Mechanism and kinetics of the vanadium-catalyzed o-dianisidine—t-butyl hydroperoxide reaction in non-aqueous media

✍ Scribed by M. Otto; J. Stach; R. Kirmse

• Book ID: 102980086
• Publisher: Elsevier Science
• Year: 1983
• Tongue: English
• Weight: 705 KB
• Volume: 147
• Category: Article
• ISSN: 0003-2670
• DOI: 10.1016/0003-2670(83)80093-2

✦ Synopsis

The vanadium-catalyzed oxidation of o-dianisidine by t-butyl hydroperoxide is studied for the determination of trace vanadium in non-aqueous media. In acetonitrile, vanadium acts as a one-electron mediator between the reductant and oxidant. Mechanistic studies, based on e.p.r. spectrometry and visible spectrophotometry, show that the hydroperoxide oxidizes vanadium(IV) via a radical mechanism. The kinetics of V(IV) oxidation are investigated and a rate equation is proposed. Oxidation of o-dianisidine by the vanadium-(V) formed in a one-electron step with formation of the o-dlanisidine radical completes the catalytic cycle, as shown by spectroelectrochemical measurements. The radical reacts further with excess of t-butyl hydroperoxide to form the diimine, which may be used for sensitive spectrophotometric monitoring of the indicator reaction at 450 nm.