A Theoretical and Computational Analysis of the Methyl-Vinyl + O₂ Reaction and Its Effects on Propene Combustion

A detailed analysis of the reaction of CH₃CCH₂ and CH₃CHCH with molecular oxygen is presented. The C₃H₅O₂ potential energy surface was characterized using a combination of electronic structure methods. The majority of the stationary points on the PES was determined at the CCSD(T)-F12a/cc-pVTZ-F12//B2PLYPD3/cc-pVTZ level of theory, with the remaining transition states computed using multireference methods. Microcanonical rate theory and the master equation are used to determine the temperature- and pressure-dependent rate coefficients for each reaction channel. The main product channels are CH₂O + CH₃CO for CH₃CCH₂ and CH3CHO + CHO for CH₃CHCH. The rate constants for these two reactions at 1 atm are k = 9.03 × 10²² × T^-3.21 × exp^-2162/T and 1.50 × 10¹⁹ × T^-2.10 × exp^-1260/T cm^-3 mol^-1 s^-1, respectively. In contrast to C₂H₃ + O₂, the methyl-vinyl + O₂ reactions remain chain propagating, even at high temperatures. The new rate coefficients were implemented in a detailed mechanism taken from the literature. These changes have a modest effect on the ignition delay time and laminar flame speeds for propene combustion.