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From sarin to "Novichoks", as well as on Skripal case. Popular scientific sketch

19.04.2018

Part 1. Organophosphorus chemical agents – from sarin to “Novichoks”

Chemical agents (CAs) of nerve action are the most dangerous group of the CAs. All the warfare CAs related to this group are organophosphorus compounds.

Compounds of the G group (sarin and others) were the first group of these organophosphorus CAs.

The “Novichoks” binary systems the information about which was published for the first time by Vil Mirzayanov in 1992 [1] became the last group. Developments were conducted in the State Scientific Research Institute of Organic Chemistry and Technology (GosNIIOKhT) [2]. Mirzayanov was not a developer of “Novichoks”, he took part in testing of these compounds.

In 1995 Mirzayanov left to the USA where he wrote and published two books which contain some information on “Novichoks”. More precisely, the first book [3] is collected articles, one of them was written by Mirzayanov, the second one [4] is a long enough Mirzayanov’s autobiography written, as I thought, for the purpose of the self-justification. In chapter 8 of this book formulas and preparation schemes of a number of organophosphorus CA, including “Novichoks”, are given.

When I began to write this popular scientific sketch in connection with Skripal poisoning (under Anatoly Baranov, Chief Editor of Forum.msk, request) I wanted to restrict it by “Novichoks” only. But later I understood that it is necessary to describe history of all the organophosphorus CAs, as there are many interesting moments in it and there are obvious relationships between the first groups of these CAs and the subsequent ones.

Thus all the organophosphorus CAs can be divided into one-component (unitary) ones which are high toxic and act directly, and two-component (binary) systems where both components are low or non-toxic, and toxic substances are formed at their mixing and interaction.

For information – “Novichoks” relate to binary systems.

 

A. One-component (unitary) organophosphorus CAs

Compounds of the G group – sarin and others

4 CAs of the G group are described in Wikipedia – sarin [5], soman [6], cyclosarin [7] and tabun [8]. They were obtained in nazi Germany and went to the USSR, the USA and Great Britain after the II World War as trophies:

    

Sarin

GB

isopropyl alcohol residue

Soman

GD

pinacolyl alcohol residue

Cyclosarin

GF

cyclohexanol residue

Tabun

GA

Molecules of sarin, soman, cyclosarin have a strong similarity and related to one chemical group of the organophosphorus CAs, as P‑F bond is responsible for activity in them. There also is one bond with hydrocarbon radical P‑R and other bond with alcohol residual P‑OR (ester group) in them. Among themselves these three molecules differ only by alcohol residuals OR (specified under the formulas, cyclosarin was not manufactured in large quantities because of relative high price of corresponding alcohol [7]).

Compounds of this type (containing one bond P‑R) are termed phosphonates (or phosphonyl compounds, in this case – phosphonyl fluorides).

Molecule of tabun strongly differs from molecules of other substances of the G group. P‑C≡N bond is responsible for activity in it, and this is the only organophosphorus CA with similar bond. Therefore assignment of tabun to the G group is conditional (historical), from the chemical point of view it is a representative of separate chemical group of the organophosphorus CAs.

 

Synthesis of sarin and its analogues

It would seem, preparation methods of sarin and its analogues should be secret. However on the above-mentioned Wikipedia pages there are not only formulas, but also schemes of synthesis of these compounds. For example, the simplest synthesis for “the most popular” sarin is an esterification reaction given on English page [5]:

 

Methylphosphonyl difluoride

Isopropyl alcohol

 

Sarin

[Scheme 1]

Other scheme given on Russian page [5]:

 

Methylphosphonyl dichloride

Isopropyl alcohol

Sodium fluoride

 

Sarin

[Scheme 2]

Chlorides (scheme 2) is easier esterified than fluorides (scheme 1), replacement of second chlorine by fluorine is carried out under action of sodium (or potassium) fluoride.

I give these schemes as I will refer to them further in this sketch.

Soman, cyclosarin and other sarin analogues, different by alcohol residuals only, may be synthesized in the same manner as sarin.

When I saw these schemes on Wikipedia pages, I had a question – when there was a first open publication on sarin synthesis – in the West, of course, because in the USSR it was impossible.

Search in references led to a conclusion that it probably was an article [9] published in 1960 in a very solid journal, Canadian Journal of Chemistry, to which all leading libraries of the world were subscribed. Now it is possible to download pdf from the site of this journal, and it is free of charge. But the paper version was accessible still in those days.

Yes, in this Canadian scientists’ article synthesis of labeled sarin (32P) was described in several variants, but from the chemical point of view all the same. And the schemes given in Wikipedia on English page [5] obviously derived from ones described in the article [9].

Additionally it is necessary to notice that later another scheme of synthesis of sarin (and its analogues) was developed in GosNIIOKhT according to Mirzayanov [4]:

 

Methylcyanophosphinyl fluoride

Isopropyl alcohol

Sarin

[Scheme 3]

This scheme is also required further in this sketch.

 

Therefore if you hear or read in mass-media that somewhere in the East (and not only in the East) any terrorists (and not only terrorists) synthesize sarin (it is the easiest) or its analogues – be not surprised. It is quite possible. As almost 60 years these schemes are known to all who can interest them.

But observance of three conditions is necessary:

1. Specialists-chemists of enough high qualification are necessary

Now such specialists can be found in the majority of the countries of the East and Latin America, but in the majority of the countries of tropical Africa – hardly.

2. Appropriately equipped laboratory is necessary

It is not a problem, but money is needed for this purpose.

3. Strict observance of safety measures is necessary

It is possible only at performance of points 1 and 2.

Otherwise the synthesizing persons with enough high degree of probability become the first victims of the CAs synthesized by them.

Incidentally, with all responsibility I can declare that bearded men can’t work in similar laboratories: beard is a collector of contaminations and not allowed to put on a gas mask. Therefore if suddenly any mass-media show the bearded men synthesizing the CAs – don’t believe.

 

Compounds of the V group – VG, VX and VR

 

Synthesis of VG, VX and their analogues

 

Compounds of the A group

 

Synthesis of compounds of the A group

 

B. Two-component organophosphorus CAs (binary systems)

Binary systems developed in the USA

 

Binary systems developed in the USSR (“Novichoks”)

 

Synthesis of cyano-precursors – main component of binary “Novichoks”

 

Some remarks

 

On possibility of synthesis of “Novichoks” in different countries

Conclusion of part 1

 

Michael Yakhkind

Cand. of Techn. (PhD), graduate of the Moscow Institute of Fine Chemical Technology, 1981,

freelancer and expert in the field of chemistry and pharmaceutics

 

Part 1 was published in Russian on 08.04.2018

Translated into English by author

 

Next parts:

Part 2. Identification of poison and identification of manufacturing site of poison are two big differences

Part 3. How could be applied “Novichok A-234” in Salisbury?

Conclusion “Who benefits?”

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