Covalent hydration qualitative

Addition of water across a C=N bond in a conjugated system breaks the conjugation and alters the electronic transitions. The ultraviolet and visible spectra of anhydrous and hydrated species are therefore usually dissimilar, and such differences have been used as the basis for much of the qualitative and quantitative work done on covalent hydration. 

E. Rapid-Reaction Technique Because this technique and the apparatus involved are considered in detail in the following review, only a qualitative discussion is given here. This is the most valuable method for the confirmation of covalent hydration because it can usually give conclusive results even when the percentage of the hydrated species is as low as 2%. It makes use of the facts that aU known examples of the formation or disappearance of the hydrated species followed first-order kinetics and that the rates are both acid- and base-catalyzed. It also depends on the usual state of affairs that the ratio of the hydrated to the anhydrous species, although pH independent (see Section II, A), is different in the three species, i.e. in the cation, neutral species, and anion. In principle, a solution of one... 

Of all the heteroaromatic compounds that have been examined qualitatively and quantitatively for covalent hydration, the pteridines constitute the largest series. Most of the quantitative relationships which were used in earlier discussions were first derived for the hydroxypteridines. Also most of the known examples of hydration in anions were found in this series. 

Covalent Hydration in Nitrogen-Containing Heteroaromatic Compounds I, Qualitative Aspects A. Albert and W. L. F. Armarego, Adv. Heterocycl. Chem., 1964, 4, 1-42. Covalent Hydration in Nitrogen Heteroaromatic Compounds II, Quantitative Aspects D. D. Perrin, Adv. Heterocycl. Chem., 1964, 4, 43-73. 

Albert, A., Armarego, W. L. F., Covalent Hydration in Nitrogen-Containing Heteroaromatic Compounds. I. Qualitative Aspects, 4, 1. 

Covalent Hydration in Nitrogen-Containing Heteroaromatic Compounds I. Qualitative Aspects... 

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