Formation of ring-retaining products from the OH radical-initated reactions of o-, m-, and p-xylene

The ring-retaining products formed from the OH radical-initiated reactions of o-, m-, and p-xylene in the presence of NO_x have been identified and their formation yields determined. Experiments were carried out at 298 ± 2 K and in the presence of 740 torr total pressure of air. The products observed, and their yields, were: from o-xylene, o-tolualdehyde, 0.0453; 2-methylbenzyl nitrate, (0.0135 + 5.5 × 10^?17 NO₂]); 2,3-dimethylphenol, 0.097; 3,4-dimethyl-phenol, 0.064; 3-nitro-o-xylene, 0.0059; 4-nitro-o-xylene, (0.0111 + 9.9 × 10^?17 NO₂]); from m-xylene, m-tolualdehyde, 0.0331; 3-methylbenzyl nitrate, 0.0061; 2,4-dimethylphenol, 0.099; 2,6-dimethylphenol, 0.111; 4-nitro-m-xylene, 0.0018; 5-nitro-m-xylene, (0.0032 + 1.6 × 10^?17 NO₂]); from p-xylene, p-tolualdehyde, 0.0701; 4-methylbenzyl nitrate, 0.0082; 2,5-dimethylphenol, 0.188, 2-nitro-p-xylene, (0.0120 + 2.8 × 10^?17 NO₂]), where the NO₂ concentration is in molecule cm^?3 units. The nitro-xylene data are consistent with our recent product study of the corresponding reactions of benzene and toluene and indicate that under the experimental conditions employed the dimethylhydroxycyclohexadienyl radicals reacted with NO₂ and not with O₂. When combined with literature ring-cleavage product yields, these data show that ca. 55–80% of the reaction pathways are accounted for.