Bioremediation of halogenated xenobiotic compounds by microorganisms is an important mechanism for the removal of polychlorinated biphenyls (PCBs) and other halogenated pollutants from industrial and agricultural sources.  A principal pathway for this detoxification of halogenated aromatic compounds is nucleophilic conjugation of glutathione catalyzed by glutathione-S-transferases.  In order to elucidate the fundamental mechanism of these reactions and factors responsible for reactivity, we have studied reactions of planar and non-coplanar PCB congeners with thiomethoxide, a strong nucleophile and model for glutathione.  Molecular orbital theory was applied at Hartree-Fock and Density Functional Theory levels of theory to the reaction hypersurface in the gas phase and in aqueous solution using the SM8 method of Cramer and Truhlar.  Comparison was made to the nucleophilic reactions of simple chlorobenzenes, which appear to be single-step processes in the gas phase with no sigma-complex or Meisenheimer complex as a true intermediate on the reaction coordinate.

Theoretical modeling of nucleophilic aromatic substitution by glutathione in polychlorinated biphenyls (PCBs)

243rd National Meeting (2012)

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