Abstract
The kinetics of oxidation of L‐proline by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at a constant ionic strength of 0.10 mol dm‐3 was studied spectrophotometrically. The reaction between DPC and L‐proline in alkaline medium exhibits 2:1 stoichiometry (DPC: L‐Proline). The reaction is of first order in [DPC], less than unit order in [L‐proline] and [alkali]. Periodate has no effect on the rate of reaction. The reaction rate increases with increase in ionic strength and decrease in solvent polarity of the medium. Effect of added products and ionic strength of the reaction medium have been investigated. The main products were identified by spot test and I.R spectra. A mechanism involving the DPC as the reactive species of the oxidant and a complex formation with L‐proline has been proposed. The reaction constants involved in the different steps of mechanism are calculated. The activation parameters with respect to slow step of the mechanism are computed and discussed and thermodynamic quantities are also calculated.
Highlights
The kinetics of oxidation of L-proline by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at a constant ionic strength of 0.10 mol dm-3 was studied spectrophotometrically
Stoichiometry and product analysis Different sets of reaction mixtures containing excess DPC than L-proline with constant OH- and KNO3 were kept for 6 hrs in closed vessel under nitrogen atmosphere
The results indicated 2:1 stoichiometry as given in Eq(1)
Summary
The kinetics of oxidation of L-proline by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at a constant ionic strength of 0.10 mol dm-3 was studied spectrophotometrically. Effect of added products and ionic strength of the reaction medium have been investigated. A mechanism involving the DPC as the reactive species of the oxidant and a complex formation with L-proline has been proposed. The reaction constants involved in the different steps of mechanism are calculated. Diperiodatocuprate (III) (DPC) is a versatile one-electron oxidant for various organic compounds in alkaline medium and its use as an analytical reagent is well recognized and used in estimation of amino acids[3]. Copper (III) is shown to be an intermediate in the Cu(II) catalysed oxidation of amino acids by peroxdisulphate[5]. The kinetic measurements were performed on a Peltier Accessory (temperature control) attached Varian CARY 50 Bio uv – vis spectrophotometer and IR studies were performed by Nicolet Impact – 410 FTIR
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