Pseudorotation dynamics in liquid cyclopentane by Raman spectroscopy

We have measured isotropic Raman spectra of cyclopentane-d9 in the CH stretching region from 180 to 300 K. The spectra show what is apparently a partial motional averaging of the CH stretching bands by pseudorotation, a barrierless conformational rearrangement. We have fit the experimental spectra with a model in which the pseudorotation dynamics are described as one-dimensional diffusion on a ring, with an exponentially decaying temporal memory function. Although the fit to the data is good the resulting values of the parameters indicate that the model is unsatisfactory and that inertial behavior must be included. © 1989.