Atmospheric and indoor chemistry of gas-phase indole, quinoline, and isoquinoline

The gas-phase chemistry of the nitrogen-containing organic compounds indole, quinoline and isoquinoline, which are present in environmental tobacco smoke, has been investigated. No photolysis of these nitrogen heterocycles was observed under indoor “white” fluorescent lighting conditions. Rate constants for the gas-phase reactions of these compounds with OH radicals, NO3 radicals, NO2, and O3 were measured, and the rate constants obtained (in cm3 molecule−1s−1 units) were: for reaction with the OH radical: indole, (1.54 ± 0.35) × 10−10; quinoline, (1.16 ± 0.55) × 10−11; isoquinoline, (8.5 ± 3.6) × 10−12; for reaction with the NO3 radical: indole, (1.3 ± 0.5) × 10−10; for reaction with NO2: indole,< 2 × 10−19; quinoline, < 1.6 × 10−20; isoquinoline,< 1.1 × 10 and for reaction with O3: indole, (4.9 ± 1.8) × 10−17; quinoline, < 1.0 × 10−19; and isoquinoline, < 1.1 × 10−19. Evidence was obtained that quinoline reacts with gas-phase nitric acid and this is also expected to be the case for isoquinoline. These data indicate that in indoor environments, quinoline and isoquinoline will be largely removed by air exchange unless gas-phase nitric acid is present, while indole will be removed by chemical reaction if NO3 radicals are present at part-per-trillion levels. Products of the O3 and OH radical reactions with indole have been studied and the possible O3 reaction mechanism is discussed.