Electrochemical Reduction of Aza -heteroaromatic Compounds. Part lll. Effect of Anionic Charge on the Reduction Products of Some Carboxylic Acid Derivatives of 1-Methyl-quinolinium Salts

Abstract

Introduction of anionic charge to quinolinium ring, such as quinaldinic- and cinchonic- acid methyl betaine, has no effect on the stabilization of the radicals, because of the decreasing effect of its electron affinity. However, introduction of the anionic charge has an elevating effect on the reducing power of its dimer. The oxidation potential of the dimer was observed at the more negative potential than that of the coresponding dihydro compounds. Proximity of first and second wave in a polarogram of a quinolinium salt, such as cinchonic methyl betaine, suggests some possibility of disproportionation reaction. Rather negative reduction potential of quinolinium ion and a low dimerizing rate of produced radical may be necessary for the disproportionation of the radical. A carboxyl group attached to the sp³ carbon atom on a dihydroquinoline derived from quinaldinic acid methyl betaine has a great possibility of decarboxylation.