Substituted Methanes. I. Raman and Infra-Red Spectral Data, Assignments, and Force Constants for Some Tribromomethanes

Abstract

As a part of a systematic investigation of the vibrational spectra of substituted methanes and ethanes, Raman displacements, semiquantitative relative intensities, quantitative depolarization factors, and infra‐red absorption frequencies in the region 700–5000 cm⁻¹ have been obtained for CBr₃H, CBr₃Cl, and CBr₄. Details about the design of the infra‐red spectrograph are given. The Raman and infra‐red spectral data in the literature for CBr₃H, CBr₃D, CBr₃F, CBr₃Cl, and CBr₄ have been collected, tabulated, and critically examined in comparison with the present results and a decision was made as to the probable values of the Raman and infra‐red data at the present time. Assignments of the observed Raman and infra‐red bands, consistent with the selection rules, were made for all of the molecules. Finally, force constants were calculated for the five molecules, using a potential energy function containing all possible second degree terms.