Potentiometric determination of acidity constants of some Schiff bases in tetrahydrofuran-water mixtures

摘要

Using potentiometric measurements, dissociation constants of two Schiff bases, N,N'-bis(1'-hydroxy-2'-acetonaphthone)propylenediimine (L-1) and bis(1'-hydroxy-2'-acetonaphthone)-3,3'-diiminodpropaneamine (L-2) were determined in binary mixtures of tetrahydrofuran-water at 25.0 +/- 0.1A degrees C and an ionic strength of 0.100 M tetrabutylammonium perchlorate (TBAP). The results show that the pK (a) values of these acids increases as the percentages of the tetrahydrofuran increase in solvent mixtures. There is a linear relationship between acidity constants and the mole fraction of tetrahydrofuran in the solvent mixtures. Effect of solvent composition on acidity constants is also discussed.