Experimental and Computational Assessment of Propyl Propionate with 2-Alkanols (C ₃ –C ₇ ): Density, Viscosity, and DFT Analysis

Densities and viscosities were measured for five binary mixtures of propyl propionate (PP) with 2-alkanols ranging from 2-propanol to 2-heptanol over the full composition range at temperatures from 293.15 to 323.15 K. All systems exhibited positive excess molar volumes, with the extent of expansion increasing with both temperature and the length of the alkanol alkyl chain. This behavior is consistent with structure-breaking effects resulting from disruption of self-association in the pure alkanols. Viscosity deviations were negative throughout and increased in magnitude with alkanol chain length, indicating that the mixtures exhibit weaker intermolecular interactions relative to those present in the corresponding pure components. A detailed understanding of hydrogen bonding in complex liquid mixtures is crucial for optimizing process behavior and enhancing predictive thermodynamic models. Experimental measurements elucidate the macroscopic thermodynamic consequences of these interactions, while complementary density functional theory (DFT) calculations provide molecular-level insight into the hydrogen-bonding networks present in propyl propionate +2-alkanol systems. To further refine this perspective, computational studies employing the M05–2X functional with the 6–311++G** basis set were conducted, enabling a more comprehensive characterization of the intermolecular hydrogen-bonding patterns within these mixtures.