1-Ethyl-4-butyl-1,2,4-triazolium acetyl amino acid ionic liquids: preparation and characterization of physicochemical properties

Abstract

In order to address certain performance limitations of imidazolium amino acid ionic liquids, three novel 1-ethyl-4-butyl-1,2,4-triazolium acetyl amino acid ionic liquids, namely [Taz(2,4)][Acgly], [Taz(2,4)][Acala], and [Taz(2,4)][Accys] were synthesized and characterized in this work. Firstly, based on experimentally determined refractive indices and previously reported data including density, surface tension, viscosity, and heat capacity, the polarization properties, surface properties, and volumetric properties were calculated. Special emphasis was placed on elucidating the influence of acetyl amino acid anion structure on the physicochemical properties of these ionic liquids. Subsequently, by integrating molar surface Gibbs energy with the Lorentz–Lorenz relation, we established a predictive equation for surface tension, which demonstrated excellent agreement with experimental values. Analysis using the polarity coefficient equation revealed that the polarity of the ionic liquids decreases with increasing anion side-chain length, corresponding to enhanced hydrophobicity. Finally, the Eyring viscosity equation and thermodynamic formulas were employed to derive a computational expression for viscous flow activation energy, yielding results consistent with those obtained from the Arrhenius equation. Current limited research on 1-ethyl-4-butyl-1,2,4-triazolium acetyl amino acid ionic liquids necessitates combined experimental and semi-empirical approaches to guide their functional design and industrial applications.