Raman Scattering Intensities of the NO2 Symmetric Stretching Vibration Band of Some Aromatic Nitrocompounds

Raman scattering intensities of the NO₂ symmetric stretching vibration band were measured for some aromatic nitrocompounds. It was shown that in the case of ortho alkyl-substituted nitrobenzenes, the intensities decrease in an orderly fashion with the increase of the degrees of twisting of NO₂ group from the plane of benzene ring. From this result, it was assumed that the factor determining the intensities in question is the conjugation effect between NO₂ group and benzene ring. Then, the intensities for some para substituted nitrobenzenes were examined, and the influence of substituents was discussed in terms of the conjugation effect. It was shown that when the electron donating character of substituents becomes stronger, the intensities intensity change among the compounds. The more experimental data and the detailed theoretical analysis of them are necessary not only for the elucidation of spectroscopic aspects of the intensity in question, but also for establishing the criterion for the application of it to the group type analysis and the microanalysis. Therefore, further experimental and theoretical examinations are required and now proceeding in our laboratory.