MECHANISTIC STUDIES OF OXIDATION OF DIPHENYLMETHANOLS BY SODIUM N-CHLOROBENZENESULPHONAMIDE CATALYSED BY RUTHENIUM(III)

✍ Scribed by K. S. Rangappa; H. Ramachandra; D. S. Mahadevappa

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 182 KB
• Volume: 10
• Category: Article
• ISSN: 0894-3230
• DOI: 10.1002/(sici)1099-1395(199703)10:3<159::aid-poc867>3.0.co;2-v

✦ Synopsis

The kinetics of oxidation of six para-substituted diphenylmethanols (Y-DPM, where Y = H, Cl, Br, NO 2 , CH 3 and OCH 3 ) by sodium N-chlorobenzenesulphonamide [chloramine-B (CAB)] in the presence of HCl and catalysed by RuCl 3 in 30% (v/v) methanol medium was studied at 35 °C. The experimental rate law is rate = kЈ[CAB] 0 [DPM] x 0 [RuCl 3 ] y [H + ] z , where x, y and z are fractions. Addition of reaction product, benzenesulphonamide (BSA), retards the reaction. An increase in the dielectic constant of the medium decreases the rate. Rate studies in D 2 O medium showed that the solvent isotope effect kЈ(H 2 O)/kЈ(D 2 O) = 0•53. Proton inventory studies were carried out using H 2 O-D 2 O mixtures. The rates correlate satisfactorily with the Hammett relationship and the plot is biphasic. The reaction constant is ؊ 2•8 for electronreleasing groups and ؊ 0•31 for electron-withdrawing groups at 35 °C. The activation parameters ⌬H ‡ , ⌬S ‡ , ⌬G ‡ and logA were calculated. ⌬H ‡ and ⌬S ‡ are linearly related and an isokinetic relationship is observed with ␤ = 343 K, indicating enthalpy as a controlling factor.