Acidity constants and thermodynamic parameters of barbituric and diethylbarbituric acids in water, (water plus tetrahydrofuran), and (water plus Triton X-100) systems

Using potentiometric measurements, dissociation constants of barbituric and diethylbarbituric acid (BA and DEBA) were determind in water, in a tetrahydrofuran + water mixture, and in a water + Triton X-100 micellar system. Results show that the pK(a) value of these acids increases as the percentages of the tetrahydrofuran increase. Similar results were obtained upon addition of a neutral surfactant such as Triton X-100 to the solution of these acids. Thermodynamic parameters of these acids were obtained by determination of the acidity constants of barbituric and diethylbarbituric acids in water at five different temperatures ranging from (15.0 to 55.0) degreesC and at an ionic strength of 0.100 M KCl.