VG (

IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...

name: ''O'',''O''-diethyl ''S''- -(diethylamino)ethylphosphorothioate) (also called amiton or Tetram) is a "V-series"

nerve agent Nerve agents, sometimes also called nerve gases, are a class of organic chemistry, organic chemicals that disrupt the mechanisms by which nerves transfer messages to organs. The disruption is caused by the blocking of acetylcholinesterase (ACh ...

chemically similar to the better-known VX nerve agent. Tetram was the proposed

trade name A trade name, trading name, or business name is a pseudonym used by companies that do not operate under their registered company name. The term for this type of alternative name is fictitious business name. Registering the fictitious name with ...

for the substance and amiton its

ISO The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. Me ...

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often con ...

when it was tested as an

acaricide Acaricides are pesticides that kill members of the arachnid subclass '' Acari'', which includes ticks and mites. Acaricides are used both in medicine and agriculture, although the desired selective toxicity differs between the two fields. Termi ...

by ICI in the 1950s. It is now only of historic interest as the first member of the V-series.

History

By the 1950s, the use of

organophosphate insecticides In organic chemistry, organophosphates (also known as phosphate esters, or OPEs) are a class of organophosphorus compounds with the general structure , a central phosphate molecule with alkyl or Aryl, aromatic substituents. They can be conside ...

was well established, despite their known toxicity to mammals. For example,

parathion Parathion, also called parathion-ethyl or diethyl parathion, is an organophosphate insecticide and acaricide. It was originally developed by IG Farben in the 1940s. It is highly toxic to non-target organisms, including humans, so its use has been ...

had been developed in the 1940s and became widely used in agriculture despite its known oral toxicity. Many chemical companies continued to research this type of

acetylcholinesterase inhibitor Acetylcholinesterase inhibitors (AChEIs) also often called cholinesterase inhibitors, inhibit the enzyme acetylcholinesterase from breaking down the neurotransmitter acetylcholine into choline and acetate, thereby increasing both the level an ...

, seeking to develop alternatives which had greater human safety while retaining their activity on pests. In 1952, Dr. Ranajit Ghosh, a chemist at

Imperial Chemical Industries Imperial Chemical Industries (ICI) was a British Chemical industry, chemical company. It was, for much of its history, the largest manufacturer in Britain. Its headquarters were at Millbank in London. ICI was listed on the London Stock Exchange ...

(ICI), investigated

organophosphate In organic chemistry, organophosphates (also known as phosphate esters, or OPEs) are a class of organophosphorus compounds with the general structure , a central phosphate molecule with alkyl or aromatic substituents. They can be considered ...

esters In chemistry, an ester is a chemical compound, compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds c ...

of substituted amino ethanethiols and compared their properties to parathion, which ICI was already marketing as Fosferno. Amiton was found to be much less toxic than parathion to many insects but was considerably more toxic to acarid pests such as the spider-mite '' Tetranychus telarius''. Field trials demonstrated its utility against the red mite '' Panonychus ulmi'': a single treatment of 20 ppm was shown to give season-long control. This led to plans to market the compound under the

Tetram 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. It had been intended to formulate it as its hydrogen oxalate () salt, to minimise any hazard from the vapour. The

British Government His Majesty's Government, abbreviated to HM Government or otherwise UK Government, is the central government, central executive authority of the United Kingdom of Great Britain and Northern Ireland.

was aware of the extreme toxicity of organophosphate compounds and some of the ICI materials were sent to Porton Down, Britain’s

chemical weapons A chemical weapon (CW) is a specialized munition that uses chemicals formulated to inflict death or harm on humans. According to the Organisation for the Prohibition of Chemical Weapons (OPCW), this can be any chemical compound intended as ...

research facility, for evaluation. This led to the identification of a new class of nerve agents, later named V (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 of VX—a chemically similar but far more toxic compound—in 1961. Amiton was no longer pursued for chemical warfare or as a pesticide.

Synthesis

Amiton was first made at ICI by direct treatment of the sodium

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

of 2-diethylaminoethanethiol with diethyl phosphorochloridate: 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: Surprisingly, amiton is also the product of reacting diethylethanolamine with diethyl phosphorochloridothionate, where the initially-formed thionate ester rearranges under the conditions of the reaction:

Regulation

VG is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S.

Emergency Planning and Community Right-to-Know Act The Emergency Planning and Community Right-to-Know Act of 1986 is a United States federal law passed by the 99th United States Congress located at Title 42, Chapter 116 of the U.S. Code, concerned with emergency response preparedness. On Octobe ...

(42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities. The

Chemical Weapons Convention The Chemical Weapons Convention (CWC), officially the Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction, is an arms control treaty administered by the Organisation for ...

(CWC) classifies amiton as a Schedule 2 chemical. These are subject to fewer restrictions than Schedule 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.

References

{{DEFAULTSORT:Vg (Nerve Agent) Diethylamino compounds Acetylcholinesterase inhibitors V-series nerve agents Organothiophosphate esters Ethyl esters