Theoretical study on the reaction mechanism of chlordimeform with OH radicals.

A theoretical investigation on the multiple-channel degradation mechanism of chlordimeform with OH radicals in the atmosphere was completed using a dual-level direct dynamics method. The equilibrium geometries and the corresponding harmonic vibrational frequencies of the stationary points were obtained at the M06-2X/6-311++G(d,p) level. The minimum energy paths (MEP) were calculated at the same level, and energetic information was further refined at M06-2X/6-311++G(3df,2p) level. The rate constants for the 15 reaction channels were calculated by improved canonical variational transition state theory with small-curvature tunneling correction over the temperature range 200-1,000 K. The total rate constants are in good agreement with the available experimental data and the three-parameter expression k(T) =2.62 × 10(-18)  T (2.71) exp (899.61/T) cm(3)molecule(-1) s(-1) was given. The calculated results indicate that the addition reaction of the carbon-nitrogen double bond is the major channel, while the abstraction reaction from the benzene ring of chlordimeform is the least competitive channel.