Studies on Molecular Interactions in Liquid Mixture of Trimethylamine and Benzene

Abstract

Molecular interactions in liquid mixtures play a significant role in determining the physicochemical properties of chemical systems and are essential for understanding solution behavior in industrial and research applications. The present study investigates the molecular interactions in binary liquid mixtures of trimethylamine and benzene over a range of compositions at controlled temperatures. Experimental measurements of fundamental thermophysical properties, including density, viscosity, ultrasonic velocity, and refractive index, were carried out using standard laboratory techniques. From these experimental data, various excess and derived acoustic parameters such as excess molar volume, viscosity deviation, isentropic compressibility, intermolecular free length, acoustic impedance, and excess Gibbs free energy of activation for viscous flow were evaluated to elucidate the nature and strength of molecular interactions. The observed deviations from ideal behavior indicate that the interactions between trimethylamine and benzene arise primarily from weak donor–acceptor interactions, dipole-induced dipole forces, and dispersion forces rather than strong hydrogen bonding. The composition-dependent variations in excess functions reveal changes in molecular packing efficiency and structural arrangement within the liquid mixtures. Negative and positive deviations in the evaluated parameters reflect the competing effects of molecular association and dissociation, influenced by the size, polarity, and electronic characteristics of the constituent molecules. The experimental results were analyzed using appropriate theoretical and empirical models to assess the reliability of the observed trends and to correlate the thermodynamic behavior of the system. The findings contribute to a deeper understanding of intermolecular forces governing binary liquid mixtures and provide valuable thermodynamic data for chemical process design, solvent selection, separation technologies, and molecular modeling. This investigation enhances the fundamental knowledge of solution chemistry and offers useful insights into the physicochemical behavior of trimethylamine–benzene mixtures under varying compositional conditions.