Densities and electrical conductances of amino acids + ionic liquid ([HMIm]Br) + H2O mixtures at 298.15 K

Densities and electrical conductances of amino acids, glycine, l-alanine and l-valine in aqueous ionic liquid, 1-hexyl-3-methylimidazolium bromide ([HMIm]Br) solutions have been measured at 298.15 K. These data have been used to calculate the apparent molar volumes VϕVϕ, infinite dilution apparent molar volumes Vϕ0, and the standard partial molar volumes of transfer ΔtrVϕ0 of the amino acids from water to the aqueous ionic liquid solutions. It has been observed that both Vϕ0 and ΔtrVϕ0 in the glycine + [HMIm]Br + H2O system increases with increasing ionic liquid concentrations and decrease in the cases l-alanine and l-valine systems. The contribution of the charged end groups (NH3+, COO−), CH2 group and other alkyl chain of the amino acids was estimated using Vϕ0 values. Molar conductivities of [HMIm]Br in aqueous amino acids solutions have been applied for determination of association constants Ka, and limiting molar conductivies Λ0, using the low concentration chemical model (lcCM) of conductance equation.