RAMAN, INFRARED AND ELECTRONIC ABSORPTION-SPECTRA OF SOME TRISUBSTITUTED BENZENES

The Raman and infrared spectra of 1-bromo-2,4-, 1-bromo-3,4- and 1-bromo-3,5-difluorobenzenes and 1,3-dichloro-4-fluorobenzene were recorded, respectively, on a Cary-Model laser Raman spectrophotometer using an Ar+ laser with three Czerny-Littrow monochromators and a Perkin-Elmer Model 377 infrared spectrophotometer. The electronic absorption spectra of all these molecules and also that of 1,3-dichloro-2-fluorobenzene in the ultraviolet region in vapour phase have been recorded on a medium and Hilger large quartz spectrograph and also on a Hitachi Model U-3200 UV/VIS spectrophotometer. All the molecules exhibit two pi* <-- pi band systems corresponding to B1(2u) <-- A1(1g) (lambda-2600 angstrom) and B1(1u) <-- A1(1g) (lambda-2100 angstrom) systems of benzene. The assignment of frequencies to various modes of vibration has been proposed.