Abstract
The kinetics and nitrated products of the gasโphase reactions of the NO~3~ radical with methoxybenzene, 1,2โ, 1,3โ, and 1,4โdimethoxybenzene, dibenzofuran and dibenzoโpโdioxin have been investigated at 297 ยฑ 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 NO~3~ radical were observed. The dimethoxybenzenes were observed to react by Hโatom abstraction and NO~3~ radical addition to the aromatic ring, while dibenzoโpโdioxin reacted by NO~3~ radical addition to the aromatic rings. For these compounds, the NO~3~ radical addition pathways were observed to be reversible. At the NO~2~ concentrations employed, the NO~3~โaromatic adducts reacted with NO~2~ and the observed rate constants increased with increasing NO~2~ concentration. However, for dibenzoโpโdioxin the observed rate constant became independent of the NO~2~ concentration for concentrations โฅ 4.8 ร 10^13^ molecule cm^โ3^, and under these conditions the rate constant of 6.8 ร 10^โ14^ cm^3^ molecule^โ1^ s^โ1^ was taken to be that for addition of the NO~3~ radical to the aromatic rings. The proposed NO~3~ radical reaction mechanisms are discussed. ยฉ 1994 John Wiley & Sons, Inc.