Infrared Study of Ethylene Carbonate in Various Solvents and Solvent Systems

The vC=O frequency for ethylene carbonate is in Fermi resonance with the first overtone of the skeletal breathing mode, and the extent of Fermi interaction is affected by solvent/solvent interaction. The vC=O frequencies have been corrected for Fermi resonance, and the corrected vC=0 frequencies have been correlated with the mole % CHCl 3 /CCl 4 , (CH 3 ) 2 SO/CCl 4 ,(CH 3 ) 2 SO/CHCl 3 , and CHCl 3 / n-C 6 H 14 , the solvent reaction field, and vC=O for acetone recorded in the same solvents. Solute/solvent interactions are discussed. The acceptor number of the solvent vs. the vC=O frequencies apparently correlates in a different manner for the solvents which form intermolecular hydrogen bonds with the solute. Steric factors are suggested as being one of the reasons that the AN values and vC=O frequencies do not give nonambiguous correlations. The vC=O mode for ethylene carbonate shifts continuously to lower frequency as the mole % CHCl 3 or (CH 3 ) 2 SO increases in each of the solvent mixtures studied.