Polarographic reduction of 1-benzyl-N-(p-X-phenyl)-3-aminocarbonylpyridinium salts

Abstract

The substitution effect of different groups X (N(CH2CH3)2, OH, OCH3, CH3, NHCOCH3, H, Cl, COOCH2CH3 and NO2) on the polarographic behaviour of 3-(N-p-X-phenylaminocarbonyl)pyridines (I), 1-benzyl-N-(p-X-phenyl)-3-aminocarbonylpyridinium cations (II) and their respective 1,4-dihydroderivatives (III) has been investigated in anhydrous solutions of dimethylformamide with 0.1 mol l-1 (n-C4H9)4N+PF6- as supporting electrolyte. The half-wave potentials of the reduction wave of I and II, which correspond to the uptake of a single electron (wave B) and to the formation of a primary radical, obey a Hammett correlation in a similar way as it is in the case of 1-benzyl- and 1-phenyl-3-amino-carbonylpyridinium cations substituted at carbon 4 on the benzene nucleus. The slope ρπ,R in the Hammett plot equals 0.192 V (I) and 0.104 V (II) for anhydrous DMF and compares thus with this slope obtained with the 1-benzyl- and 1-phenyl derivatives in our previous communications.