Exploring Structure–Property Relationships in Eucalyptol and 1-Alkanol Mixtures: A DFT and Experimental Study

Abstract

This study employs a combined experimental and theoretical approach to investigate the thermophysical properties of eucalyptol (EC) blended with a series of 1-alkanols (ranging from 1-hexanol to 1-nonanol) across a temperature spectrum of 293.15–323.15 K. Density Functional Theory (DFT) calculations at the M05-2x/6-31g(d,p) level of theory are used to optimize the geometry of EC + 1-alkanols and provide insights into the hydrogen bonding interactions between the molecules. The DFT results reveal the significance of alkyl chain length in 1-alkanols on the hydrogen bonding with EC, which is supported by the analysis of geometrical, topological properties, vibrational frequency, NMR, and molecular orbital analysis. The theoretical findings are complemented by experimental measurements of density and viscosity, which show negative deviations from ideality in excess molar volume and viscosity. This study highlights the power of DFT methods in elucidating the molecular-level interactions governing the thermophysical properties of complex binary systems. Furthermore, the DFT results provide a molecular-level understanding of the observed thermophysical behavior, allowing for the development of more accurate predictive models. The integration of experimental and theoretical approaches in this study demonstrates a powerful framework for investigating the properties of complex mixtures.