Abstract
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.