Effect of sulfur substitution for methanolysis of paraoxon: CO vs. PO bond cleavage from density-functional theory

► We studied the methanolysis of paraoxon and the effects of sulfur substitution. ► An SN2-type mechanism is observed for the P-path and C-path. ► Except for the S:O5′ reaction the P-path is more favorable than C-path kinetically. ► Except for the S:O2′(or O2″) reaction the products of C-path are more accessible. ► The results are consistent with the previous experimental and theoretical studies.