Tautomeric azines. Part V. Cinnolin-3(2H)-one and 3- and 4-aminocinnoline

Abstract

The title compounds are shown to exist predominantly as the structures named in aqueous solution. Their tautomeric equilibria with the relevant hydroxy, imino, and zwitterionic forms are investigated by u.v. spectroscopy and basicity measurements as are the structures of the mono- and di-cationic species. The quantitative tautomeric equilibrium constants are compared with those for the pyridazine and quinoline series.