The Vibrational-Spectrum of Sodium Propionate CH₃CH₂CO₂Na, CH₃CD2CO2Na, CD₃CH₂CO₂Na and CD₃CD₂CO₂Na in Aqueous-Solution and in the Solid-State

Abstract

Infrared absorption spectra of aqueous solutions and KBr discs, reflection spectra of the diluted powders and of an oriented thin film, and Raman spectra of the powdered solids have been measured for CH₃CH₂CO₂Na, CH₃CD₂CO₂Na, CD₃CH₂CO₂Na and CD₃CD₂CO₂Na. Selective deuteration makes possible complete vibrational assignments in the CH and CD stretching regions where band overlap is extensive, but produces complicated changes in 1200- 800 cm^-1 range. Average methyl CH stretching frequencies are higher in propionate ion than in paraffins in spite of the interposed methylene group. In the solids the CO stretching vibrations show more frequency splittings than expected for the number of molecules per unit cell (2), and some orientational disorder is indicated. The shape of the anions was not established; there is no evidence indicating the presence of more than one conformation in solution.