Thermodynamic Studies of Dissociation Reactions of Some Dicarboxylic Acids in 20% (w/w) Acetonitrile - Water Mixture

Abstract

p K1 and p K2 values at zero ionic strength of some dicarboxylic acids (succinic, tartaric, malonic, malic and maleic) in 20% (w/w) acetonitrile-water at temperatures ranging from 30 °C to 60 °C have been determined using a precise EMF method. The thermodynamic parameters Δ H°, Δ G° and Δ S° of the first and the second dissociation reactions are calculated from well known equations and discussed in terms of solute-solvent interactions. An extrathermodynamic analysis of the obtained results has been performed and indicates that these dissociation reactions are entropy-controlled reactions where solute-solvent interaction plays an important role.