Aminolysis and hydrolysis of an organophosphorus pesticide: A theoretical insight into the reaction mechanism for thio methyl parathion

Abstract A systematic investigation of the aminolysis and hydrolysis mechanisms for organophosphorus pesticides was performed by using the B3LYP/6–311++G(d,p), M06-2X/6–311++G(d,p) and MP2/6-311G(d,p) methods. Three plausible reaction routes, the P O, P S, P O R disintegration channels involving the concerted and stepwise stages, are theoretically assessed. In addition, the solvent effects for the acetonitrile are also taken into account at the M06-2X/6–311++G(d,p) level. The computational outcomes suggest that the values of M06-2X level are quite close to those of MP2 and the three dissociation mechanisms are parallel. Compared with the hydrolysis which is readily to occur for the stepwise process, the aminolysis for the concerted mechanism is more easier to take place in the gas phase. What is more, all routes in the gas phase are more easier to occur than those in the solution. Our findings will offer valuable information for the degradation of organophosphorus pesticides.