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

The excited triplet state of 1-nitronaphthalene ( 3 1NN*) reacts with OH − with a second-order reaction rate constant of (1.66 ± 0.08)×10 7 M −1 s −1 (μ ± σ). The reaction yields the &z.rad;OH radical and the radical anion 1NN − &z.rad;. In aerated solution, the radical 1NN − &z.rad; would react with O 2 to finally produce H 2 O 2 upon hydroperoxide/superoxide disproportionation. The photolysis of H 2 O 2 is another potential source of &z.rad;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 H 2 O by 3 1NN*, with rate constant 3.8 ± 0.3 M −1 s −1 , could be the main &z.rad;OH source at pH 6.5. The formation of &z.rad;OH by irradiated 1-nitronaphthalene (1NN) is accounted for by oxidation of OH − and possibly of H 2 O by the 1NN triplet state.