Temperature and Pressure-Dependent Rate Coefficients for the Reaction of Vinyl Radical with Molecular Oxygen

State-of-the-art
calculations of the C2H3O2 potential
energy surface are presented. A new method
is described for computing the interaction potential for R + O2 reactions. The method, which combines accurate determination
of the quartet potential along the doublet minimum energy path with
multireference calculations of the doublet/quartet splitting, decreases
the uncertainty in the doublet potential and thence the rate constants
by more than a factor of 2. The temperature- and pressure-dependent
rate coefficients are computed using variable reaction coordinate
transition-state theory, variational transition-state theory, and
conventional transition-state theory, as implemented in a new RRKM/ME
code. The main bimolecular product channels are CH2O +
HCO at lower temperatures and CH2CHO + O at higher temperatures.
Above 10 atm, the collisional stabilization of CH2CHOO
directly competes with these two product channels. CH2CHOO
decomposes primarily to CH2O + HCO. The next two most significant
bimolecular products are OCHCHO + H and 3CHCHO + OH, and
not C2H2 + HO2. C2H3 + O2 will be predominantly chain branching above
1700 K. Uncertainty analysis is presented for the two most important
transition states. The uncertainties in these two barrier heights
result in a significant uncertainty in the temperature at which CH2CHO + O overtakes all other product channels.