Motions of Molecules in Condensed Systems III. The Infra-Red Spectra for Cyclohexane Solid II, Solid I, Liquid and Vapor in the Range from 3 to 15μ

Abstract

Infra-red spectra are compared throughout the interval from 650 to 3300 wave numbers for the same amount of cyclohexane when it exists separately as vapor at 20°, liquid at 10°, and solid I at 3°C, likewise in the intervals from 700 to 1600 and 2500 to 3300 wave numbers when it exists as solid I at −75° and solid II at −100°C. The four spectra obtained with the condensed phases are quite similar and differ only slightly from the one for the vapor. These results contrast sharply with ones reported previously for a similar study of benzene and indicate that there is a greater semblance of order in liquid cyclohexane than in liquid benzene. The spectra are consistent with, but yield no constructive evidence to confirm or deny the notion that molecules of cyclohexane are able to rotate freely in solid I. Developments attributable to intermolecular forces, although not spectacular, contain new information about the numbers and positions of bands which may prove useful toward assigning frequencies to normal modes of vibration in the isolated molecule of cyclohexane. The results of this study do not contradict any of the principles set forth in the first paper of this series.