Partial Molar Volumes of Organic Compounds in Water Part 5. Betaines of a/o-Aminocarboxylic Acids

Abstract

The partial molar volumes of a number of ω-(N,N,N-trimethyl-amino)-α-carboxylic acids in water at 25°C have been measured, and related to their van der Waals volumes. The effects of progressive methylation of the nitrogen atom are examined and volume changes arising from electrostriction of the solvent or hydrophobic hydration effects are deduced. It is shown that the interaction of the trimethylalkylammonium group in the betaines with the solvent is identical to that of the alkylammonium group with the solvent in the corresponding aminoacids.