GAS-PHASE REACTIONS OF 1,4-BENZODIOXAN, 2,3-DIHYDROBENZOFURAN, AND 2,3-BENZOFURAN WITH OH RADICALS AND O3

The kinetics of the gas-phase reactions of 1,4-benzodioxan, 2,3-dihydrobenzofuran, and 2,3-benzofuran with OH radicals and O3 have been studied at 298 +/- 2 K and atmospheric pressure of air and the products have also been investigated. 1,4-Benzodioxan and 2,3-dihydrobenzofuran were chosen as volatile model compounds for dibenzo-p-dioxin and dibenzofuran, respectively. The rate constants, or upper limits thereof, for the O3 reactions were (in cm3 molecule-1 s-1 units): 1,4-benzodioxan, < 1.2 x 10(-20); 2,3-dihydrobenzofuran, < 1 x 10(-19); and 2,3-benzofuran, (1.83 +/- 0.21) x 10(-18). Using a relative rate method, the rate constants for the OH radical reactions (in cm3 molecule-1 s-1 units) were: 1,4-dibenzodioxan, (2.52 +/- 0.38) x 10(-11); 2,3-dihydrobenzofuran, (3.66 +/- 0.56) x 10(-11); and 2,3-benzofuran, (3.73 +/- 0.74) x 10(-11). Salicylaldehyde was observed as a product of the OH radical-initiated and O3 reactions of 2,3-benzofuran, with measured formation yields of 0.26 +/- 0.05 and 0.13 +/- 0.07, respectively.