The effect of intermolecular interactions on the isotope structures of the Raman bands of CHCl3, CCl3F and CCl3CN

Abstract

The Raman spectra of chloroform, trichloromethyl fluoride and trichloromethyl cyanide have been studied as pure liquids and as solutions in various solvents. In particular the isotope patterns of those a ₁ modes which involve mainly chlorine vibrations have been studied as a function of concentration in cyclopentane. In certain bands of the pure liquids where the isotope structure is well resolved this structure is not consistent with species containing three equivalent chlorine atoms. Pure CFCl₃ possesses bands which exhibit both this anomalous pattern and the expected pattern. On dilution in a wide range of solvents the anomalous bands revert to the expected pattern and the normal bands are unaffected. The anomalous patterns observed and the behaviours on dilution were identical for all three compounds. This evidence has been interpreted on the basis of association in the pure liquids though the specific nature of the interactions involved depends on the compound.