ASSIGNMENTS OF CARBON-SULFUR VIBRATIONS BY SELENATION - AN FT-IR AND FT-RAMAN STUDY ON 1,3,5,-TRITHIACYCLOHEXANE

The IR and Raman spectra of 1,3,5-trithiaeyclohexane (1) and 1,3,5-tri selenocyclohexane (2) have been recorded with FT-instrumentation withi n 3500-100 cm(-1), and the C-S vibrations of 1 have been reviewed by c omparing its spectra with those of 2. The IR and Raman spectra slightl y differ from those previously reported and some vibrations, previousl y assigned to C-H modes in 1 on the basis of NCT calculations, are rea ssigned to C-S modes on the basis of the selenation effect. ''Selenati on'' has proved to be a very simple and effective tool in recognizing carbon-sulfur vibrations both in IR and Raman. The Raman peaks due to carbon-chalcogen vibrations are less intense in 1 than in 2, according to the higher polarizability of the selenium atom.