Thermodynamic, Ultrasonic, and Transport Study of Binary Mixtures Containing 1-Hexene and Alcohols at 293.15–303.15 K

In this paper, densities, speeds of sound, and refractive indices of binary mixtures 1-hexene with methanol, 1-propanol, or 1-pentanol were measured in the temperature range from 293.15 K to 303.15 K, over the whole composition range and atmospheric pressure. Experimental values were used to calculate the isentropic compressibility (κ_s), intermolecular free length (L_f), specific acoustic impedance (z), relative association (R_A), relaxation strength (r), and Rao’s molar sound function (R). From this data, excess/deviation properties of all studied mixtures were calculated and correlated as a function of temperature using the Redlich–Kister polynomial equation. The density of binary mixtures of 1-hexene with alcohols was predicted by using the Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state. Schaaff’s Collision Factor Theory (SCFT) and Nomoto’s Relation (NR) were also applied to model the experimental speed of sound data for these mixtures. Moreover, the refractive index experimental data were analyzed by using widely recognized mixing rules from the literature. Density functional theory (DFT) calculations were conducted to complement the experimental study by analyzing the molecular-level electronic properties of the binary mixtures. Key descriptors such as HOMO–LUMO energy gaps, chemical hardness, and electrophilicity indices provided insights into the reactivity and stability of 1-hexene and alcohol mixtures across the studied temperature range.