Triazanaphthalenes hydration equilibrium ratios

Very few values are known for anhydrous organic bases which can undergo covalent hydration, so that, in general, and for such systems cannot be calculated using Eqs. (12) and (13). However, in cases where the pA of the hydrated species can be measured, Eq. (14) can be used to obtain an approximate estimate of K, the equilibrium ratio of hydrated to anhydrous neutral molecules. This treatment has been applied to quinazoline, the nitroquinazolines, and some triazanaphthalenes. 

Triazanaphthalene, although at one time thought to undergo ring-opening under acidic conditions, is now known to form a stable hydrated cation. Examination of the ultraviolet spectra by the stopped-flow technique has shown that the ratio of the hydrated to the anhydrous forms is 95 and 0.0001 for the cation and neutral molecule, respectively, at equilibrium. This substance hydrates in the 1,2-position, Hydration has also been found in the 3-methyl, 3-hydroxy, and 7-amino derivatives, but not in the 2- or 8-hydroxy deriva-tives. ... 

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