Theoretical studies on anharmonic effect and reaction mechanism of reaction CMP+OH

The reaction rate constants between 3-chloro-2-methylpropene (CMP) and OH radical were calculated utilizing the Yao-Lin (YL) method, which concluded harmonic and anharmonic values. In this paper, the anharmonic effect and reaction mechanism of the title reaction and its subsequent reactions were supplied with a detailed analysis. In the CMP+OH reaction, there are two reaction complexes, eight intermediate complexes, nine transition states, and seven products. The optimizations and frequencies of all molecular configurations were calculated at the M06-2X/6-311++G(2d,p) level, and the single-point energies of them were more accurately calculated at the CCSD(T)/6-311++G(2d,p) level. Five main reaction pathways were determined by calculation, including two OH radical addition reactions and three hydrogen atom abstraction reactions. The obtained data show that the values of rate constant increase with the increasing calculation temperature and energy, whether they are harmonic or anharmonic. Furthermore, the kinetic parameters of the CMP+OH reaction and its subsequent reaction steps containing anharmonic effect were fitted. From a series of results, it can be seen that the anharmonic effect in this reaction cannot be simply ignored, and these results can provide theoretical reference for the related research of chemical reaction between CMP and OH radical.