Mustard Gas

 or sulfur mustards asre a class of related cytotoxic and vesicant chemical warfare agents with the ability to form large blisters on the exposed skin and in the lungs. Pure sulfur mustards are colorless, viscous liquids at room temperature. When used in impure form, such as warfare agents, they are usually yellow-brown in color and have an odor resembling mustard plants, garlic, or horseradish, hence the name.

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The compound readily eliminates a chloride ion by intramolecular nucleophilic substitution to form a cyclic sulfonium ion. This very reactive intermediate tends to permanently alkylate the guanine nucleotide in DNA strands, which prevents cellular division and generally leads directly to programmed cell death, or, if cell death is not immediate, the damaged DNA may lead to the development of cancer. Oxidative stress would be another pathology involved in sulfur mustard toxicity. Sulfur mustard is not very soluble in water but is very soluble in fat, contributing to its rapid absorption into the skin.

Mustard gas (bis(chloroethyl) thioether) alkylating a DNA amine base. In the wider sense, compounds with the structural element BCH2CH2X, where X is any leaving group and B is a Lewis base are known as mustards. Such compounds can form cyclic "onium" ions (sulfonium, ammoniums, etc.) that are good alkylating agents. Examples are bis(2-chloroethyl)ether, the (2-haloethyl)amines (nitrogen mustards), and sulfur sesquimustard, which has two α-chloroethyl thioether groups (ClH2C-CH2-S-) connected by an ethylene (-CH2CH2-) group.[citation needed] These compounds have a similar ability to alkylate DNA, but their physical properties, e.g. melting point, vary.

Mustard gas has extremely powerful vesicant effects on its victims. In addition, it is strongly mutagenic and carcinogenic, due to its alkylating properties. It is also lipophilic. Because people exposed to mustard gas rarely suffer immediate symptoms, and mustard-contaminated areas may appear completely normal, victims can unknowingly receive high dosages. Within 24 hours of exposure to mustard agent, victims experience intense itching and skin irritation, which gradually turns into large blisters filled with yellow fluid wherever the mustard agent contacted the skin. These are chemical burns and are very debilitating. Mustard gas vapour easily penetrates clothing fabrics such as wool or cotton, so it is not only the exposed skin of victims that gets burned. If the victim's eyes were exposed then they become sore, starting with conjunctivitis, after which the eyelids swell, resulting in temporary blindness.