Nucleophilic destruction of organophosphate toxins: A computational investigation

Abstract

Computed reaction enthalpies, free energies, and activation barriers in vacuo are presented for the nucleophilic detoxification of the organophosphorus compounds (H)(H O)P( O)F, (H)(H 3C O)P( O)F and (H 3C)(CH(CH 3) 2 O)P( O)F via the reaction R 1 OH + (R 2)(R 3 O)P( O)F → (R 2)(R 3 O)P( O)(O R 1) + H F for a wide variety of R 1 OH nucleophiles. Density functional theory at the B3LYP/6-311++G( d, p) computational level was employed for all the calculations. A multi-step Wright-type reaction mechanism [J. B. Wright, W.E. White, J. Mol. Struct. (THEOCHEM) 454 (1998) 259], which proceeds via a proton transfer from the nucleophile to the fluorine atom through the phosphinyl oxygen atom, was consistently found to have a lower activation barrier in the gas-phase than for the corresponding mechanism that operates via a proton transfer from the nucleophile directly to the fluorine atom. Of the nucleophilic agents investigated, peroxybenzoic acid and o-iodosobenzoic acid had the lowest classical activation barrier for the Wright-type mechanism.