Kinetic Analysis for Reaction of Cyclopentadiene with Hydroperoxyl Radical under Low- and Medium-Temperature...

The kinetic data of cyclopentadiene C₅H₆ oxidation reactions are significant for the construction of aromatics oxidation mechanism because cyclopentadiene C₅H₆ has been proved to be an important intermediate in the aromatics combustion. Kinetics for the elementary reactions on the potential energy surface (PES) relevant for the C₅H₆ + HO₂ reaction are studied in this work. Stationary points on the PES are calculated by employing the CCSD(T)/cc-pVTZ//B3LYP/6-311G(d,p) level of theory. High-pressure limit and pressure-dependent rate constants for elementary reactions on this PES are calculated using conventional transition state theory (TST), variational transition-state theory (VTST) and Rice-Ramsberger-Kassel-Marcus/master equation (RRKM/ME) theory. In this work, the reaction channels for the C₅H₆ + HO₂ reaction_, which include H-abstraction channels from C₅H₆ by HO₂ to form the C₅H₅ + H₂O₂ and the addition channels through well-skipping pathways to form the bimolecular products C₅H₇ + O₂ or C₅H₆O + OH, or through C₅H₇O₂ stabilization and its unimolecular decomposition to form the bimolecular products C₅H₇ + O₂ or C₅H₆O + OH, namely sequential pathways, are studied. Also, the consuming reaction channels for the compounds C₅H₆O and C₅H₇ in the addition products are studied. The dominant reaction channels for these reactions are unraveled through comparing the energy barriers and rate constants of all elementary reactions and it is found: (1) HO₂ addition to cyclopentadiene C₅H₆ is more important than direct H-abstraction. (2) in the HO₂ addition channels, the well-skipping pathways and sequential pathways are competing and the well-skipping pathways will be favor in the higher pressures and the sequential pathways will be favor in the higher temperature. (3) The major consumption reaction channel for the five-member-ring compound C₅H₆O is the reaction channel to form C₄H₆ + CO and the major consumption reaction channel for the five-member-ring compound C₅H₇ is the reaction channel to form C₃H₅ + C₂H₂. High-pressure limit rate constants and pressure-dependent rate constants for elementary reactions on the PES are calculated, which will be useful in modeling the oxidation of aromatic compounds at low- and medium-temperatures.