Electrochemical Behavior of Pyridazine and Cinnoline in N, N Dimethylformamide- Water Systems

Abstract

The electrochemical reduction of pyridazine and cinnoline in N, N-dimethylformamide (DMF), DMF-water containing 0-100 vol% water and Britton-Robinson buffer solution at a mercury electrode was investigated by voltammetry, controlled potential coulometry and spectroscopic methods.
A series of experimental data indicates the following mechanisms for the electrode reaction of pyridazine and cinnoline in DMF-water and buffer solution.
Dihydropyridazine and dihydrocinnoline formed by the controlled potential electrolysis of pyridazine and cinnoline (0.4 mmol/dms) in DMF containing 2% or 4% H₂0 at a mercury pool cathode were confirmed by gas chromatography-mass spectrometry. In the case of concen-trated solution (20 mmolidms) of cinnoline in DMF-H₂0 (above 80%) and buffer solution, however, precipitates were deposited by the controlled potential electrolysis with total charge passage of 0.8-1.2 electron per molecule. Mass spectra revealed that these precipitates were made up of polymerized cinnoline.