Raman spectral investigation of the interactions between group II cations and ethylene glycol in aqueous solutions

Abstract

Studies of the Raman spectra of aqueous solutions of ethylene glycol (EG) containing Group II cations revealed that calcium, zinc, and strontium ions bring about significant changes in the C–C and C–O stretching regions, while magnesium, cadmium, and barium ions result in only minor changes primarily in the C–O stretching region. These changes were compared with the effects of some of the ions on a series of related molecules including methanol and ethanol, the cyclohexane-1,2-diols, and ethylenediamine. The results indicate that the effects of calcium, zinc, or strontium ions on the spectrum of EG are most consistent with bidentate co-ordination of the metal ions and an attendant conversion of ethylene glycol from trans- to gauche- form. The minor changes arising from the presence of magnesium, cadmium, or barium ions are those expected from monodentate co-ordination. The i.r. spectra of solutions of calcium chloride in ethylene glycol reveal changes which are consistent with the interpretation of the Raman spectra.