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Ruthenium(III)‐catalyzed mechanistic studies of oxidation of benzhydrols by sodium N ‐chloro‐ p ‐toluenesulfonamide in HCl medium
Author(s) -
Ramachandra H.,
Mahadevappa D. S.,
Rangappa K. S.,
Gowda N. M. Made
Publication year - 1997
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/(sici)1097-4601(1997)29:10<773::aid-kin6>3.0.co;2-j
Subject(s) - chemistry , catalysis , ruthenium , solvent , ionic strength , hydrochloric acid , kinetics , enthalpy , kinetic isotope effect , medicinal chemistry , reaction rate constant , sodium , chloride , reaction rate , inorganic chemistry , nuclear chemistry , organic chemistry , aqueous solution , deuterium , physics , quantum mechanics
The kinetics of oxidation of benzhydrol and its p ‐substituted derivatives (YBH, where Y=H, Cl, Br, NO 2 , CH 3 , and OCH 3 ) by sodium N ‐chloro‐ p ‐toluenesulfonamide or chloramine‐T (CAT), catalyzed by ruthenium(III) chloride, in the presence of hydrochloric acid in 30% (v/v) MeOH medium has been studied at 35°C. The reaction rate shows a first‐order dependence on [CAT] O and a fractional‐order each on [YBH] O , [Ru(III)],and [H + ]. The reaction also has a negative fractional‐order (−0.35) behavior in the reduction product of CAT, p ‐toluenesulfonamide (PTS). The increase in MeOH content of the solvent medium retards the rate. The variation of ionic strength of the medium has negligible effect on the rate. Rate studies in D 2 O medium show that the solvent isotope effect, k ′H 2 O/ k ′D 2 O, is equal to 0.60. Proton inventory studies have been made in H 2 O(SINGLEBOND)D 2 O mixtures. The rates correlate satisfactorily with Hammett σ relationship. The LFE relationship plot is biphasic and the reaction constant ρ=−2.3 for electron donating groups and ρ=−0.32 for electron withdrawing groups at 35°C. Activation parameters Δ H ≠ , Δ S ≠ , and Δ G ≠ have been calculated. The parameters, Δ H ≠ and Δ S ≠ , are linearly related with an isokinetic temperature β=334 K indicating enthalpy as a controlling factor. A mechanism consistent with the observed kinetics has been proposed. © 1997 John Wiley & Sons, Inc.