On the effect of 2-propanol on phenol photonitration upon nitrate photolysis

It is shown that the enhancement by 2-propanol of the nitration of phenol upon nitrate photolysis is compatible with the inhibition by the alcohol of in-cage recombination between O-center dot(-) and (NO2)-N-center dot. This effect would increase the availability of (NO2)-N-center dot that is involved into phenol nitration, despite the enhancement by the alcohol of the production of superoxide that is a scavenger of (NO2)-N-center dot. A kinetic model is proposed to describe the experimental data and to get insight into the processes involved. Kinetic calculations suggest that in the absence of 2-propanol less than 25% of cage O-center dot(-) and (NO2)-N-center dot would evolve into bulk species, the remainder undergoing recombination to nitrate. If reaction between cage O-center dot(-) and phenol were not negligible, the percentage of bulk species formation would be even lower. The data also show that most of the recombination between (OH)-O-center dot/O-center dot(-) and (NO2)-N-center dot would take place in the solvent cage instead of the solution bulk. (C) 2011 Elsevier B.V. All rights reserved.