Volumetric, acoustic and IR spectroscopic properties of binary mixtures (1,2-diaminopropane + methyl-, ethyl-, n-propyl- and n-butyl acetates: A combined experimental and first-principles investigation

Studies of density and speed of sound are commonly used tools to ascertain the properties of pure liquids and the nature of interactions between component molecules of a binary mixture. Herein, the density (ρ) and speed of sound (u) of methyl acetate (MAc), ethyl acetate (EAc), n-propyl acetate (n-PAc) and n-butyl acetate (n-BAc) and their binary mixture with 1,2-diaminopropane (1,2-DAP) were measured over the entire composition range at atmospheric pressure 0.1 MPa and in the temperature range of 298.15–318.15 K with a step of 5 K. Different excess thermo-physical properties including the excess molar volume (V_m^E), excess ultrasonic speed (u^E), excess free volume (V_f^E), excess intermolecular free length (L_f^E), and excess molar isentropic compressibility were evaluated from the measured results of ρ and u. The evaluated properties were also analysed in terms of the extent and nature of interactions. The Redlich-Kister polynomial equation was used to correlate the various excess properties to the composition. Further, the u data is analysed by various correlations, Schaaff's collision factor theory (CFT) and Jacobson's free length theory (JFLT). The effect of chain length, branching and temperature on the intermolecular interactions and the magnitude of the measured properties have also been systematically analysed. Furthermore, excess molar properties and the intermolecular interactions have been interpreted in the light of Fourier transform infrared spectroscopy (FT-IR) and density functional theory (DFT) studies. Hydrogen-bonded interactions are predicted to play important role in stabilising the binary mixtures.