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|Title:||Mechanistic studies of aquachlororhodium(III) catalysis in potassium iodate oxidation of 1,2-propanediol in acidic medium: A kinetic approach|
Singh, Aniruddh Kumar
|Abstract:||The kinetics of homogeneously Rh(III) catalysed oxidation of 1, 2-propanediol by acidic solution of potassium iodate at constant ionic strength of the medium has been investigated at 308 K. The reaction follows complex kinetics, being first order in [KIO<sub>3</sub>], zero order in 1, 2-propanediol and inverse fractional order in both [H<sup>+</sup>] and [Cl<sup>¯</sup>]. The first order rate constant increases linearly with increase in [Rh(III)] in its lower concentration range but as the concentration of Rh(III) is increased towards the higher range, the rate constant becomes almost constant, indicating positive fractional order in [Rh(III)]. Variation of ionic strength of the medium and successive addition of mercuric acetate (used as I<sup>¯</sup> ions scavenger) has a positive effect on the rate of the reaction. IO<sub>3</sub><sup>¯</sup> and [RhCl<sub>5</sub>(H<sub>2</sub>O)]<sup>-2</sup> have been postulated as the reactive species of KIO<sub>3</sub> and Rh(III), respectively. Activation parameters for the slow and rate determining step of the proposed mechanism, which involves the formation of the most activated complex, [Cl<sub>5</sub>Rh(HO→Hg)]<sup>¯</sup>, prior to the slowest step, have been obtained from rate measurements at 30, 35, 40 and 45 °C. The rate law conforming to the observed kinetic results has been derived as <img src='http://www.niscair.res.in/jinfo/IJCA/IJCA 50A(5) 650-657-image.gif'>. The main oxidation products have been identified as acetic acid and formic acid|
|Appears in Collections:||IJC-A Vol.50A(05) [May 2011]|
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