SPECTROSCOPIC EVIDENCE FOR PSEUDOROTATION IN CYCLOPENTANE

Abstract

The infrared spectrum of cyclopentane has been examined from 33 to $4000 cm^{-1}$. A series of pronounced Q-branches with a $5 cm^{-1}$ spacing was observed on top of the $CH_{2}$ deformation. The Q-branch frequencies could be reproduced by assuming that the cyclopentane ring was undergoing pseudorotation. The spectroscopically derived parameter $mq^{2}_{o}$ was found to be $(11.0 \pm 0.2) \times 10^{-40}$ g. $cm^{2}$.