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1.
Environmentally Benign Mechanistic Studies of Aquachlororhodium
(III) Complex Catalysis in Oxidation of D-threonine by aqueous
alkaline Chloramine-T : A Kinetic Approach
Bharat Singh*, Anamika Singh, Sandeep Kumar Mishra and Shipra
Tripathi
Chemical Kinetics Laboratory, Department of Chemistry, University of
Allahabad, Allahabad-211002, India,
E-mail:
bschem_au@yahoo.com
Abstract.
The kinetics of aquachlororhodium(III) complex catalysis in
oxidation of D-threonine by alkaline solution of Chloramine-T
(CAT)have been investigated in the temperature range 30° C
to 45°C. Almost constant values of pseudo-first-order rate
constant (kobs) throughout the variation of [CAT] in the
oxidation of D-threonine clearly demonstrate that order of
the reaction with respect to Chloramine-T is unity. The
results indicate first order dependence of the reaction on
both [D-threonine] and [Rh(III)]. Decreasing effect of
variation of both [OH¯] and [Cl¯] on the rate of reaction
has been observed. Addition of p-toluene sulphonamide (PTS)
and variation of ionic strength of the medium have not
affected the rate of oxidation of D-threonine, showing thus
zero effect of both ionic strength of the medium and [PTS].
The results conform to the proposed mechanism in which an
electrophilic attack at the nitrogen site in D-threonine by
the positive chlorine in the complex [RhCl3 (H2O)2-(RNHCl)]
(formed between reactive species of Rh(III) chloride and
[CAT] ) takes place in a slow and rate controlling step to
form an intermediate which finally changes into product
through a series of fast steps with regeneration of
effective species of catalyst for further recycling.
Keywords: Kinetics and Mechanism, Rh (III) catalysis,
Oxidation, D-threonine, Chloramine-T
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