Sarin
From Wikipedia, the free encyclopedia
| Sarin[1] | |
|---|---|
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| IUPAC name | 2-(Fluoro-methylphosphoryl)oxypropane |
| Other names | O-isopropyl methylphosphonofluoridate GB |
| Identifiers | |
| CAS number | 107-44-8 |
| PubChem | |
| SMILES |
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| InChI |
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| Properties | |
| Molecular formula | C4H10FO2P |
| Molar mass | 140.09 g/mol |
| Appearance | Clear colorless liquid. Odorless in pure form. |
| Density | 1.0887 g/cm³ at 25 °C 1.102 g/cm³ at 20 °C |
| Melting point |
-56 °C |
| Boiling point |
158 °C |
| Solubility in water | miscible |
| Hazards | |
| NFPA 704 |
 1
4
1
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| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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Sarin, also known by its NATO designation of GB, is an extremely toxic substance whose sole application is as a nerve agent. As a chemical weapon, it is classified as a weapon of mass destruction by the United Nations in UN Resolution 687. Production and stockpiling of sarin was outlawed by the Chemical Weapons Convention of 1993.
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[edit] Chemical characteristics
Sarin is a fluorinated phosphonate and is similar in structure and has a similar mechanism of action as some commonly used insecticides, such as malathion. It is similar in biological activity to carbamates used as insecticides such as sevin, and medicines such as pyridostigmine, neostigmine, and physostigmine.
At room temperature, sarin is a colorless, odorless liquid. Its low vapor pressure (2.9 mmHg at 25 °C) makes it relatively ineffective as a terrorist inhalation weapon. Its vapor is also colorless and odorless. It can be made more persistent through the addition of certain oils or petroleum products.
Sarin can be used as a binary chemical weapon; its two precursors are methylphosphonyl difluoride and a mixture of isopropyl alcohol and isopropylamine. The isopropylamine neutralizes the hydrogen fluoride generated during the chemical reaction.
Production of Sarin is extremely dangerous given its inherent toxicity, as well as the fact that the flouride ion is also extremely corrosive to the manufacturing equipment itself. Therefore in early synthesis and production, injurious leaks and accidents were commonplace.
[edit] Shelf life
Sarin has a relatively short shelf life, and will degrade after a period of several weeks to several months. The shelf life may be greatly shortened by impurities in precursor materials. According to the CIA,[2] in 1989 the Iraqi Government destroyed 40 or more tons of sarin that had decomposed, and that some Iraqi sarin had a shelf life of only a few weeks, owing mostly to impure precursors.
Like other nerve agents, sarin can be chemically deactivated with a strong alkali. Sodium hydroxide can be used in a hydrolysis reaction to destroy sarin, converting it to effectively harmless sodium salts.[3]
[edit] Efforts to lengthen shelf life
Nations stockpiling sarin have tried to overcome the problem of its short shelf life in three ways:
- The shelf life of unitary (pure) sarin may be lengthened by increasing the purity of the precursor and intermediate chemicals and refining the production process.
- Incorporating a stabilizer chemical called tributylamine. Later this was replaced by diisopropylcarbodiimide (DIC), which allowed for sarin to be stored in aluminum casings.
- Developing binary chemical weapons, where the two precursor chemicals are stored separately in the same shell, and mixed to form the agent immediately before or when the shell is in flight. This approach has the dual benefit of making the issue of shelf life irrelevant and greatly increasing the safety of sarin munitions. Experts, however, do not put the shelf life of this type of weapon past 5 years.
[edit] Biological effects
