Exploring molecular association of isopropanol-water binary solution by Raman spectroscopy

Abstract

Raman spectra of isopropanol-water binary solution were measured at room temperature and atmospheric pressure in different blending ratios. We found that the hydrogen bonds between water molecules are almost unaffected by isopropanol molecules at low concentration of isopropanol. The symmetric and asymmetric OH stretching vibrations (corresponding to 3225 and 3443 cm-1Raman shift) of water move rapidly to high frequency when the volume fraction of isopropanol (Vi) exceeds 0.2, indicating the change of hydrogen bonds between isopropanol and water molecules. Moreover, the vibration force constant and the electron cloud density of isopropanol-water binary system were investigated due to the frequency shift of the CH3COH scissor vibration in the isopropanol Raman spectra. In addition, CH⋯O of the CH3group of isopropanol and the corresponding molecular association structure were investigated based on the Raman feature at 1452 cm−1. Finally, the phase transition process of association molecules (ring−CHain and chain) have been deeply explored in isopropanol-water binary solution by theoretical analysis.