Raman and Fourier transform infrared spectra of C-H and O-H stretching vibrations in ethanol and its aqueous solutions. Experiment and ab-initio calculations

Abstract

Raman and FTIR spectra of pure ethanol and its proton-donor and proton-acceptor solvents were studied using experiments and ab-initio (DFT) calculations. Spectral bands related to C-H and O-H stretching vibrations of pure ethanol are complex and consist of at least two bands, and these bands belong to different aggregates of ethanol. According to experiments and ab-initio calculations, when ethanol is dissolved in water, the Raman and FTIR spectra related to C-H and O-H stretching vibration shifted towards higher frequency as the concentration of ethanol decreased. This is due to hydrogen bonds in the form of C-H···O (non-classical) and O-H···O. Such shifts take place due to weak interactions between the methyl group in ethanol and water.