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.