Collect. Czech. Chem. Commun.
1998, 63, 31-41
https://doi.org/10.1135/cccc19980031
Electrochemical Study of Acid-Base Properties of Some 2,5-Dihydro-1,3,4-thiadiazoles in Aqueous-Ethanolic Solutions
Maria Turowskaa, Grzegorz Mlostonb, Pawel Krzyczmonika, Jacek Raczaka and Jaroslaw Romanskib
a Department of General and Inorganic Chemistry, University of Lodz, Narutowicza 68, 90-136 Lodz, Poland
b Department of Organic and Applied Chemistry, University of Lodz, Narutowicza 68, 90-136 Lodz, Poland
Abstract
The dissociation constants Ka for spherically crowded 2'- and 2,5-substituted thiadiazolines and their protonated forms in 45% (v/v) aqueous-ethanolic solutions (ionic strength m = 0.1) were determined using the pH-metric method. All the thiadiazoles are weak bases. Some of them showed also weak acidic properties. The formation enthalpies have been calculated using the MNDO method. On the basis of the obtained results the mechanism of the protonation process is discussed.
Keywords: Acidity; Basicity; Thiadiazoles; Dissociation constant; Substituent effect; Semiempirical calculations.
