A combined Raman spectroscopic and DFT-RDG analysis: unveiling hydrogen-bond networks in glycerol-water mixtures

Abstract Glycerol is a polyol molecule with three hydroxyl groups, its simple structure and strong hydrophilicity make it widely used in hydrogen bonding studies and in the analysis of molecular interactions. In this study, Raman spectroscopy was employed to investigate the evolution of hydrogen bond networks and intermolecular interactions in glycerol-water solutions at varying molar ratios. Analysis of peak position shifts, intensity changes, and O–H stretching vibrations revealed how glycerol concentration modulates the hydrogen-bond structure in aqueous solutions. Additionally, the O-H stretching region of glycerol was investigated. Density functional theory (DFT) and reduced density gradient (RDG) analysis revealed changes in the glycerol hydrogen-bond network. At low water content (1:1), hydrogen bonds are concentrated and intense. As the water ratio increases (1:2, 1:3), the hydrogen bond network gradually expands and becomes more complex, as shown by a broader distribution of vibrational frequencies and broadened spectral peaks. Additional theoretical Raman spectra were calculated for glycerol–water complexes at 1:4 and 1:5 molar ratios, showing only marginal spectral changes compared with the 1:3 system, which suggests that further hydration leads to incremental rather than qualitative modifications of the hydrogen-bonding environment. This study elucidates the molecular interaction in of polyol-water systems, providing a theoretical basis for investigating hydrogen bond dynamics in complex aqueous solutions.