Infrared Spectra and Molecular Vibrations of Ethylene Glycol and Deuterated Derivatives

The infrared spectra of ethylene glycol and ethylene glycol-d2 have been measured in the liquid and crystalline states in the region 4000—300 cm−1. The infrared and Raman spectra suggest that ethylene glycol molecule takes only the gauche conformation as to the C-C bond in both states (the likely models are TGT, TGG and GGG). To establish the vibrationarassignments, the normal coordinate treatments of ethylene glycol and its three deuterated derivatives have been carried out for these models by the use of GF matrix method. The modified Urey-Bradley force field has been used and the force constants have been transferred from similar molecules. The potential energy distributions have also been calculated and the nature of the observed infrared bands and Raman lines in the liquid state has been discussed. The empirical assignments of the methylene rocking modes by the previous investigators have been revised by the present normal coordinate analyses.