16.
Mechanistic
Studies of Chloramine-T Oxidation of Dimethyl Sulphoxide in the
Presence of Nano-Range Concentrated Aquachlororhodium (III) Complex
as Catalyst in Perchloric acid: A Kinetic Approach
Bharat Singh*, Anamika Singh and Aniruddh Kumar
Singh
Chemical Kinetics Laboratory, Department of Chemistry, University of
Allahabad, Allahabad-211002, India,
Tel: +91532-2500553 Email:
bschem_au@yahoo.com
Abstract:
The kinetics of oxidation of dimethyl sulphoxide (DMSO) by
Chloramine-T(CAT) in the presence of acidic solution of
aquachlororhodium(III) complex in its nano-concentration range
used as homogeneous catalyst have been investigated at 350C for
the first time. Almost constant values of pseudo-first-order
rate constant (kobs) throughout the variations of [CAT] in the
oxidation of DMSO clearly demonstrate that order of the reaction
with respect to Chloramine-T is unity. The results indicate that
the order with respect to [DMSO] is first and with respect to [Rh(III)]
is less than unity. Decreasing effect of [H+] and zero effect of
variation of ionic strength of the medium on the rate of
oxidation were observed. Addition of p-toluene sulphonamide (PTS)
and variation of [Cl¯] have not affected the rate of oxidation
of DMSO. The results are in accord with a proposed mechanism in
which an electrophilic attack at the sulphur site in DMSO by the
positive chlorine in the complex [RhCl5-(RNCl)]-3(formed between
reactive species of Rh(III) chloride and chloramine-T) takes
place in slow and rate determining step to form an intermediate
which finally changes into product through a series of fast
steps with regeneration of effective species of catalyst.
Keywords: Mechanism, Rh(III) catalysis, Oxidation,
DMSO, Chloramine-T, HClO4
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