Tautomerism in N-Heterocycles. IV. Pyrazino[2,3-d]pyridazine-5,8-diol

Abstract

Pyrazino[2,3-d]pyridazine-5,8-diol as the neutral molecule in aqueous solution has been shown to exist predominantly as 8-hydroxypyrazino[2,3-d]pyridazin-5(6H)-one by comparison of its u.v.spectra and pK_a values with those of N- and O-methyl derivatives.