Conformational studies on parathion

Abstract

AbstractTheoretical conformational studies have been carried out at the density functional theory (DFT) level on parathion (O,O‐diethyl‐O‐p‐nitrophenyl phosphorothioate), to correlate the conformational properties of this molecule with its biological activity. Different conformers of parathion have been taken into account, and the accuracy of our theoretical approach has been gauged against the results of the second‐order Møller–Plesset perturbation calculations. The aqueous solvation of these molecules has been studied at the DFT level, using a polarized continuum model (PCM) with a conductor‐like screening reaction field approach. The results show that parathion has high conformational flexibility in the gas phase, as well as in an aqueous medium, and the barriers to transition to different low‐energy conformers are thermally allowed. The molecular electrostatic potential surfaces of the various low‐energy conformers of this molecule have been compared with the related non‐aged enzyme‐bound organophosphorus structure to investigate the role of the calculated conformers on the biological activity of this molecule. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006