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MECHANISTIC STUDIES OF OXIDATION OF DIPHENYLMETHANOLS BY SODIUM N‐ CHLOROBENZENESULPHONAMIDE CATALYSED BY RUTHENIUM(III)
Author(s) -
Rangappa K. S.,
Ramachandra H.,
Mahadevappa D. S.
Publication year - 1997
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(199703)10:3<159::aid-poc867>3.0.co;2-v
Subject(s) - chemistry , reaction rate constant , ruthenium , kinetic isotope effect , enthalpy , kinetics , methanol , medicinal chemistry , solvent , hammett equation , nuclear chemistry , catalysis , organic chemistry , deuterium , physics , quantum mechanics
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= k′ [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 k′ (H 2 O)/ k′ (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 σ relationship and the plot is biphasic. The reaction constant ρ is −2·8 for electron‐releasing groups and −0·31 for electron‐withdrawing groups at 35 °C. The activation parameters ΔH ‡ , ΔS ‡ , ΔG ‡ and log A were calculated. ΔH ‡ and ΔS ‡ are linearly related and an isokinetic relationship is observed with β=343 K, indicating enthalpy as a controlling factor. © 1997 by John Wiley & Sons, Ltd.