Influence of dielectric constant on protonation equilibria of maleic acid and L-asparagine in acetonitrile water-mixtures

Abstract

The protonation constants of maleic acid and L-asparagine have been studied pH-metrically in various concentrations (0–50% v/v) of acetonitrile–water mixtures maintaining an ionic strength of 0.16 mol L-1 at 300C. The protonation constants have been calculated using 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.