Ionic equilibria in neutral amphiprotic solvents: Structural effects on dissociation constants of several substituted phenols and mercaptopyrimidines in isopropyl alcohol.
The dissociation constants of several families of acids (substituted phenols and mercaptopyrimidines) in isopropyl alcohol medium have been determined by potentiometric titration with tetrabutylammonium hydroxide. Because of ion-pair formation the incomplete dissociation of the tetrabutylammonium salt has been taken into account in the calculation of pK(a). The dissociation constants of the salts were previously measured conductometrically. The resolution of acid strength in isopropyl alcohol relative to that in water has been determined for each series of acids by plotting the pK(a) values in isopropyl alcohol vs. those in water. The results show greater resolution in isopropyl alcohol than in water. The resolution of acid strength in tert-butyl alcohol relative to that in isopropyl alcohol has also been determined.
Bosch
E
E
Departamento de Química Analítica, Universitat de Barcelona, Barcelona Spain.
Ràfols
C
C
Rosés
M
M