Substituent effects on the thioamide group in thiobenzanilides: simultaneous conformational and acid–base equilibria
✍ Scribed by Karel Waisser; Miroslav Polás̆ek; Ivan Nĕmec; Otto Exner
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 68 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0894-3230
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✦ Synopsis
Substituent effects in substituted thiobenzanilides were investigated by the acid dissociation constants in water and the half-wave potentials of the anodic oxidation in acetonitrile; the substituents were chosen with respect to related pharmacological research. The pK values are well correlated by the Hammett equation, and the effects of substituents in the two benzene rings are additive. Since the acid-base equilibrium is combined with an equilibrium of conformers Z E, the general mathematical consequences for a Hammett correlation were calculated. In the common case, a Hammett correlation is not obeyed for the apparent dissociation constants even when it is obeyed for all partial processes. In the present case, the effect of conformation is relatively slight and insufficient to disturb the overall Hammett correlation of the acidities. The half-wave potentials gave bad correlations, only an additive relationship is roughly valid.