Reversible hydration across CN bond in polyazanaphthalenes and their derivatives

Abstract

Reversible hydration to a number of substances named in the title is acid-base catalyzed. The details of the manner of the catalysis are discussed. Because of the reversible nature, the relationship between the rates and equilibria involved in these reactions has been demonstrated for a series of compounds. Reversible hydration of 2,6-dihydroxypteridine in aqueous solutions can give rise to two different water-adducts, the 3,4-adduct and the 7,8-adduct. Although the thermodynamically less stable product, the 3,4-adduct, is formed more rapidly in the solution, thereafter, isomerization occurs, leading to an equilibrum mixture of the two isomers, the 7,8-adduct being the major species at equilibrium. The kinetics and equilibrum studies of these reactions have led to definition of the appropriate conditions under which high yields of the less stable reaction product may be obtained.