Raman-band contour analysis in the liquid systems nitromethane + benzene and nitromethane + carbon tetrachloride

Abstract

Characteristics of reorientational motion and vibrational relaxation in pure nitromethane and nitromethane + benzene and nitromethane + carbon tetrachloride mixtures have been obtained from anisotropic and isotropic Raman bandwidth analyses of the 655 cm^–1 band of nitromethane and the 992 cm^–1 band of benzene. The results indicate that in pure liquid nitromethane the vibrational relaxation of the 655 cm^–1 Raman mode appears to be dominated by permanent dipole moment interactions among neighbouring molecules. Molecular rotation with angular jumps involving an activation energy of ca. 7.9 kJ mol^–1 appears to be the dominant mechanism for the reorientational process. In nitromethane + benzene solutions vibrational and reorientational results are consistent with the presence of electrical intermolecular interactions between benzene and nitromethane, with significant changes in the derived polarizability tensor of the benzene ring-breathing mode. In nitromethane + carbon tetrachloride solutions the Raman vibrational and reorientational results are consistent with intramolecular association of nitromethane.