Gas-Phase Reactions of Phenyl Radicals with Aromatic Molecules

Article abstract of DOI:10.1021/j100328a026

Relative rates of reactions of phenyl radicals with a series of aromatic and polycyclic aromatic compounds are reported.Most studies were done in static reactors at 450 deg C using diphenyl diketone (benzil) as the phenyl radical source.Reactions with the following molecules are reported: benzene, toluene, p-xylene, 1,3,5-trimethylbenzene, phenol, bromobenzene, naphthalene, biphenyl, anthracene, 9-methylanthracene, and triphenylene.For reactions with substituted benzenes, H abstraction is the dominant reaction.Relative rates of phenylation at different sites do not closely follow established trends for rates of radical attack.It is proposed that these deviations are primarily due to a dependence of the degree of reversibility on the specific site of phenylation.These studies also show that the rates of phenyl and H-atom migration around the ring in adduct radicals are slow relative to dissociation.Also, by use of these results to link literature rate data from high and low temperatures, a rate expression for H abstraction from p-xylene by phenyl of 10^9.6 exp(-4.4 kcal/RT) M^-1 s^-1 is derived.