Difference between revisions of "Phosgene oxime"

Latest revision as of 10:05, 20 September 2010

Phosgene oxime, or CX, is an organic compound with the formula Cl₂CNOH. It is a potent chemical weapon, specifically a nettle agent. The compound itself is a colorless solid, but impure samples are often a yellowish liquids. It has a strong, disagreeable odor and a violently irritating vapor.

Preparation and reactions

Phosgene oxime is generally prepared by reduction of chloropicrin:

Cl₃CNO₂ + 2 Sn + 5 HCl + H₂O → Cl₂C=N-OH + 2 H₃O[SnCl₃]

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^[2]

The compound is electrophilic and thus sensitive to nucleophiles, including base hydrolysis:

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

Similar processes provide an easy way to destroy this dangerous compound. Hydrazine converts it to HCN and N₂.

Safety

Phosgene oxime is a vesicant.^[3] 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.

Decontamination, treatment, and handling properties

Phosgene oxime is highly soluble in water. It is corrosive to metals and also decomposes on contact with metals. It is rapidly hydrolysed by alkaline solutions. Adsorbent powders such as fullers earth or talcum powder can also be used.

References

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

1. ↑ ^{1.0 1.1 1.2 1.3} ATSDR Medical Management Guidelines for Phosgene Oxime
2. ↑ Prandtl, Wilhelm; Dollfus, Werner "Über das Trichlor-nitroso-methan, das Dichlor-formoxim (Phosgen-oxim) und einige ihrer Derivate, 2. Mitteil.: Über zwei neue Derivate der Kohlensäure" Berichte der Deutschen Chemischen Gesellschaft, 1932, volume 65B, 754-9. doi:10.1002/cber.19320650515
3. ↑ McManus John; Huebner Kermit "Vesicants" Critical care clinics (2005), 21(4), 707-18. doi:10.1016/j.ccc.2005.06.005