Electrochemistry in pyridine-IV. Chemical and electrochemical reduction of pyridine

Abstract

The cathodic polarographic wave observed for solutions of AlCl3 in pyridine is due not to reduction of Al(III), but to reduction of the solvent, in which process Al(III) plays an essential role, apparently by polarizing the pyridine through the formation of a Lewis acid-base adduct with the pyridine nitrogen. Macroscale electrolysis of pyridine solutions of AlCl3 at a mercury cathode results in the reduction of pyridine and the formation, after hydrolysis and air oxidation, of a complex mixture or copolymer of unsaturated polyamines and polyamides probably containing such units (moities) as: (-. CH:CH . CH2 . NH . CH--)[chi], and (-CH2 . CH2 . CH:CH . CO . NH--)[chi]. Essentially the same product is obtained by treatment of pyridine with LiAlH4. The reaction mechanisms proposed involve disruption of a C---N bond in pyridine.