Formation of hydroxyl radicals by irradiated 1-nitronaphthalene (1NN): oxidation of hydroxyl ions and water by the 1NN triplet state
Résumé
The excited triplet state of 1-nitronaphthalene (31NN*) reacts with OH- with a second-order reaction rate constant of (1.66 ± 0.8)¥107 M-1 s-1 (m ± s). The reaction yields the ∑OH radical and the radical anion 1NN-∑. In aerated solution, the radical 1NN-∑ would react with O2 to finally produce H2O2 upon hydroperoxide/superoxide disproportionation. The photolysis of H2O2 is another potential source of ∑OH, but such a pathway would be a minor one in circumneutral (pH 6.5) or in basic solution ([OH-] = 0.3-0.5 M). The oxidation of H2O by 31NN*, with rate constant 3.8 ± 0.3 M-1 s-1, could be the main ∑OH source at pH 6.5.