H. Azab, I. T. Ahmed, M. Mahmoud
May 12, 1997
Citations
1
Influential Citations
15
Citations
Journal
Journal of Chemical & Engineering Data
Abstract
The apparent dissociation constants of malic acid (hydroxybutanedioic acid), tartaric acid (2,3-dihydroxybutanedioic acid), phthalic acid (1,2-benzenedicarboxylic acid), and succinic acid (butane-1,4-dioic acid) were determined at 25 °C and ionic strength I = 0.10 mol dm-3 KNO3 by potentiometric pH titration in pure water and water + methanol, water + ethanol, water + N,N-dimethylformamide, water + dimethyl sulfoxide, and water + acetonitrile. pKa values increase with an increase in the concentration of the organic solvents. These results are discussed in terms of solvent characteristics. Solvent basicity and stabilization of the conjugate acid free base by hydrogen-bonding interactions in hydroorganic solvent media relative to pure aqueous media as well as proton−solvent interaction play an important role in the acid dissociation equilibrium.