Vibrational spectroscopic studies of the phase transition behavior in solid cyclohexene

Abstract

The vibrational spectra (FT-ir and Raman) of cyclohexene have been examined as functions of temperature. The phase transition behavior is complex and highly dependent upon the thermal treatment of the sample. Spectra of the stable low temperature form (phase II) are quite different from those of the other phases, and suggest that the crystal has either Ci or C2h symmetry with two molecules per primitive unit cell. The asymmetric line shapes of the internal vibrational bands and the presence of broad peaks in the low frequency region of the Raman spectra of the high temperature phase indicate that the molecules undergo anisotropic rotation. The frequency of the ring inversion mode is highly phase dependent. Keywords: cyclohexene, FT-ir, Raman, phase transition.