Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

In this work, electrical conductivities of the active pharmaceutical ingredient in ionic liquid form (API-IL), 1-butyl-3-methylimidazolium ibuprofenate, [BMIM][Ibu] in water and in the aqueous solutions of amino acids, glycine and L-alanine have been measured at T = (288.15 318.15) K. The calculated molar conductivity data were analyzed by two famous conductivity models, low concentration Chemical Model (lcCM) and Fernandez-Prini (FP). The results show that the FP equation is more appropriate for analysis of the molar conductivity data because the calculated parameters are not highly influenced by the initial guess values of the parameters. Using these models, the limiting molar conductivities (K0), ion association constants (KA) and standard Gibbs energy (DG0 A) for the ion association process of the API-IL have been calculated. The values of K0 and KA decrease as the concentration of amino acid increase. This trend may be attributed to low mobility of the ions with large radii produced during the solvation of the ions by zwitterions of the amino acids. The values of K0 and KA also increase from glycine to L-alanine solutions. The ions of [BMIM][Ibu] are more solvated by (COO /NH3 + ) zwitterionic centers of glycine rather than L-alanine. The more negative values of DG0 A for [BMIM][Ibu] in L-alanine rather than glycine solutions indicates that more spontaneously and more feasibility of the ion association process in this amino acid.