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Soman
Properties
Molecular formula C7H16FO2P
Molar mass 182.17 g mol−1
Appearance When pure, colorless liquid with fruity odor. With impurities, amber or dark brown, with oil of camphor odor
Density 1.022 g/cm³
Melting point

-42 °C, 231 K, -44 °F

Boiling point

198 °C, 471 K, 388 °F

Solubility in water Moderate
Vapor pressure 0.40 mmHg (53 Pa)
Hazards
Main hazards Toxic
NFPA 704
NFPA 704.svg
1
4
1
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Soman, also known by its NATO designation GD (O-Pinacolyl methylphosphonofluoridate), is an extremely toxic chemical 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. Its production is strictly controlled, and stockpiling is 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 colorless liquid with a faint odor when pure. More commonly, it is a yellow to brown color and has a strong odor described as similar to 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.

The structures of the complexes of soman with acetylcholinesterase have been solved by X-ray crystallography (PDB codes: 2wfz, 2wg0, 2wg1, and 1som).

Contents

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.

Synthesis

The manufacture of Soman is very similar to the manufacture of Sarin. The difference is that the isopropanol from the Sarin processes is replaced with pinacolyl alcohol:

MeP(O)Cl2 + MeP(O)F2 + (CH3)3 CCH(CH3)OH → MePO(F)OCH(CH3)C(CH3)3 + HCl

References

See also








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