FAR INFRARED TORSIONAL AND BENDING VIBRATIONS OF TOLUENE AND ITS DERIVATIVES AND THE BARRIER HEIGHT TO INTERNAL ROTATION.

Abstract : The far infrared spectra of ortho-, meta-, and para halogenated toluene; and butadiene- and glyoxal-type molecules was investigated. Torsional vibrations were assigned and barriers to internal rotation for methyl groups and C-C single bonds in conjugated systems have been calculated. Low bending frequencies in aromatic and acyclic conjugated molecules were observed and in some cases assigned to specific vibrational motion. Results are given on the shift in frequency resulting from changes from liquid to vapor phase. Band contours in the mid infrared region for aromatic compounds were studied in an attempt to distinguish molecules with free rotation of the methyl group. A performance comparison of Golay detectors to thermocouple is also reported. (Author)