Influence of Dielectric Constant on Protonation Equilibria of L-Aspartic Acid in Acetonitrile- and Ethylene Glycol-Water Mixtures

The protonation constants of L-Aspartic acid have been studied pH-metrically in various concentrations (0–60% v/v) of acetonitrile- and ethylene glycol-water mixtures maintaining an ionic strength of 0.16 mol L–1 at 303K. The protonation constants have been calculated with the computer program MINIQUAD75 and are selected based on statistical parameters. Linear variation of step-wise protonation constants (log K) with the reciprocal of the dielectric constant of the solvent mixture has been attributed to the dominance of the electrostatic forces.