Volumetric Properties of Glycine, l-Alanine, and l-Serine in Formamide–Water Mixtures at 298.15 K

Abstract

The density of glycine, l-alanine, and l-serine in formamide–water mixtures was measured at 298.15 K and used to calculate the apparent molar volume Vϕ and limiting partial molar volume Vϕ° of the amino acids. Transfer partial molar volume ΔtrVϕ° from water to formamide–water mixtures and the volumetric interaction coefficients were also obtained to interpret the solute–solvent interaction. Values of ΔtrVϕ° of the three amino acids were all positive and increased with increasing formamide concentration in the mixtures, in the order of l-alanine < glycine < l-serine, which was consistent with the cosphere overlap model. The interaction of formamide molecules decreased its structural-breaking effect and consequent interaction with amino acids, leading to negative triplet interaction coefficients.