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| Names | |
|---|---|
| Preferred IUPAC name S-[2-(Diethylamino)ethyl]O,O-diethyl phosphorothioate | |
| Identifiers | |
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3D model (JSmol) | |
| ChemSpider |
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| UNII | |
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| Properties | |
| C10H24NO3PS | |
| Molar mass | 269.34 g·mol−1 |
| Boiling point | 85.5 °C (185.9 °F; 358.6 K) at 0.05 mmHg[1] |
| Vapor pressure | 0.01 mmHg at 80 °C |
| Hazards | |
| NFPA 704 (fire diamond) | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
VG (IUPAC name:O,O-diethylS-[2-(diethylamino)ethyl] phosphorothioate) (also calledamiton orTetram) is a "V-series"nerve agent chemically similar to the better-knownVX nerve agent. Tetram was the proposedtrade name for the substance and amiton itsISOcommon name when it was tested as anacaricide byICI in the 1950s. It is now only of historic interest as the first member of the V-series.
By the 1950s, the use oforganophosphate insecticides was well established, despite their known toxicity to mammals.[2] For example,parathion had been developed in the 1940s and became widely used in agriculture despite its known oral toxicity.[3] Many chemical companies continued to research this type ofacetylcholinesterase inhibitor, seeking to develop alternatives which had greater human safety while retaining their activity on pests. In 1952, Dr. Ranajit Ghosh, a chemist atImperial Chemical Industries (ICI), investigatedorganophosphateesters of substituted aminoethanethiols and compared their properties to parathion, which ICI was already marketing as Fosferno.[4][5]
Amiton was found to be much less toxic than parathion to many insects but was considerably more toxic toacarid pests such as the spider-miteTetranychus telarius.Field trials demonstrated its utility against the red mitePanonychus ulmi: a single treatment of 20 ppm was shown to give season-long control. This led to plans to market the compound under thetrade nameTetram but the oral LD50 of 5 mg/kg to rats meant that the compound was comparable to parathion in mammalian toxicity while having a more limited use, so its development was halted as not being commercially viable.[4] It had been intended toformulate it as itshydrogen oxalate (HC2O−4) salt, to minimise any hazard from the vapour.[6]
TheBritish Government was aware of the extreme toxicity of organophosphate compounds and some of the ICI materials were sent toPorton Down,Britain’schemical weapons research facility, for evaluation. This led to the identification of a new class ofnerve agents, later namedV (venomous) agents. Britain officially renounced chemical and biological weapons in 1956, but the United States continued research into this class, leading to the mass production ofVX—a chemically similar but far more toxic compound—in 1961. Amiton was no longer pursued for chemical warfare or as a pesticide.[4][7][8]
Amiton was first made at ICI by direct treatment of the sodiumsalt of 2-diethylaminoethanethiol withdiethyl phosphorochloridate:[1]
(CH3CH2)2NCH2CH2S− Na+ + ClP(=O)(OCH2CH2)2 → amiton + NaCl
It was characterised as its hydrogen oxalate salt, with melting point 98–99°C. Alternative methods tried included the reaction between 2-diethylaminoethyl chloride and sodium diethyl phosphorothioate:
(CH3CH2)2NCH2CH2Cl + Na+−SP(=O)(OCH2CH2)2 → amiton + NaCl
Surprisingly, amiton is also the product of reactingdiethylethanolamine with diethyl phosphorochloridothionate, where the initially-formed thionate ester(CH3CH2)2NCH2CH2OP(=S)(OCH2CH2)2 rearranges under the conditions of the reaction:[1]
(CH3CH2)2NCH2CH2O− Na+ + ClP(=S)(OCH2CH2)2 → amiton + NaCl
VG is classified as anextremely hazardous substance in the United States as defined in Section 302 of the U.S.Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.[9]
TheChemical Weapons Convention (CWC) classifies amiton as aSchedule 2 chemical.[10] These are subject to fewer restrictions thanSchedule 1 chemicals but are still highly regulated. CWC member states are required to submit annual reports detailing the amounts they synthesize, process, consume, import, or export. Any trade involving these chemicals must specify the recipient country: exports to non-CWC member states are prohibited. These regulations ensure strict monitoring and prevent misuse while allowing legitimate industrial and research applications.[11][7]
