Gas-phase atmospheric chemistry of 1- and 2-nitronaphthalene and 1,4-naphthoquinone

Abstract

The gas-phase photolysis of 1- and 2-nitronaphthalene and the reactions of these nitroarenes with OH and NO 3 radicals, N 2O 5 and O 3 have been investigated at 298±2 K and 1 atm total pressure of air. Since 1,4-naphthoquinone was observed as a photolysis product of 1-nitronaphthalene in air, its photolysis and reactions with OH and NO 3 radicals, N 2O 5 and O 3 were also studied. Using relative rate methods for the determination of rate constants for the reactions with OH radicals and NO 3 radicals and/or N 2O 5, and rate constants of k(OH+cyclohexane) = 7.49 × 10 −12cm 3molecule −1 s −1 and k( NO 3 + propene) = 9.4 × 10 15 cm 3 molecule −1s −1 and the equilibrium constant for the NO 3 + NO 2 ahN 2 O 5 reactions of K = 2.3 × 10 −11 cm 3molecule −1, the rate constants obtained for these reactions were (in cm 3molecule −1s −1 units): for reaction with the OH radical; 1-nitronaphthalene, (5.4±1.8)× 10 −12; 2-nitronaphthalene, (5.6±0.9)× 10 −12; 1,4-naphthoquinone, (3.1±1.2) × 10 −12; for reaction with the NO 3 radical; 1-nitronaphthalene, ≤7.2× 10 −15; 2-nitronaphthalene, ≤7.2×10 −15; 1,4-naphthoquinone, <1 × 10 −15; for reaction with N 2O 5; 1-nitronaphthalene, (1.3±0.7) × 10 −18; 2-nitronaphthalene, (1.2±0.5) ×10 −18; 1,4-naphthoquinone, <4×10 −19; for reaction with O 3; 1-nitronaphthalene, include the uncertainties in the rate constants for the reference reactions or in the eq <6×10 −19; 2-nitronaphthalene, <6×10 −19; 1,4-naphthoquinone, <2×10 −19 (where the cited error limits do notuilibrium constant K). The photolysis reactions were investigated under blacklamp irradiation and under natural solar irradiation. With solar irradiation at an NO 2 photolysis rate of J NO 2 = 4.3 × 10 −3s −1, the outdoor photolysis rates were (in s −1 units): 1-nitronaphthalene, (1.37±0.10) × 10 −4; 2-nitronaphthalene, (1.06±0.08)× 10 −41,4-naphthoquinone, ~ 9 × 10 −5. These data show that under atmospheric conditions the dominant loss process of 1- and 2-nitronaphthalene and 1,4-naphthoquinone is photolysis, with calculated photolysis lifetimes of ~2 h for all three compounds. The OH radical reactions are calculated to be an order of magnitude less important than photolysis as an atmospheric loss process, with the N 2O 5, NO 3 radical and O 3 reactions being of negligible importance.