The Photochemical Reduction of Nitrobenzene and Its Reduction Intermediates. X. The Photochemical Reduction of the Monosubstituted Nitrobenzenes in 2-Propanol

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Abstract
The photochemical reduction of the monosubstituted nitrobenzenes has been investigated in 2-propanol under a nitrogen atmosphere. The nitrobenzenes with electron-withdrawing groups on meta- and para-positions (p-NO2, m- and p-CN, m- and p-COOC2H5, p-COOCH(CH3)2, and m- and p-COOH) were photoreduced to the corresponding anilines, and nitrobenzene and the para-substituted nitrobenzenes with electron-donating groups (p-CH3 and p-OCH3) were photoreduced to the corresponding phenylhydroxylamines. p-Nitroaniline and p-nitrophenol were unreactive toward the photoreduction. In the experiments on the determination of the quantum yields for the nitrobenzenes’ disappearance upon irradiation with a 313- or 366-nm light, it has been found that there is a linear correlation between the log-values of the relative quantum yields of the substituted nitrobenzenes and nitrobenzene and the Hammett constants, and the ρ value was + 1.5. The results obtained suggest that the hydrogen-abstraction reaction of the photoexcited nitrobenzenes may proceed electrophilically.