Electronic Spectra of Polynitrophenols and their Anions

Abstract

The absorption spectra of p-nitrophenol, 2, 4-dinitrophenol, picric acid and their anions, all in water, were measured in the presence or absence of either hydrochloric acid or sodium hydroxide. The long wavelength absorption maxima of these polynitrophenols shift toward blue in the order of p-nitrophenol, 2, 4-dinitrophenol and picric acid, with increasing molar absorbancy indexes in the same order. The absorption maxima of the anions similarly shift toward blue. The absorption maxima of each anion lie at longer wavelengths than do those of the corresponding polynitrophenol. These red shifts are greater with the increasing number of the nitro group. The high-intensity bands of these nitro compounds containing two or three electron-attracting substituents are interpreted from the viewpoint of Nagakura and Tanaka’s theory of the intramolecular charge transfer spectra.