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− and NO2. This effect would increase the availability of NO2 that is involved into phenol nitration, despite the enhancement by the alcohol of the production of superoxide that is a scavenger of NO2. 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− and NO2 would evolve into bulk species, the remainder undergoing recombination to nitrate. If reaction between cage O− 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− and NO2 would take place in the solvent cage instead of the solution bulk.