Tautomerism oxo-enol

The tautomeric oxo-enol equilibrium was studied by MNDO calcuations52 and H NMR and IR spectroscopy.53 It was found that, for 2-aminopyrimido[4,5-d]pyridazine-5,8-diol, the 5,8-dihydroxy tautomer 1 is the most stable form.52 4-(4-Chlorophenyl)pyrimido[4,5-d]pyridazin-2-ol seems to exist in the 2-hydroxy form 2 in dimethyl sulfoxide solution, whereas in the solid state the IR spectrum indicates the oxo form 3.53 IR spectra of 2-substituted pyrimido 4,5-r/]-pyridazine-5,8-diols (R = alkyl, aryl lactam carbonyl absorption at 1630-1650 cm ) revealed the existence of the dioxo form 4 as opposed to the dihydroxy form.54... 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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