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The alternative hydrolysis channels for triazophos are systematically investigated by performing the B3LYP/6-311++G(d,p), M06-2X/6-311++G(d,p) as well as MP2/6-311G(d) levels. Two possible mechanisms, the P–OR1 and P–OEt disintegration routes, are intensively studied; simultaneously, the concerted and stepwise neutral pathways are discussed at great length. In order to explore the effect of additional water, the hydrolysis channel in the presence of extra water is examined in detail. Moreover, the effect of solvent on water is evaluated by applying PCM model at M06-2X/6-311+G(d,p) method. Our results convincingly suggest that the stepwise processes are more favorable than the concerted ones and the most preferred mechanism seems to be the stepwise of P–OR1 rupture channel for the direct hydrolysis. The water-catalyzed hydrolysis is energetically preferred to the direct hydrolysis. Furthermore, the solvent effect has only a slight effect on the reaction mechanism. [ABSTRACT FROM AUTHOR]

The possible aminolysis pathways of carbaryl are investigated by using the B3LYP/6-311++G(d,p), M06-2X/6-311++G(d,p) and MP2/6-311++G(d,p) levels. The uncatalyzed, base-catalyzed and water-catalyzed aminolyses are explored in our calculation. For each case, three alterative channels, the concerted, addition-elimination (B2) and elimination-addition (E1cB) channel via an isocyanate, are evaluated. Our results convincingly demonstrate that the most favorable mechanism is the E1cB channel for all of the aminolysis reactions in the gas phase. For B2 and E1cB routes, the first stage is the rate-determining step. The base-catalyzed and water-catalyzed aminolysis reactions have more advantages to the uncatalyzed one. The solvent effect for acetonitrile does not notably alter the mechanism of the aminolysis. [ABSTRACT FROM AUTHOR]

The possible hydrolysis mechanisms for acetamiprid (AAP) with H3O+, H2O and OH− in the gas phase were studied by employing the B3LYP/6-311+G(d,p) and MP2/6-311+G(d,p) levels. In each case, two different pathways were taken into account in our calculations. Moreover, the solvent effect of water was estimated at the B3LYP/6-311+G(d,p) level by using the conductor-like polarizable continuum model (CPCM). The calculated results clearly showed that hydrolysis of AAP with OH− could readily take place in comparison with hydrolysis with H3O+, H2O. The most favorable pathway in the gas phase is the proton transfer toward the N atom in the single bond of AAP in the hydrolysis with OH−. The solvent effect does not significantly change the conclusion. The free energy barrier height of 25.74 kcal/mol (107.6 kJ/mol) is in excellent agreement with the available experimental value (106.3 kJ/mol). [ABSTRACT FROM AUTHOR]

The possible mechanisms of the aminolysis reaction of propylene carbonate with ammonia were investigated by computational techniques. Optimized structures for all the stationary points were examined by employing the B3LYP/6-311++G(d,p) and MP2/6-311++G(d,p) methods. The uncatalyzed, base-catalyzed and acid-catalyzed aminolysis reactions were taken into account. Two possible mechanisms of the concerted process and the addition/elimination stepwise pathway are investigated, and the first stages of the stepwise mechanism for all pathways are the rate-limiting processes. The results indicate that the concerted process of non-catalyzed aminolysis has lower energy barrier in comparison with the stepwise mechanism. Concerning the base-catalyzed and acid-catalyzed aminolysis, the neutral stepwise pathway is more favorable than the concerted mechanism and the energy barriers of all steps are lower than those of the uncatalyzed aminolysis. The solvent effect by a polarized continuum model does not significantly change the conclusion. [ABSTRACT FROM AUTHOR]

The hydrolysis process for the acephate was explored comprehensively by employing the B3LYP/6-311++G(d,p), M06-2X/6-311++G(d,p) together with MP2/6-311++G(d,p)//M06-2X/6-311++G(d,p) methods. Four possible pathways, the P-O, P-S, P-N and C-N disintegration routes including the concerted and stepwise mechanisms, are studied in detail. The hydrolysis channels are intensively investigated in the presence of an additional H2O to examine the effect of extra H2O. Our results convincingly demonstrate that the stepwise pathways are preferable to the concerted ones for all processes and that the P-S cleavage channels with remarkably lower energy barriers are more favorable than other pathways. The water-assisted hydrolysis proceeds through lower energy barrier comparing with the direct one. Furthermore, all reactions in the gas phase are more easier to take place than those in the solution. [ABSTRACT FROM AUTHOR]