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. T ...

with the formula Cl₂CNOH. It is a potent

chemical weapon A chemical weapon (CW) is a specialized munition that uses chemicals formulated to inflict death or harm on humans. According to the Organisation for the Prohibition of Chemical Weapons (OPCW), this can be any chemical compound intended as a ...

, specifically a

nettle agent Nettle agents (named after stinging nettles) or urticants are a variety of chemical warfare agents that produce corrosive skin and tissue injury upon contact, resulting in erythema, urticaria, intense itching, and a hive-like rash. Most nettle ...

. 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 Chloropicrin, also known as PS and nitrochloroform, is a chemical compound currently used as a broad-spectrum antimicrobial, fungicide, herbicide, insecticide, and nematicide. It was used as a poison gas in World War I. Its chemical structural f ...

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 Trichloronitrosomethane is a chlorinated nitrosoalkane. It is a deep blue liquid with powerful lachrymatory effects. Synthesis Trichloronitrosomethane can be produced with following methods: * Oxidation of trichloromethylsulfinic acid with nitri ...

(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 isoxazoles. 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 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 subs ...

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

erythema Erythema (from the Greek , meaning red) is redness of the skin or mucous membranes, caused by hyperemia (increased blood flow) in superficial capillaries. It occurs with any skin injury, infection, or inflammation. Examples of erythema not asso ...

tous 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 An eschar (; Greek: ''ἐσχάρᾱ'', ''eskhara''; Latin: ''eschara'') is a slough or piece of dead tissue that is cast off from the surface of the skin, particularly after a burn injury, but also seen in gangrene, ulcer, fungal infections, ...

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 Conjunctivitis, also known as pink eye, is inflammation of the 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 occur. The ...

lacrimation Tears are a clear liquid secreted by the lacrimal glands (tear gland) found in the eyes of all land mammals. Tears are made up of water, electrolytes, proteins, lipids, and mucins that form layers on the surface of eyes. The different types of ...

, lid edema, and blepharospasm 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 Uveitis () is inflammation of the uvea, the pigmented layer of the eye between the inner retina and the outer fibrous layer composed of the sclera and cornea. The uvea consists of the middle layer of pigmented vascular structures of the eye and ...

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 powe ...

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 A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

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.

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