Density and Refractive Index of Mixtures of Hexafluorophosphate- and Bis(trifluoromethylsulfonyl)imide-Based Ionic Liquids with 2-Pentanol, Vinyl Butyrate, 2-Pentyl Butyrate, and Butyric Acid in the Range of 293.15 to 343.15 K at 0.1 MPa

Abstract

Abstract Experimental density and refractive index data were measured for six ionic liquids (ILs) (three hexafluorophosphate-based: [Bmim+][PF6–], [Hmim+][PF6–], [Omim+][PF6–]; and three bis(trifluoromethylsulfonyl)imide-based: [Emim+][NTf2–], [Hmim+][NTf2–], [Omim+][NTf2–]) and their binary mixtures with rac-2-pentanol, vinyl butyrate, rac-2-pentyl butyrate, and butyric acid over the temperature range of 293.15–343.15 K at 0.1 MPa. These systems are relevant due to the role of S-2-pentanol as a chiral intermediate in the synthesis of anti-Alzheimer drugs targeting β-amyloid pathways, and its production by enzymatic kinetic resolution of rac-2-pentanol using lipase-catalyzed transesterification with vinyl esters, which requires accurate thermophysical data in IL media. The experimental data were analyzed through excess molar volumes, apparent and partial molar properties, and infinite dilution functions to elucidate intermolecular interactions and packing effects. Temperature- and composition-dependent polynomial correlations were applied, showing excellent agreement with experimental values. The refractive index data were modeled using mixing rules, with the Wiener model providing the best performance. Deviations in volumetric and optical properties were interpreted in terms of molecular size, polarity, and polarizability, highlighting the influence of the IL structure on mixture nonideality. Overall, this work provides a consistent thermophysical data set and reliable correlations for IL-based mixtures, supporting their characterization and potential application in biocatalytic synthesis relevant to anti-Alzheimer drug production.