Title : Thermophysical and FTIR properties of different amino acids in aqueous 1-butyl-3-methylimidazolium bromide solutions
Abstract:
Amino acids, as fundamental structural units of peptides and proteins, play an important role in biological systems by influencing biomolecule solubility, denaturation, and activity. The investigation of these effects on the thermophysical properties of model compounds in the presence of electrolytes solutions provides insight into solute-solvent and solute-solute interactions on biomolecules. Ionic liquids (ILs) as organic electrolytes and green solvents are composed of an organic cation and an inorganic anion which are liquid at ambient conditions. In the past decade, extensive investigations showed that the use of ILs as reaction media for processes involving biologically relevant compounds is promising in view of their successful application in kinetic resolution, biocatalysis, biosynthesis, separation and purification processes . The scope of this information is useful for investigating the interactions of amino acids in ILs. To reach this purpose, densities (ρ), viscosities (η) and FTIR studies of glycine, L-alanine, L-serine, L-threonine, and DL-α-aminobutyric acid in aqueous 1-butyl-3-methylimidazolium bromide, [BMIm][Br] solutions of different molalities were determined over the temperature range T = (298.15-318.15) K using vibrating-tube digital density meter (DMA 4500M, Anton Paar, Austria), Ubbelohde capillary type viscometer and Perkin-Elmer IR instrument with a diamond ATR (attenuated total reflectance) crystal (MODEL SPECTRUM TWO). Density and viscosity data have been used to calculate various parameters such as apparent molar volumes (V_∅), partial molar volumes? (V?_2^o), viscosity B-coefficients, temperature coefficients( (dB)⁄dT), transfer parameters, i.e.?,??_tr V_2^o and ?_tr B, interaction parameters,? Y?_AB and? Y?_ABB and hydration number i.e.? n?_(H )and N_h. Also, partial molar expansibilities ((∂V_2^o)⁄∂T)_P, their second-order derivatives ((∂^2 V_2^o)⁄(∂T^2 ))_P, and isobaric thermal expansion coefficients (α_IL) were calculated.The charged end groups, D (?-NH?_3^+,-?COO?^- ) and side-chain contributions of the amino acids, D(-R), have also been obtained from V_2^oand viscosity B-coefficients data. Results obtained have been interpreted in terms of amino acids + water + [BMIm][Br] interactions. FTIR data has been interpreted to study the interactions between amino acids and aqueous [BMIm][Br] solutions.
Keywords: 1-butyl-3-methylimidazolium bromide, Density, Viscosity, FTIR
