e.g. sodium bicarbonate or calcium carbonate dissolved in water) can be used for decontamination purposes. Adsorbent powders such as fullers earth or talcum powder can also be used.

In an emergency, if no CX-specific treatment is available, water can be used to irrigate the victims' eyes and to gently wash their skin. Naturally, if shower facilities are readily available then these can also be used.

[edit] Chemical properties

Phosgene oxime is around 70% soluble in water. The boiling point is 128 °C (262 °F), its melting point is between 35–40 °C (95–104 °F). Its vapor density is greater than air, which mean it tends to settle in low lying areas. It is corrosive to metals and also decomposes on contact with metals.

[edit] References

[edit] External links

• EMedicine: Urticants, Phosgene Oxime
• Center for the Study of Bioterrorism: Phosgene Oxime
• Centers for Disease Control: Facts About Phosgene Oxime
• Virtual Naval Hospital: Phosgene Oxime