Volumetric and Conductometric Behavior at T = 298.15 K of 2-[(2-Aminoacetyl)amino]acetic Acid, 2-[(2-Aminoacetyl)amino]-3-methylbutanoic Acid, and (2S)-2-[(2-Aminoacetyl)amino]-4-methylpentanoic Acid with Sodium Hexanoate

摘要

Densities and conductivity data for aqueous solutions of 2-[(2-aminoacetyl)amino]acetic acid (commonly known as glycylglycine), 2-[(2-aminoacetyl)amino]-3-methylbutanoic acid (common name glycyl-L-valine), and (2S)-2-[(2-aminoacetyl)amino]-4-mefhylpentanoic acid (commonly known as glycyl-L-leucine) with sodium hexanoate (commonly known as sodium caproate) were determined at T = 298.15 K. The apparent molar volumes of the dipeptides (V_(2,φ)) and limiting molar conductivity of sodium caproate (Λ_o) have been derived. The standard partial molar volumes V°_(2,φ), obtained from V_(2,φ) have been used to calculate the standard partial molar volumes of transfer, △_tV° for glycyl dipeptides from water to aqueous sodium caproate solutions. The hydration numbers, n_H, and volumetric interaction coefficients have also been calculated. The dependence of above thermodynamic functions on concentration and nature of solute has been discussed in terms of various interactions taking place between hydrophobic and hydrophilic parts of peptides and sodium caproate. The decrease in Λ_o values of sodium caproate with an increase in dipeptide concentration is attributed to the interaction of sodium caproate with the dipeptides and increasing viscosity of solvent. The limiting ionic molar conductivities and the Stokes' radii of Na~+ and the caproate anion were also estimated and discussed.