Soman

Soman, also known by its NATO designation GD (O-Pinacolyl methylphosphonofluoridate) is an extremely toxic substance. It is a nerve agent, interfering with normal functioning of the mammalian nervous system by inhibiting the cholinesterase enzyme. As a chemical weapon, it is classified as a weapon of mass destruction by the United Nations according to UN Resolution 687, and its production is strictly controlled and stockpiling outlawed by the Chemical Weapons Convention of 1993. Soman was the third of the so-called "G-series" nerve agents to be discovered (along with GA (tabun), GB (sarin), and GF (cyclosarin)).

It is a volatile, corrosive and colourless liquid with a faint odour when pure. More commonly, it is a yellow to brown color and has a stronger odour described as camphor. The LCt₅₀ for Soman is 70 mg·min/m³ in humans. It is both more lethal and more persistent than sarin or tabun, but less so than cyclosarin.

GD can be thickened for use as a chemical spray using an acryloid copolymer. It can also be deployed as a binary chemical weapon; its precursor chemicals are methylphosphonyl difluoride and a mixture of pinacolyl alcohol and an amine.

Alternative names

Soman is occasionally referred to by names other than "soman" or "GD":
* Phosphonofluoridic acid, methyl-, 1, 2, 2-trimethylpropyl ester
* Pinacolyl methylphosphonofluoridate
* 1,2,2-Trimethylpropyl methylphosphonofluoridate
* Methylpinacolyloxyfluorophosphine oxide
* Pinacolyloxymethylphosphonyl fluoride
* Pinacolyl methanefluorophosphonate
* Methylfluoropinacolylphosphonate
* Fluoromethylpinacolyloxyphosphine Oxide
* Methylpinacolyloxyphosphonyl fluoride
* Pinacolyl methylfluorophosphonate
* 1,2,2-Trimethylpropoxyfluoromethylphosphine oxide

History

Soman was discovered by Richard Kuhn in Germany in 1944, and represented the last wartime nerve agent discovery (GF was not found until 1949). Soman was given the identifier GD post-war (GC was already in medical use) when the information relating to soman was recovered by the Soviet Union from its hiding place in a mine. The 3D crystal structure of soman complexed with acetylcholinesterase was determined by Millard et al (1999) and can be seen at Proteopedia|1som.

References

* United States Senate, 103d Congress, 2d Session. (May 25, 1994). [http://www.gulfweb.org/bigdoc/report/appgd.html Material Safety Data Sheet -- Lethal Nerve Agents Somain (GD and Thickened GD)] . Retrieved Nov. 6, 2004.
* Millard CB, Kryger G, Ordentlich A, Greenblatt HM, Harel M, Raves ML, Segall Y, Barak D, Shafferman A, Silman I, Sussman JL "Crystal structures of aged phosphonylated acetylcholinesterase: nerve agent reaction products at the atomic level", "Biochemistry" (1999) 38, 7032-9. PMID 10353814

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