Solute-solvent interactions of amino acid l-phenylalanine in aqueous 1-butyl-2,3-dimethylimidazolium bromide ionic liquid solutions

Abstract

Densities of l-phenylalanine in water and in aqueous1-butyl-2,3-dimethylimidazolium bromide solutions, at T=(283.15, 288.15, 293.15, 298.15 and 303.15)K and atmospheric pressure have been measured. The apparent molar volumes, VФ, standard partial molar volumes, VФ0, limiting apparent molar expansibilities, EФ0, and standard partial molar volumes of transfer, ΔVФ0, have been calculated. The values of ΔVФ0 are negative. These volumetric parameters are interpreted in terms of various mixing effects between l-phenylalanine and [BMMIm]Br in aqueous solution. The 1H NMR measurements of binary mixtures of l-phenylalanine and [BMMIm]Br in D2O solutions have been carried out to understand the possible interactions. The results show that the interactions between the hydrophobic-hydrophobic groups of [BMMIm]Br and l-phenylalanine may be dominant in the studied system. Furthermore, the density functional theory calculations provide stabilization energies and suggest possible interaction ways that support the volumetric and NMR measurements.