Thermodynamic dissociation constants of benzoic and nitrobenzoic acids in mixtures of ethanol and 1-propanol with water at 25�C

Abstract

The molar conductances of dilute solutions of benzoic and 2-, 3-, and 4-nitrobenzoic acids in binary mixtures of ethanol and 1-propanol with water have been measured at 25°C. The data were fitted to the Lee- Wheaton conductance equation for the derivation of thermodynamic dissociation constants and limiting molar conductances. The results were compared with those in literature pertaining to analogous media and with those already found in methanol-water mixtutes. The findings are interpreted in terms of solute- solvent interactions, intramolecular hydrogen bonding, resonance, the inductive effect and the substituent position. The study showed that the dissociation order decreases as 2-nitrobenzoic acid >3-nitrobenzoic acid ≈4-nitrobenzoic acid > benzoic acid, in all three types of alcohol-water mixtures.