Acid-base properties and structures of 5-hydroxypyrimidine derivatives and their N-oxides

Abstract

The acid-base properties of some 5-hydroxypyrimidine derivatives and their N-oxides were investigated in comparison with the analogous 3-hydroxypyridine derivatives. It was found that 5-hydroxypyrimidines exist in the hydroxy form and are protonated at the nitrogen atom, whereas their N-oxides are protonated at the oxide oxygen atom, in contrast to the N-oxides of other diazines (pyridazine and quinoxaline). The character of the effect of ortho and para substituents (alkyl, benzyl, and phenyl) on the basicities and acidities of the indicated compounds was ascertained.