Theoretical investigation of the decarboxylation reaction of CH3CO2 radical

A theoretical study on the decarboxylation reaction of CH3CO2 radical at the MP2 level of theory has been carried out. It is found that the thermal reaction CH3CO2 → CH3 + CO2 may occur on the 2A′(A′) potential energy surface of CH3CO2 via a reaction barrier of 4.2 kcal/mol at the PMP4/6-311+G(3df,3pd)//MP2/6-311+G(2df,2p) level of theory. Another possible reaction path is the CH3CO2(A′) transform into the CH3CO2(A1) and thus undergo a barrier-less dissociation into the products CH3 + CO2. The thermal rate constants of channel CH3CO2(A′) → CH3 + CO2.were evaluated based on the electronic structure and energy information from the PMP4/6-311+G(3df,3pd)//MP2/6-311+G(2df,2p) level of theory with microcanonical variational transition state theory (μVT) in the temperature range of 200-3000 K. The fitted Arrhenius expression from the forward μVT rate constants within the calculated temperature range is KμVT=2.196×1011T0.294e(-2.304×103/T)s-1. It is also found that the geometry of the CH3CO2 radical is sensitive to the basis set used.