Potentiometric Determination of Acidity Constants of Some Synthesized Organic Compounds in Organic-Water Media

The acidity constants of some synthesized protonated pyrazolo quinazoline compounds were determined potentiometrically at ionic strength of 0.1 M in DMF: water (60:40 v/v) system at different temperatures (298.15 K to 318.15 K). The pKa values have been found to increase with increasing electron-donating nature of substitutions. Some thermodynamics parameters such as enthalpy (ΔH°), Gibb’s free energy (ΔG°) and entropy (ΔS°) of reactions have also been evaluated at different temperatures for these systems. The thermodynamic parameters indicate that dissociation process is not spontaneous and exothermic.