Soman
| |||
| Names | |||
|---|---|---|---|
| Preferred IUPAC name
3,3-Dimethylbutan-2-yl methylphosphonofluoridate | |||
| Other names
GD; Phosphonofluoridic acid, methyl-, 1, 2, 2-trimethylpropyl ester; 2-(Fluoromethylphosphoryl)oxy-3,3-dimethylbutane; 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
| |||
| Identifiers | |||
3D model (JSmol)
|
|||
| ChEMBL | |||
| ChemSpider | |||
PubChem CID
|
|||
CompTox Dashboard (EPA)
|
|||
| |||
| |||
| Properties | |||
| C7H16FO2P | |||
| Molar mass | 182.175 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 (−44 °F; 231 K) | ||
| Boiling point | 198 °C (388 °F; 471 K) | ||
| Moderate | |||
| Vapor pressure | 0.40 mmHg (53 Pa) | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards
|
Toxic | ||
| NFPA 704 (fire diamond) | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |||
Soman, or GD (systematic name: 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 where it is classified as a Schedule 1 substance. 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.
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 crystal structure of soman complexed with acetylcholinesterase was determined by Millard et al. (1999) by X-ray crystallography (PDB codes: 2wfz, 2wg0, 2wg1, and 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
Protective Measures
Langston and Myers tested the influence of diet on soman toxicity in rats. For this purpose, rats were fed four different diets: standard (SD), choline-enriched (CH), glucose-enriched (GL) and a ketogenic diet (KD). The doses used in this study were 0.4-0.5 of the acute 24-h LD50.
30% of the GL group died after the third administration of soman (0.4 LD50) and the remaining 70% died after the fourth administration of 0.5 LD50. At this cumulative dose (352ug/kg), only 10% of the SD group died, while all of the rats fed a KD and CH survived. When the cumulative dose was greater than 400ug/kg, both SD and CH groups had an approximate terminal survival value of 55%. In contrast, only one animal in the KD group died after the final soman administration (cumulative dose of 627ug/kg). 90% of KD-fed rats survived.
"Specifically, all KD animals survived a cumulative 5.0 LD50 dose of soman, whereas all glucose animals died following a cumulative 3.2 LD50 dose of soman. Not only was survival enhanced in KD animals, but there were also minimal differences in body weights compared to dietary controls injected with saline. Furthermore, KD animals exposed to soman exhibited few performance decrements on an avoidance task, and there were fewer instances of behavioral incapacitation in KD animals compared to the other diet groups."
References
- United States Senate, 103d Congress, 2d Session. (May 25, 1994). Material Safety Data Sheet -- Lethal Nerve Agents Somain (GD and Thickened GD). Retrieved Nov. 6, 2004.
- Millard CB, Kryger G, Ordentlich A; et al. (1999). "Crystal structures of aged phosphonylated acetylcholinesterase: nerve agent reaction products at the atomic level". Biochemistry. 38 (22): 7032–9. doi:10.1021/bi982678l. PMID 10353814.
{{cite journal}}: Explicit use of et al. in:|author=(help); Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - J.L. Langston, T.M. Myers: Diet composition modifies the toxicity of repeated soman exposure in rats. Neurotoxicology, Mai, 27 2011