Revealing Intermolecular Interactions and Electronic Properties in the Hydrogen-Bonded Complexes of Alcohols-Acetaldehyde at 308 K by Ultrasonic and DFT Studies

Abstract

In this study, we investigated the densities, viscosities, and ultrasonic velocities of binary mixtures of methanol, ethanol, and phenol with acetaldehyde at 308K. We found a positive correlation between concentration and density, with the maximum density occurring at equimolar ratios. Ethanol formed stronger hydrogen bonds with acetaldehyde than methanol due to the presence of hydroxyl and carbonyl groups, while phenol (O-H···O=C), containing an aromatic ring, exhibited the strongest hydrogen bonding with acetaldehyde. FT-IR spectroscopy supported these findings, revealing that the phenol-acetaldehyde mixture had the highest interaction energy, even after accounting for basis set superposition error. HOMO-LUMO analysis demonstrated variations in molecular stability and reactivity. Quantum theory of atoms in molecules (QTAIM) and electron localization function analyses highlighted the stronger hydrogen bonding in phenol-acetaldehyde systems. Non-covalent interaction (NCI) maps revealed three regions: Van der Waals interactions, hydrogen bonding, and steric effects. This research provides critical insights into the molecular interactions within binary mixtures, which have significant implications for chemical engineering, materials science, and formulation stability. Understanding these interactions enables the optimization of mixture properties for various industrial applications, where stable and effective chemical systems are essential for enhancing performance in sectors such as pharmaceuticals, energy, and chemical manufacturing.