Phosgene oxime
Encyclopedia
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 yellowish liquids. It has a strong, disagreeable odor and a violently irritating vapor.
:
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 base hydrolysis:
Similar processes provide an easy way to destroy this dangerous compound. Hydrazine converts it to HCN and N2.
. 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.
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
Cl2CNOH. It is a potent chemical weapon, specifically a nettle agent
Nettle agent
A nettle agent or urticant is a variety of chemical warfare agent that produces corrosive skin and tissue injury upon contact, resulting in erythema, urticaria, intense itching and a hive-like rash....
. 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.
Preparation and reactions
Phosgene oxime is generally prepared by reduction of chloropicrinChloropicrin
Chloropicrin, also known as PS, is a chemical compound with the structural formula Cl3CNO2. This colourless highly toxic liquid was once used in chemical warfare and is currently used as a fumigant and nematocide.-History:...
:
- 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
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. 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 erythemaErythemaErythema is redness of the skin, caused by hyperemia of the capillaries in the lower layers of the skin. It occurs with any skin injury, infection, or inflammation...
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 escharEscharAn eschar 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, necrotizing spider bite wounds, and exposure to cutaneous anthrax....
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 conjunctivitisConjunctivitisConjunctivitis refers to inflammation of the conjunctiva...
, lacrimation, lid edema, and blepharospasmBlepharospasmA blepharospasm , is any abnormal contraction or twitch of the eyelid....
after even minute exposures. More severe exposures can result in keratitisKeratitisKeratitis is a condition in which the eye's cornea, the front part of the eye, becomes inflamed. The condition is often marked by moderate to intense pain and usually involves impaired eyesight.-Types:...
, iritisIritisIritis is a form of anterior uveitis and refers to the inflammation of the iris of the eye.-Types:There are two main types of iritis: acute and chronic. They differ in numerous ways....
, corneal perforation, and blindnessBlindnessBlindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define 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 auscultationAuscultationAuscultation is the term for listening to the internal sounds of the body, usually using a stethoscope...
. Pulmonary thrombosesPulmonary embolismPulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
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 waterWater
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
. 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.