Ultrasonic and Thermodynamic Characterization of Ethyl Benzoate with Branched Butanol Isomers

Abstract

Ultrasonic velocity, density, and viscosity measurements were performed for binary mixtures of ethyl benzoate with 2-methyl-1-propanol and 2-methyl-2-propanol over the full mole fraction range at temperatures from 303.15 to 318.15 K. Thermo-acoustic parameters including molar volume, adiabatic compressibility, intermolecular free length, internal pressure, acoustic impedance, and enthalpy were derived from the experimental data to evaluate intermolecular interactions. Composition dependent variations reveal non-ideal behaviour in both systems. Increasing ester concentration enhances ultrasonic velocity and acoustic impedance while reducing compressibility and free length, indicating strengthened cohesive forces and reduced molecular free volume. The mixture containing 2-methyl-1-propanol demonstrates comparatively stronger interaction effects than the corresponding tert-butanol system, attributed to lower steric obstruction and more effective hydrogen bonding with the ester carbonyl group. Temperature elevation weakens structural organization in both mixtures. The comparative analysis highlights the influence of alcohol branching on acoustic response and thermodynamic behaviour in ester–alcohol systems, providing useful experimental benchmarks for theoretical modelling and industrial formulation design