soman

Soman (or "GD") is a synthetic (human-made) compound that affects the functioning of nerves. As such, Soman is one of a group of chemicals that are known as nerve agents.

Soman was developed in Germany in 1944. Its original purpose was as an insecticide. The chemical, which does not occur naturally in the environment, is similar to the group of insect poisons (pesticides) called organophosphates, both in activity and in how they are applied (i.e., airborne release). However, Soman (and nerve agents in general) are much more potent and deadly than the insect nerve poisons.

Several properties of Soman are responsible for its potency. It is normally a clear, colorless, and tasteless liquid, and so is not easily detected. While it typically has a slight odor reminiscent of rotting fruit, this smell can be disguised upon mixing with water or food. Even wetting the skin with soman-contaminated water can be lethal, as the poison is absorbed through the skin. In addition, Soman can vaporize when heated, and retains its toxicity when inhaled. The vapor can even cling to clothing and affect others as is it released from the clothing.

The effects of Soman begin almost immediately upon exposure. Within minutes to hours the nerves that control the functioning of muscles are inhibited from turning off the stimuli that trigger muscle activity. At the molecular level, this occurs via the inactivation of an enzyme that breaks apart another chemical that acts as a bridge between adjacent nerve cells, and so allows a nerve impulse to flow. Because the bridging chemical remains intact, nerve impulses cannot be controlled or turned off. As a result of the constant activity, muscles such as the lungs tire and can cease to function. Some of the symptoms associated with Soman exposure include watery and painful eyes, coughing, rapid breathing, diarrhea, confusion, headache, slow or fast heart rate, and, in severe cases, unconsciousness, convulsions, and respiratory failure.

These effects occur for only a short time after Soman vapor is released into the atmosphere, since it is a very volatile compound. When incorporated into water or food, however, Soman can remain active and deadly for a longer time.

The damage due to Soman is cumulative. Because the chemical can persist in the body, repeated exposure increases the concentration of Soman in the body. People in low-lying areas and valleys can be especially susceptible, as Soman is more dense than air and so "settles out" near the bottom of depressions.

Soman was one of the nerve agents that may have been used against the people of Iran by the government of Iraq under Suddam Hussein during the Iran-Iraq war in the 1980s. Soman once also once produced as a chemical weapon by the United States. Production by the United States ceased decades ago.

Further Reading

Books

Government of the United States. 21st Century Complete Guide to Chemical Weapons and Chemical Terrorism—U.S. Demilitarization Program, Stockpile Destruction Emergency Plans, Nerve Gas and Blister Agent Civilian Treatement and First Aid, Home Sheltering Plans. Washington, DC: Progressive Management, 2002.

Electronic

Agency for Toxic Substances and Disease Registry. "Nerve Agents (GA, GB, GD, VX)." Division of Toxicology, Centers for Disease Control and Prevention. March 13, 2003. <http://www.atsdr.cdc.gov/tfactsd4.html> (April 10, 2003).

Agency for Toxic Substances and Disease Registry. "Facts about Soman." Division of Toxicology, Centers for Disease Control and Prevention. March 12, 2003. <http://www.bt.cdc.gov/agent/soman/basics/facts.asp>(April 10,2003).

For other uses, see Soman (disambiguation).

Soman
IUPAC name	2-(Fluoro-methyl-phosphoryl)oxy-3,3-dimethyl-butane
Other names	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
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	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.

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). 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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