Kinetics of Hydrogen Abstraction and Addition Reactions of 3-Hexene by OH Radical

摘要

Rate coefficients of H-atom abstraction and addition reactions of 3-hexene by the hydroxyl radical (OH) were determined using canonical variational transition-state theory, with potential energy surface evaluated at the CCSD/CBS//BHandHLYP/6-311G (d, p) level and quantum mechanical effect corrected by the multi-dimensional small-curvature tunneling method. Results reveal that accounting for approximate 70% of the overall H-atom abstractions occur in the allylic site via both direct and indirect channels. The indirect channel containing two Van der Waals pre-reactive complexes exhibits two times higher rate coefficient relative to the direct one. The OH-addition reaction also contains two Van der Waals complexes, and its submerged barrier results in a negative temperature coefficient behavior at low temperatures. In contrast, the OH-addition pathway dominates only at the temperatures below 590 K whereas the H-atom abstraction reactions dominate overwhelmingly at the temperature over 590 K. All of the rate coefficients calculated with an uncertainty of a factor of 5 were estimated. Analyses on the potential energy surface and minimum reaction path were also performed in this study.