On the formation of benzene oxide/oxepin in the gas-phase reaction of OH radicals with benzene

Product formation in the gas-phase reaction of OH radicals with benzene was studied under flow-tube conditions at 13 and 100 mbar at 298 K in O2/He mixtures using direct MS, on-line FT-IR spectroscopy and GC-MS/FID detection. Benzene was used in a large excess, preventing consecutive reactions of products. Under all experimental conditions investigated there was no clear indication for a formation pathway for benzene oxide/oxepin; the observed yield was <0.03 (FT-IR) and <0.01 (GC-MS). Observed products were CO: 0.30±0.13, phenol: 0.23±0.07, formic acid: 0.13±0.05, p-benzoquinone: 0.055±0.009, and unidentified carbonyls: 0.59±0.11 (yields at 100 mbar).