Volumetric Properties of Amino Acids in Aqueous N-methylacetamide Solutions at 298.15 K

The apparent molar volumes (V φ ) of glycine, L-alanine and L-serine in aqueous 0 to 4 mol⋅kg−1 N-methylacetamide (NMA) solutions have been obtained by density measurement at 298.15 K. The standard partial molar volumes (\(V_{\phi}^{0})\) and standard partial molar volumes of transfer (\(\Delta_{\mathrm{tr}}V_{\phi}^{0})\) have been determined for these amino acids. It has been show that hydrophilic-hydrophilic interactions between the charged groups of the amino acids and the –CONH– group of NMA predominate for glycine and L-serine, but for L-alanine the interactions between its side group (–CH3) and NMA predominate. The –CH3 group of L-alanine has much more influence on the value of \(\Delta_{\mathrm{tr}}V_{\phi}^{0}\) than that of the –OH group of L-serine. The results have been interpreted in terms of a co-sphere overlap model.