RESUMO
The basic ionization (pk 1) and acidic ionization (pk 2) constants and equilibrium constant (K T) of 2HPy and 2MPy were determined. The pk 1(s) of their N- and X-methyl derivatives (X = O, S) were also determined. The equilibrium constant of 2MPy is approximately 60 times greater than its oxygen analog, 2HPy. The micro-ionization constants of the functional groups, -NH (pk A and pk C) and -XH (pk B and pk D), were determined to provide further insights into the ionization equilibria of these N-heteroaromatic XH compounds (2HPy and 2MPy). The relaxation time of water (τ) in aqueous solutions of 2HPy and 2MPy are collectively used with the K T values to determine the forward (k f) and backward (k b) rate constants of tautomerization. Subsequently, the k f and k b are used to provide the rationale for the K T and τ values.
