INGRARED SPECTRA INVESTIGATION OF PARA-SUBTITUTED BENZENE COMPOUNDS

摘要

As the final step in making vibrational assignments of the low-frequency vibrations of benzene compounds, complete vibrational assignments of several representative compounds were made.nComplete vibrational assignments were made for a monosubstituted benzene with an electron-donating substituent (phenol) and one with an electron-attracting substituent (benzonitrile). In order to confirm the assignments and to obtain more information on the modes of vibration, ring-deuterated aromatics, phenol and benzonitrile, were pre¬pared and assigned.nThe effects of disubstitution were studied by making an assignment of p-cresol and several of its deuterated derivatives such as p-cresol-OD and p-cresol-d4.nBy use of the results of these assignments and those available in the literature, frequency assignments in the CsBr spectral region (650-300 cm) were made from the spectra of 279 benzene derivatives. These assignments include several benzene-like ring deformations and some vibrations that are either internal vibrations of the substit¬uent group or involve the ring-substituent bond. The assigned frequencies show that group frequencies (or rather group perturbations) exist for benzene derivatives in the low-frequency region.nSome data have been obtained on the low-frequency (300-50 cm-*) infrared spectra of phenol and p-cresol. From these data, assignments can be tentatively made for the O-H- • • O stretching and bending vibrations.