Phosgene oxime, or CX, is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...

Cl₂CNOH. It is a potent chemical weapon, specifically a nettle agent. The compound itself is a colorless solid, but impure samples are often yellowish liquids. It has a strong, disagreeable odor and a violently irritating vapor. It is seldom used but is a precursor of compounds with fungicidal, biocidal and pesticide activity.

Preparation and reactions

Phosgene oxime can be prepared by reduction of chloropicrin using a combination of

tin Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...

metal and

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...

as the source of the active hydrogen reducing acent: : 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. The compound is electrophilic and thus sensitive to nucleophiles, including bases: : Phosgene oxime has been used to prepare heterocycles that contain N-O bonds, such as

isoxazole Isoxazole is an electron-rich azole with an oxygen atom next to the nitrogen. It is also the class of compounds containing this ring. Isoxazolyl is the univalent radical derived from isoxazole. Occurrence Isoxazole rings are found in some natural ...

s. Dehydrohalogenation upon contact with mercuric oxide generates cyanoformyl chloride, a reactive nitrile oxide: :Cl₂CNOH → ClCNO + HCl

Toxicity

Phosgene oxime is readily destroyed and detoxified upon treatment with base. Hydrazine converts it to HCN and N₂. Phosgene oxime is classified as a

vesicant A blister agent (or vesicant), is a chemical compound that causes severe skin, eye and mucosal pain and irritation. They are named for their ability to cause severe chemical burns, resulting in painful water blisters on the bodies of those affec ...

even though it does not produce blisters. It is

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ...

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 Wheal may refer to: * Wheals, a type of skin lesion * Brad Wheal (born 1996), British cricketer * Donald James Wheal (1931–2008), British British television writer, novelist and non-fiction writer * David John Wheal, Australian businessman * "Th ...

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 Mustard gas or sulfur mustard is a chemical compound belonging to a family of cytotoxic and blister agents known as mustard agents. The name ''mustard gas'' is technically incorrect: the substance, when dispersed, is often not actually a gas, b ...

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 Conjunctivitis, also known as pink eye, is inflammation of the conjunctiva, outermost layer of the white part of the eye and the inner surface of the eyelid. It makes the eye appear pink or reddish. Pain, burning, scratchiness, or itchiness may ...

, lacrimation, lid edema, and

blepharospasm Blepharospasm is any abnormal contraction of the orbicularis oculi muscle. The condition should be distinguished from the more common, and milder, involuntary quivering of an eyelid, known as myokymia, or fasciculation. In most cases, blepharosp ...

after even minute exposures. More severe exposures can result in

keratitis Keratitis is a condition in which the eye's cornea, the clear dome on the front surface of the eye, becomes inflamed. The condition is often marked by moderate to intense pain and usually involves any of the following symptoms: pain, impaired e ...

, iritis,

corneal The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...

perforation, and

blindness Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment� ...

. *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 Auscultation (based on the Latin verb ''auscultare'' "to listen") is listening to the internal sounds of the body, usually using a stethoscope. Auscultation is performed for the purposes of examining the circulatory and respiratory systems (hea ...

. 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.

References

External links

EMedicine: Urticants, Phosgene Oxime

Center for the Study of Bioterrorism: Phosgene Oxime

Centers for Disease Control: Facts About Phosgene Oxime

{{DEFAULTSORT:Phosgene Oxime Chemical weapons Organochlorides Oximes