13. Theoretical Investigation of the NO₃ Initiated Reaction of VOCs

We have studied the reaction mechanism for the NO₃ radical initiated atmospheric oxidation of three cresol isomers, p-cresol, m-cresol and o-cresol, in the presence of NO₂. We have focused on the reaction mechanism leading to the ring retaining products, methyl-nitrophenol isomers and methyl-benzoquinone isomers. Geometries of the reactants, intermediates, transition states, and products have been optimized at the DFT-B3LYP level of theory with the 6-311 + G(d,p) basis set. The single point energy calculations have been carried out at the CCSD(T) level of theory with the cc-pVDZ basis set. The reaction path where the NO₃ and NO₂ radicals are added ipso and ortho to the OH group of the cresol isomer, respectively, has the lowest energy barrier.