IR Spectroscopy of Ethylene Glycol Solutions of Dimethylsulfoxide

Abstract

Features of ethylene glycol (EG) solutions of dimethylsulfoxide (DMSO) with low and moderate concentrations (from 2 to 50 mol % of DMSO) are studied by IR spectroscopy on a Bruker Tensor 37 FT-IR spectrometer in the wavenumber range of 400 to 4000 cm⁻¹. The main monitored bands are the S=O stretching vibration band of DMSO (1057 cm⁻¹) and the C–O (1086 and 1041 cm⁻¹) and O–H (3350 cm⁻¹) stretching vibration bands of EG. The obtained data show complex DMSO · 2EG to be present in all solutions with the studied concentrations due to formation of H-bonds between the S=O group of DMSO and the OH group of EG. In the concentration range of 6 to 25 mol % DMSO, the OH stretching vibration of EG is found to be broadened (by up to 70 cm⁻¹), suggesting the strengthening of hydrogen bonds in the spatial network of the system due to the solvophobic effect of DMSO molecules and the formation of DMSO · 2EG. Starting from 25 mol % DMSO, narrowing of the OH stretching vibration is noted, and the bands of free DMSO appear along with the DMSO · 2EG complex, suggesting microseparation in the investigated system. At 50 mol % DMSO, the amounts of free and bound species in the system became comparable.