posted on 2021-04-30, 20:31authored byAlexander
N. Morozov, Iakov A. Medvedkov, Valeriy N. Azyazov, Alexander M. Mebel
Quantum chemical calculations of
the C6H5O2 potential energy surface
(PES) were carried out to
study the mechanism of the phenoxy + O(3P) and phenyl +
O2 reactions. CASPT2(15e,13o)/CBS//CASSCF(15e,13o)/DZP
multireference calculations were utilized to map out the minimum energy
path for the entrance channels of the phenoxy + O(3P) reaction.
Stationary points on the C6H5O2 PES
were explored at the CCSD(T)-F12/cc-pVTZ-f12//B3LYP/6–311++G**
level for the species with a single-reference character of the wave
function and at the CASPT2(15e,13o)/CBS//B3LYP/6–311++G** level
of theory for the species with a multireference character of the wave
function. Conventional, variational, and variable reaction coordinate
transition-state theories were employed in Rice–Ramsperger–Kassel–Marcus
master equation calculations to assess temperature- and pressure-dependent
phenomenological rate constants and product branching ratios. The
main bimolecular product channels of the phenoxy + O(3P)
reaction are concluded to be para/ortho-benzoquinone
+ H, 2,4-cyclopentadienone + HCO and, at high temperatures, also phenyl
+ O2. The main bimolecular product channels of the phenyl
+ O2 reaction include 2,4-cyclopentadienone + HCO at lower
temperatures and phenoxy + O(3P) at higher temperatures.
For both the phenoxy + O(3P) and phenyl + O2 reactions, the collisional stabilization of peroxybenzene at low
temperatures and high pressures competes with the bimolecular product
channels.