Oxidation of the para-Tolyl Radical by Molecular Oxygen under Single-Collison Conditions: Formation of the para-Toloxy Radical

J Phys Chem Lett. 2016 Dec 15;7(24):5121-5127. doi: 10.1021/acs.jpclett.6b02357. Epub 2016 Dec 1.


Crossed molecular beam experiments were performed to elucidate the chemical dynamics of the para-tolyl (CH3C6H4) radical reaction with molecular oxygen (O2) at an average collision energy of 35.3 ± 1.4 kJ mol-1. Combined with theoretical calculations, the results show that para-tolyl is efficiently oxidized by molecular oxygen to para-toloxy (CH3C6H4O) plus ground-state atomic oxygen via a complex forming, overall exoergic reaction (experimental, -33 ± 16 kJ mol-1; computational, -42 ± 8 kJ mol-1). The reaction dynamics are analogous to those observed for the phenyl (C6H5) plus molecular oxygen system which suggests the methyl group is a spectator during para-tolyl oxidation and that application of phenyl thermochemistry and reaction rates to para-substituted aryls is likely a suitable approximation.