Controlled Potential Coulometry of 4‐Cyano‐1‐Methylpyridinium Ion in Acetonitrile

Abstract

The electrochemical reduction of 4-cyano-l-methylpyridinium ion in acetonitrile has been studied using controlled potential coulometry in conjunction with d-c polarography and u.v.-visible spectroscopy. In our previous polarographic study, the pyridinyl radical formed at the potential of the first wave was found to be stable, whereas the anion formed at the second wave could react with the parent pyridinium ion to form a dimer. On the longer time scale of coulometry, both anion and radical form this dimer, which subsequently loses two cyanide groups to yield the Paraquat dication. If the reduction potental is set at the first wave, the Pa.raquat dication is then further reduced to the radical cation by the pyridinyl radical in solution. Reduction at the second wave causes the Paraquat dication to be reduced even further to the neutral bipyridyl. The nature of the intermediate dimer is discussed. It seems quite possible that disproportionation of the pyridinyl radical to pyridinium ion and anion may be a step in the dimerization of the pyridinyl radicals.

The electrochemical reaction of methyl pyridinium chloride in acetonitrile

“…Although there was little direct information in the area, a fairly good understanding of the electrochemical behavior of pyridinium salts was available [2,6,[11][12][13][14][15]. In previous research [15], we synthesized 1, r-dimethyl-4,4'-bipyridinium diiodide (DMPI) using an electrochemical method where DMPI was formed by first reducing methyl pyridinium iodide (MPI) on the cathode and then oxidizing it in air.…”