Thermodynamic acidity constants of ortho-substituted benzenethiols

Abstract

Thermodynamic acidity constants for a series of ortho-substituted benzenethiols have been measured in water at 25°C by an e.m.f.–spectrophotometric method. Analysis of the substituent effects in terms of free energy relationships suggests that the dominant substituent interaction is electronic. Other minor effects appear to operate for the alkyl, methoxy-, and methylthio-substituents, while intramolecular hydrogen bonding is important for o-nitrobenzenethiol.