Mechanism and kinetics of the oxidation of propargyl radical by atomic oxygen

Automated reaction path discovery tools have been used to map out the C₃H₃O potential energy surface and determine the prevailing channels for oxidation of the propargyl radical with atomic oxygen. The energy of the stationary points was then evaluated at the CCSD(T)/CBS//ωB97X-D/6-311+G(d,p) level of electronic structure theory. The C₃H₃ + O total and individual product channel rate constants were evaluated with Rice-Ramsperger-Kassel-Marcus Master Equation calculations combined with variable reaction coordinate transition state theory assessment of barrierless entrance channels. The total reaction rate so determined is in quantitative agreement with experiments, highlighting the relevance of accounting for C₃H₃ + O recombination on the excited electronic state surface. C₂HCHO (propynal) + H are predicted as the prevailing reaction products, followed by CH₂CCO (propadienone) + H, with minor contributions from C₂H₂ + HCO and C₂H₃ + CO. The calculated rate constants have been utilized in kinetic simulations, which tested the impact of the C₃H₃ + O reaction on chemical reactivity in premixed laminar flames of acetylene, ethylene, allene, propyne, and benzene. The results displayed macroscopic changes of the model predictions at low pressures (< 0.1 atm) and rich conditions, a reduction in the consumption of propargyl via C₃H₃ + O, and a substantial decrease in the C₂H₂ + HCO reactivity to C₂H₃ + CO. The updated model showed an improved performance in predicting C₂ species in the considered flames.