A-234 is an

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 ...

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 ...

. It was developed in the

Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

under the FOLIANT program and is one of the group of compounds referred to as

Novichok agent Novichok () is a family of nerve agents, some of which are binary chemical weapons. The agents were developed at the GosNIIOKhT state chemical research institute by the Soviet Union and Russia between 1971 and 1993. Some Novichok agents are ...

s that were revealed by

Vil Mirzayanov Vil Sultanovich Mirzayanov (, ; born 9 March 1935 in Starokangyshevo, Dyurtyulinsky District, Bashkortostan) is a Russian chemist of ethnic Tatar origin who now lives in the United States, best known for revealing secret chemical weapons experi ...

. In March 2018, the Russian ambassador to the UK, Alexander Yakovenko, claimed to have been informed by British authorities that A-234 had been identified as the agent used in the

poisoning of Sergei and Yulia Skripal The poisoning of Sergei and Yulia Skripal, also known as the Salisbury poisoning, was a botched assassination attempt to poison Sergei Skripal, a former Russian military officer and double agent for the British intelligence agencies in the cit ...

. Vladimir Uglev, one of the inventors of the Novichok series of compounds, said he was "99 percent sure that it was A-234" in relation to the

2018 Amesbury poisonings Eighteen or 18 may refer to: * 18 (number) * One of the years 18 BC, AD 18, 1918, 2018 Film, television and entertainment * ''18'' (film), a 1993 Taiwanese experimental film based on the short story ''God's Dice'' * ''Eighteen'' (film), a 2 ...

, noting its unusually high persistence in the environment. According to a classified report by the

United States Army The United States Army (USA) is the primary Land warfare, land service branch of the United States Department of Defense. It is designated as the Army of the United States in the United States Constitution.Article II, section 2, clause 1 of th ...

National Ground Intelligence Center The National Ground Intelligence Center (NGIC) is part of the United States Army Intelligence and Security Command. The NGIC provides scientific and technical intelligence (S&T) and general military intelligence (GMI) on foreign ground forces ...

, the agent designated as

A-232 A-232 is an organophosphate nerve agent. It was developed in the Soviet Union under the FOLIANT program and is one of the group of compounds referred to as Novichok agents that were revealed by Vil Mirzayanov. A-232 is reportedly slightly less pot ...

and its ethyl analog A-234, developed under the FOLIANT program, were "as toxic as VX, as resistant to treatment as

soman Soman (or GD, EA 1210, Zoman, PFMP, A-255, 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 inhibit ...

, and more difficult to detect and easier to manufacture than VX". No certain data on toxicity exist but it is estimated that the median lethal concentration of A-234 is 7 mg/m³. This means that half of 70 kg individuals under slight physical activitybreathing 15 litres of air per minutewould die within two minutes of exposure. This equates to a median lethal dose of 0.2 mg via respiration.

Regulated chemical under the Chemical Weapons Convention

As of 7 June 2020, A-234 has been added to Schedule 1 of the Annex on Chemicals of 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 ...

and it has been explicitly named as an example compound for schedule 1.A.14. For chemicals listed in Schedule 1, the most stringent declaration and verification measures are in place combined with far-reaching limits and bans on production and use. It is notable to say that Annex 1 does not explicitly relate this structure to the name A-234, instead adding this particular structure to the prohibited compounds section.

Alternative structure

An alternative structure for A-234 and the related Novichok agents had previously been proposed by Western chemical weapons experts such as Steven Hoenig and D. Hank Ellison. These structures were supported by Soviet literature of the time and were tested as

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 ...

s, however Mirzayanov explained that a number of weaker agents developed as part of the Foliant program were published in the open literature as organophosphate

pesticide Pesticides are substances that are used to control pests. They include herbicides, insecticides, nematicides, fungicides, and many others (see table). The most common of these are herbicides, which account for approximately 50% of all p ...

s, in order to disguise the secret nerve agent program as legitimate pesticide research. However, the presence of a carbonimidic chloride fluoride group and a dimethylchloroethyl group suggest that this molecule is a member of the C-series of organophosphate agents (C01), with additional mustard and (chlorofluoro-)phosgene oxime radicals, added to produce skin and lung toxicity as well as

blistering A blister is a small pocket of fluid in the upper layer of the skin caused by heat, electricity, chemicals, light, radiation, or friction Blister(s) or Blistering may also refer to: * Blood blister * Bleb (medicine) * Anti-torpedo bulge, also know ...

effects.

References

{{Neurotoxins Acetylcholinesterase inhibitors Amidines Phosphorofluoridates Novichok agents Ethyl esters

Regulated chemical under the Chemical Weapons Convention

Alternative structure

See also

References