Ruthenium(III) catalysed and uncatalysed oxidative mechanisms of methylxanthine drug theophylline by copper(III) periodate complex in alkali media: a comparative approach

Abstract

The kinetics of oxidation of methylxanthine drug, theophylline (TP), by diperiodatocuprate(III) (DPC) has been investigated in the absence and presence of ruthenium(III) (Ru(III)) as homogeneous catalyst in alkaline medium at a constant ionic strength of 0.21 mol dm−3 spectrophotometrically. The reaction exhibits 1:4 stoichiometry ([TP] : [DPC]) in both the cases. The order of the reaction with respect to [DPC] was unity, while the order with respect to [TP] was less than unity over the concentration range studied in both the cases. The rate was increased with an increase in [OH−] and decreased with an increase in [IO4−]. The order with respect to [Ru(III)] was unity. The ionic strength and dielectic constant of the medium did not affect the rate significantly. The main product 1‐methyl‐(3‐N‐formyl)‐2,4‐purinodione was identified by spot tests, Fourier transform infrared spectroscopy and liquid chromatography–mass spectrometry spectral studies. Based on the experimental results, the possible mechanisms were proposed. The reaction constants involved in the different steps of the mechanisms were evaluated. The catalytic constant (Kc) was also calculated for Ru(III) catalysis at different temperatures. The activation parameters with respect to the catalyst and slow step of the mechanisms were computed, and thermodynamic quantities were determined. Kinetic studies suggest that the active species of DPC and Ru(III) are found to be [Cu(H2IO6)(H2O)2] and [Ru(H2O)5OH]2+, respectively. Copyright © 2015 John Wiley & Sons, Ltd.

Autocatalyzed oxidation of d‐glucitol by alkaline copper (III) periodate complex: A kinetic and mechanistic approach

“…It was observed that the reaction exhibited an order of negative fraction with respect to [IO 4 − ], less than unit order in DG and alkali concentrations (Table 1). In view of the retarding effect of periodate, the active species of DPC have been proposed as [Cu(H 2 IO 6 )(H 2 O) 2 ], which was also observed in earlier report, [ 25 ] and the mechanism befitting the obtained results was proposed (Scheme 1). In aqueous alkaline medium, a diaquomonoperiodato copper (III) complex (MPC) (in Equation 5) was produced due to substitution of bidentate ligand [H 3 IO 6 2− ] of DPC by water molecules, and its formation was important in the present study.…”

“…Thus, [Cu(H 3 IO 6 ) (H 2 IO 6 )] 2− is the soluble copper (III) periodate complex in the employed pH conditions, also supported by the earlier work. [ 25 ]

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A Spectroscopic Approach on Permanganate Oxidation of 1-[(4-Chlorophenyl)methyl]piperidin-4-amine in Presence of Ruthenium(III) Catalyst with DFT Analysis on Reaction Mechanism Pathway

“…The presence of hydrated form of ruthenium(III) chloride in alkaline media as [Ru(H2O)6] 3+ have been reported [24]. The oxidation reaction between CMP and permanganate in existance of Ru(III) chloride has stoichiometry of 1:4 with unit order dependence on permangate and Ru(III) and fraction order dependance on base and CMP, which indicates the formation of MnO4•OH 2-, it is further supported by the plot [Ru(III)]/kobs vs. 1/[OH -] with positive intercept.…”