Theoretical Investigation on Reaction Mechanism and Kinetics of M-xylene Bicyclic Peroxy Radical with HO2
M-xylene bicyclic peroxy radical(M-BPR)is an important atmospheric intermediate formed by the oxida-tion of m-xylene,which plays an im-portant role in the new particle for-mation and growth of secondary or-ganic aerosol.In this work,the reac-tion mechanism,thermodynamic analysis,and kinetics of the reaction between M-BPR and HO2 were in-vestigated at the CCSD(T)/cc-pVDZ//B3LYP/6-311G(d,p)level of theory coupled with transition state theory.The calcu-lated results indicate that the title reaction can occur on both singlet and triplet potential en-ergy surfaces,and the formation of hydroperoxides and 3O2 via triplet state is the main reac-tion channel,while the other four singlet product channels are negligible due to the higher barrier heights.Additionally,the reaction rate constants are estimated by using the transi-tion state theory over the temperature range of 258 K to 378 K,and reaction rate constants are found to be negatively correlated with temperature.At 298 K,the total rate constant for the title reaction is 1.86×10-11 cm3·molecule-1·s-1.The calculated rate constants over the studied temperature range were used to fit the data and the three-parameter Arrhenius ex-pression is obtained to be k(T)=4.22 × 10-15.(T/300)1.44·exp(2505/T).
M-xyleneHO2 radicalBicyclic peroxy radicalReaction mechanismTransi-tion state theory
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