Infra-Red Spectra of Propane, 1-Deuteropropane, and 2-Deuteropropane and Some Revisions in the Vibrational Assignments for Propane

Abstract

The infra‐red spectra of propane, 1‐deuteropropane, and 2‐deuteropropane are presented. The spectrum of propane does not have the bands at 720 and 1179 cm⁻¹ reported by Wu and Barker. The vibrational modes of the three molecules are described. The 748‐cm⁻¹ band in the propane spectrum is unambiguously assigned to rocking of the CH₂ group about an axis normal to the molecular axis and in the C₃ plane; and the 1053‐cm⁻¹ band is unambiguously assigned to rocking of the CH₂ group about an axis normal to the C₃ plane. Unambiguous assignments for the remaining bands below 1350 cm⁻¹ in the propane spectrum were not possible without an elaborate theoretical treatment beyond the scope of this paper.