Application of the hammett equation to the electrochemical oxidation of diaryl chalcogenides and aryl methyl chalcogenides

Abstract

The electrochemical oxidation of symmetrical 4,4′-disubstituted diaryl selenides and tellurides and 4-substituted aryl methyl sulfides, selenides and tellurides has been studied. Peak oxidation potentials show good correlation with Hammett σ_p⁺-values for all series of compounds (diaryl selenides, R= 0.98, n= 10; diaryl tellurides, R= 0.98, n= 14; aryl methyl sulfides, R= 0.97, n= 5; aryl methyl selenides, R= 0.98, n= 5; aryl methyl tellurides, R= 0.98, n= 5). From the slope of the Hammett plots (methyl aryl chalcogenides) it was concluded that the degree of conjugation of a heteroatom with a para-substituent through an aromatic ring decreases in the following order: S > Se > Te. Results from the electrochemical oxidation of unsymmetrical diaryl selenides and tellurides indicate that the heteroatom is interacting with only one of the aromatic rings in diaryl chalcogenides.

¹²⁵ Te chemical shifts of symmetrical 4,4′-disubstituted diaryl tellurides correlate well with Hammett σ_p-values (R= 0.98, n= 13).