Computational Study of the Mechanism and Product Yields in the Reaction Systems C₂H₃\n+ CH₃ ⇄ C₃H₆ ⇄ H + C₃H₅ and C₂H₃ + CH₃ → CH₄ + C₂H₂

Abstract

The mechanism of the radical−radical reaction C₂H₃ + CH₃ (1) was studied by quantum chemical methods.\nThe pathways of reaction channels observed in previous experimental studies, as well as those of other potential\nchannels, were investigated. The results of the quantum chemical study and of the earlier experimental work\nwere used to create a model of the chemically activated route (C₂H₃ + CH₃ ⇄ C₃H₆<b></b>→ H + C₃H₅) of reaction\n1. In this model, energy- and angular momentum-dependent rate constants are calculated using the RRKM\nmethod in combination with the microcanonical variational selection of the transition states. Pressure effects\nare described by solution of the master equation. Temperature and pressure dependences of the rate constants\nand product yields were investigated. The model was used to predict the rate constants and branching fractions\nof reaction 1 at temperatures and pressures outside the experimental ranges. The same model was used to\nanalyze kinetics of two other reactions which occur on the same potential energy surface: the thermal\ndecomposition of propene (2) and the reaction of H atom with allyl radical, H + C₃H₅ ⇄ C₃H₆<b></b>→ C₂H₃ +\nCH₃ (3). The results demonstrate the increasing importance of the CH₃ + C₂H₃ channels in both reactions 2\nand 3 at high temperatures (above ∼1500 K).