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

Abstract

Crossed molecular beam experiments were performed to elucidate the chemical dynamics of the para-tolyl (CH3C6H4) radical reaction with molecular oxygen (O-2) at an average collision energy of 35.3 +/- 1.4 kJ mol(-1). Combined with theoretical calculations, the results show that paratolyl 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.