INVESTIGATION OF THE STRUCTURE OF AND THE PROPERTIES OF THE POTENTIALLY TAUTOMERIC ,7-DIMETHYL-6H-PYRROLO[3,4-D]PYRIDAZINE-1,4-DIONES IN THE GASEOUS AND AQUEOUS PHASES USING THE AM1 SEMIEMPIRICAL METHOD

Potentially tautomeric ,7-dimethyl-6H-pyrrolo[3,4-d]pyridazine-1,4-dio nes and their fixed tautomeric forms have been studied in order to pre dict their tautomeric equilibrium constants and pK(a) values using sem i-empirical AM1 quantum-chemical calculations at the SCF level in the gas phase and in aqueous solution. Hydroxy-oxo forms were found to be more stable than dioxo and dihydroxy forms. The results obtained from the tautomeric equilibria and basicity calculations are in good agreem ent with experimental data. (C) 1998 Elsevier Science B.V. All rights reserved.