Tautomeric pyridines. Part XV. Pyridone–hydroxypyridine equilibria in solvents of differing polarity

Tautomeric equilibria of the hydroxypyridine–pyridone type are investigated for five compounds: the proportion of pyridone form, dominant for H2O solutions, falls roughly linearly with the solvent polarity as measured by Z. In cyclohexane solution, comparable amounts of both forms are present.