Thermodynamic study of mesitylene + alkanol mixtures: Insights into molecular interactions

Excess properties are a powerful tool for understanding the intermolecular interactions in mixtures. In this study, the excess molar volume (VmE), excess isentropic compressibility (κsE) deviation in ultrasonic speed (Δu), and refractive index (ΔnD) were analyzed for mixtures of mesitylene and alkanol to interpret their intermolecular interactions. Our findings demonstrate that positive values of VmE and κsE indicate the predominance of the rupture of H-bonding in self-associated alkanol dominate over the electron donor–acceptor interaction between the hydroxyl group of alkanol and π–electrons of mesitylene. It was also observed that these electron donor–acceptor interactions weaken as the temperature increases. These observations were further supported by the behavior of molecular association parameter (MA), free intermolecular length, and available volume. Among the alkanols studied, n-butanol exhibited the highest value of MA, suggesting a strong degree of molecular association due to favorable intermolecular interactions between the dissimilar molecules. In contrast, sec-butanol showed the lowest value, which can be attributed to the steric hindrance caused by three methyl groups of mesitylene and the two methyl groups attached to a hydroxyl carbon atom in sec-butanol. Regarding correlation, Schaffs collision factor theory demonstrated high predictive power for ultrasonic speed compared to other models.