(389e) Toward Detailed Chemical Mechanisms for the Efficient Destruction of Novichok Neurotoxins

Novichoks are dangerous neurotoxins that must be destroyed safely if deployed, possibly by incineration. They were invented by Soviet chemists near the end of the Cold War, are known to have been used outside Russia only in the past seven years (Sergei Skripal and others in the UK, 2018; Alexei Navalny, 2020), and their chemical structures have only recently been declassified. This project aims to develop a detailed chemical reaction mechanism for the incineration of three Novichoks, codenamed A-230, A-232, and A-234, using computational chemistry and avoiding any exposure through experiments. Specific goals are to: 1) ensure the complete destruction of toxic compounds, 2) identify intermediate species that might form during the process, 3) optimize temperature and conditions for safe and effective disposal, and 4) understand side reactions that could lead to hazardous byproducts.

Initial research is to create skeletal mechanisms for the three target compounds, proposing possible reactions that can occur in combustion and pyrolysis inside an incinerator. The compounds have a -P(F)(=O)- central group in common, bonded on one side to an imide -N=C(CH₃)N(C₂H₅)₂ and on the other to -CH₃, -OCH₃, or -OCH₂CH₃. Such structures should be subject to radical abstraction of Hs, pericyclic decompositions or isomerizations, and homolytic bond scissions; the resulting radicals can beta-scission, combine, add to π bonds, or abstract Hs.

Determination of bond dissociation energies ∆H°₂₉₈(AB→A•+B•) helps determine the most likely places for H abstractions and bond scissions. Initial calculations are with Gaussian 16 at the B3LYP/6-31G(d,p) level, which typically gives excellent structures and internal frequencies despite the large number of electrons. Ideal-gas thermochemistry will be reported at this level and higher levels of theory for the entire molecule, smaller model compounds, and their fragments. Reaction kinetics will be computed and tested for dominant pathways with Chemkin reactor simulations.