Experimental and DFT study of thermo-acoustic and excess properties of aniline with α-, β-, and γ-Picoline at 303.15 K

The experimental and theoretical investigation has been carried out on binary liquid mixtures of aniline with α-Picoline, β-Picoline and γ-Picoline at 303.15 K over the entire composition range. Density ( ρ ) , ultrasonic sound velocity ( u ) , and viscosity ( η ) were measured experimentally, from which various thermo-acoustic and transport parameters such as molar volume ( V m ), adiabatic compressibility ( β S ), intermolecular free length ( L f ), internal pressure ( π i ), relaxation time (τ), and Gibb’s free energy (ΔG) were evaluated. Excess thermodynamic properties including excess molar volume ( V m E ), excess adiabatic compressibility ( β s E ), excess free length ( L f E ), excess internal pressure ( π i E ), excess relaxation time ( τ E ), and excess Gibb’s energy ( Δ G E ) were computed to assess deviations from ideality. Redlich–Kister polynomial fitting was applied to correlate excess parameters and analyze composition-dependent non-ideal behavior. Additionally, quantum chemical calculations were performed using Density Functional Theory (B3LYP/6-311G*) to support the experimental findings and gain insights into intermolecular association. The combined approach reveals significant specific interactions, contributing to a deeper understanding of structural property relationships in aniline with Picoline mixtures.