Computational study on the mechanism and kinetics for the reaction between HO₂ and n-propyl peroxy radical

The n-propyl peroxy radical (n-C₃H₇O₂) is the key intermediate during atmospheric oxidation of propane (C₃H₈) which plays an important role in the carbon and nitrogen cycles in the troposphere. In this paper, a comprehensive theoretical study on the reaction mechanism and kinetics of the reaction between HO₂ and n-C₃H₇O₂ was performed at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-311G(d,p) level of theory. Computational results show that the HO₂ + n-C₃H₇O₂ reaction proceeds on both singlet and triplet potential energy surfaces (PESs). From an energetic point of view, the formation of C₃H₇O₂H and ³O₂ via triplet hydrogen abstraction is the most favorable channel while other product channels are negligible. In addition, the calculated rate constants for the title reaction over the temperature range of 238-398 K were calculated by the multiconformer transition state theory (MC-TST), and the calculated rate constants show a negative temperature dependence. The contributions of the other four reaction channels to the total rate constant are negligible.