Partial molar volumes of some dipolar ions in water at 35 °C

Abstract

This work reports partial molar volumes, V 0 , of eight peptides and three other dipolar ions (glycine, diglycine, triglycine, dl-alanyl-dl-valine, glycyl-dl-alanine, glycyl-dl-leucine, glycyl-tyrosine dihydrate, dl-alanyl-glycyl-glycine, l-valyl-glycyl-glycine, l-lysine-l-aspartate, l-lysine-l-glutamate) in water, calculated from density data obtained at 35 °C. V 0 data are interpreted in terms of solute–solvent interactions. In some cases where V 0 data at 25 °C were available from the literature, a comparison indicates that partial molar volumes of these solutes at 35 °C are higher than their respective volumes at 25 °C by about 2–3 cm 3 mol −1 . Partial molar expansibilities, E 0 , were also estimated in such cases. Expansibility data appear to show a trend indicating dependence of E 0 values on the chain length of the solute molecules. Some plausible modes of solute–solute interactions are also discussed. Keywords: hydration of dipolar ions, partial molar volumes of peptides, solute–solvent interactions, electrostriction, solute–solute interactions.