Substituent Effect on the Electrooxidation of p-Substituted Aniline and Anisole Derivatives

Sasaki Kazuo, Kitani Akira, Tsuboi Makoto

doi:10.1246/nikkashi.1973.2269

Standard oxidation potentials and anodic half-waves potentials of eleven para substituted derivatives of both aniline and anisble have been determined by means of ordinary dc polaro graphy with a rotating platinum electrode and potential step method. Apparent rate constants for the eleetron transfer in the e1ectrooxidation have also been determined.<BR>The following results were obtained.<BR>1) The standard oxidation potentials determined by means of potential step method were close (within 120 mV, mostly) to the polarographic half-wave potentia for all compounds studied. Accordingly, similar linear correlations were found fer the two petentials with either MO energy or substituent constants.<BR>2) ln the ease of aniline derivatives, the plots of the two potentials against the Brownnkamoto, s constant(showed a straight line with less deviation than the corresponding plots using the Hammett's constant (a). When anisole derivatives were examined, the plots u. sing des s-howed two straight lines with different slopes. Compounds whose points in the above plots fall on the straight line having a smaller slope are considered to. be. oxidizeq with gimultaneous two electrons transfer, and the other compounds are oxidized with one electron transfer. Howeve, the reaction constant, p, was unchanged for the two groups of compounds.<BR>3) Apparent rate constants for the oxidation of aniline derivatives decreased slightly with incieasd of the substituent constant. For anisole derivatives, although points were scattered, there is a definite tendency that a compound having a group of large positive a value is oxidized with slower rate.

Substituent Effect on the Electrooxidation of p-Substituted Aniline and Anisole Derivatives

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