Computational study of the alcoholysis for organophosphorus pesticides: The reaction of phoxim with methanol

Abstract

The alcoholysis process for one of organophosphorus pesticides, phoxim, was systematically examined by using the M06-2X/6–311++G(d,p) and MP2/6–311++G(d,p)//M06-2X/6–311++G(d,p) levels. Two possible alcoholysis mechanisms, P–OR1, P–OEt rupture channels together with the concerted and stepwise steps, were theoretically evaluated. The catalytic role of an extra methanol was also simulated. Furthermore, the influence of solvent on water was also taken into consideration for the M06-2X/6–311++G(d,p) level of theory. Our predicted results show convincingly that the P–OEt disintegration pathway is slightly more favorable than the P–OR removal channel. The stepwise pathway is calculated to be more prominent than the concerted one for all reactions. It can be observed that the methanol-assisted alcoholysis is more easier to take place than the direct alcoholysis. Solvent effect does not have remarkable effect on the reaction mechanism.