Photochemical and photosensitised reactions involving 1-nitronaphthalene and nitrite in aqueous solutionElectronic supplementary information (ESI) available: Effects of nitrite and pH on the decay of 31NN, pH trend of 1NN transformation rate, effects of 2-propanol and oxygen on the photonitration of 1NN. See DOI: 10.1039/c0pp00311e

The excited triplet state of 1-nitronaphthalene, 1NN, (31NN) is able to oxidise nitrite to NO2, with a second-order rate constant that varies from (3.56 ± 0.11) × 108M−1s−1(μ ± σ) at pH 2.0 to (3.36 ± 0.28) × 109M−1s−1at pH 6.5. The polychromatic quantum yield of NO2photogeneration by 1NN in neutral solution is ΦNO21NN≥ (5.7 ± 1.5) × 107× [NO2−]/{(3.4 ± 0.3) × 109× [NO2−] + 6.0 × 105} in the wavelength interval of 300–440 nm. Irradiated 1NN is also able to produce OH, with a polychromatic quantum yield ΦOH1NN= (3.42 ± 0.42) × 10−4. In the presence of 1NN and NO2−/HNO2under irradiation, excited 1NN (probably its triplet state) would react with NO2to yield two dinitronaphthalene isomers, 15DNN and 18DNN. The photonitration of 1NN is maximum around pH 3.5. At higher pH the formation rate of NO2by photolysis of NO2−/HNO2would be lower, because the photolysis of nitrite is less efficient than that of HNO2. At lower pH, the reaction between 31NN and NO2is probably replaced by other processes (involving e.g.31NN-H+) that do not yield the dinitronaphthalenes. [ABSTRACT FROM AUTHOR]