Insights on hydrophobic groups and Raman characteristics in an ethanol-water system

This study presents an analysis of the ethanol-water system with increasing water content using density functional theory (DFT) in conjunction with Raman spectroscopy. The combined effects of conventional and unconventional hydrogen bonding generate oscillations in the C-O and C-H parameters and charge transfer near the molecule. Consequently, the spectral peaks exhibit both red and blue shifts. The symmetric stretching strength of hydrophobic groups in ethanol molecules initially increases and then decreases. Both the symmetric and asymmetric stretching modes respond to variations in water content in two stages, with symmetric stretching preceding and lagging behind asymmetric stretching. The shift in the OH stretching model suggests that hydrogen bonding reaches its strongest point and tends to stabilize at a water volume fraction of 0.5∼0.6. This study provides insight into the vibrational and hydrogen bonding properties of hydrophobic groups in an ethanol-water system.