Protonation constants of some N-substituted thiophene-2-carboxamidoximes Original Research Article

The stoichiometric protonation constants of some N-substituted thiophene-2-carboxamidoximes have been determined in 50% ethanol–water mixture (v/v) at ionic strength of 0.1 M NaClO4 and at 25°C. A potentiometric titration method was used and calculation was done by using recently developed software. Variations of the protonation constant of these compounds were discussed in view of structural effects exerted on amino nitrogen and thiophenyl moiety by the substituents.