Kinetics and mechanisms of the gas-phase reactions of the NO3 radical with aromatic compounds

Article abstract of DOI:10.1002/kin.550260504

The kinetics and nitrated products of the gas-phase reactions of the NO₃ radical with methoxybenzene, 1,2-, 1,3-, and 1,4-dimethoxybenzene, dibenzofuran and dibenzo-p-dioxin have been investigated at 297 ± 2 K and in the presence of one atmosphere of air. A relative rate method was used for the kinetic measurements. No reactions of methoxybenzene or dibenzofuran with the NO₃ radical were observed. The dimethoxybenzenes were observed to react by H-atom abstraction and NO₃ radical addition to the aromatic ring, while dibenzo-p-dioxin reacted by NO₃ radical addition to the aromatic rings. For these compounds, the NO₃ radical addition pathways were observed to be reversible. At the NO₂ concentrations employed, the NO₃-aromatic adducts reacted with NO₂ and the observed rate constants increased with increasing NO₂ concentration. However, for dibenzo-p-dioxin the observed rate constant became independent of the NO₂ concentration for concentrations ≥ 4.8 × 10¹³ molecule cm^-3, and under these conditions the rate constant of 6.8 × 10^-14 cm³ molecule^-1 s^-1 was taken to be that for addition of the NO₃ radical to the aromatic rings. The proposed NO₃ radical reaction mechanisms are discussed.