Formation of hydroxyl radicals by irradiated 1-nitronaphthalene (1NN): oxidation of hydroxyl ions and water by the 1NN triplet state

摘要

The excited triplet state of 1-nitronaphthalene (31NN*) reacts with OH− with a second-order reaction rate constant of (1.66 ± 0.08)×107 M−1 s−1 (μ ± σ). 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.