Kinetic study of ruthenium(III)-catalyzed oxidation of <Emphasis Type="SmallCaps">l</Emphasis>-alanine by diperiodatoargentate(III) in aqueous alkaline medium

The kinetics of Ru(III)-catalyzed oxidation of l-alanine (Ala) by diperiodatoargentate(III) (DPA) in alkaline medium at 25 °C and a constant ionic strength of 0.90 mol dm⁻³ was studied spectrophotometrically. The products are acetaldehyde, Ag(I), ammonia and bicarbonate. The [Ala] to [DPA] stoichiometry is 1:1. The reaction is first order in both [Ru(III)] and [DPA] and has less than unit order in both [Ala] and [alkali]. Addition of periodate has a retarding effect on the reaction. The effects of added products, ionic strength and dielectric constant of the reaction medium have been investigated. The reaction proceeds via a Ru(III)–Ala complex, which further reacts with one molecule of monoperiodatoargentate(III) in the rate-determining step. The reaction constants were calculated at different temperatures and the activation parameters have been evaluated.     

Kinetics and mechanism of ruthenium(III) catalyzed oxidation of L-proline by copper(III): A free radical intervention and decarboxylation

The kinetics of ruthenium(III) catalyzed oxidation of L-proline by diperiodatocuprate(III) (DPC) in alkaline medium at constant ionic strength (0.10 mol dm⁻³) has been studied spectrophotometrically using a rapid kinetic accessory. The reaction showed first order kinetics in [DPC] and [Ru^III] and apparently less than unit order dependence each in L-proline and alkali concentrations. A mechanism involving the formation of a complex between the L-proline and the hydroxylated species of ruthenium (III) has been proposed. The active species of oxidant and catalyst were [Cu(OH)₂ (H₃IO₆)₂ (H₂IO₆)₂]⁴⁻ and [Ru (H₂O)₅OH]²⁺ respectively. The reaction constants involved in the mechanism were evaluated. The activation parameters were computed with respect to the slow step of the mechanism and discussed. The text was submitted by the authors in English.     

Ruthenium(III) catalyzed oxidation of sulfanilic acid by diperiodatocuprate(III) in aqueous alkaline medium. A kinetic and mechanistic approach

The kinetics of ruthenium(III) catalyzed oxidation of sulfanilic acid by diperiodatocuprate(III) (DPC) in alkaline medium at a constant ionic strength of (0.50 mol dm⁻³) has been studied spectrophoto-metrically. The reaction between sulfanilic acid and DPC in alkaline medium exhibits 1: 4 stoichiometry (sulfanilic acid: DPC). The reaction is first order with respect to [DPC] and [Ru^III] and has less than unit order both in [sulfanilic acid] and [alkali]. The active species of catalyst and oxidant have been identified. Intervention of free radicals was observed in the reaction. The main products were identified by spot test and IR. Probable mechanism is proposed and discussed. The reaction constants involved in the different steps of the mechanism are calculated. The activation parameters with respect to the slow step of the mechanism are computed and discussed. Thermodynamic quantities are also determined.     

Thermodynamic Quantities for the Different Steps Involved in the Oxidation of the Drug Ketorolac by Copper(III) Periodate Complex in Aqueous Alkaline Medium: A Mechanistic Approach

The oxidation of ketorolac (KET) by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at a constant ionic strength of 0.10 mol⋅dm⁻³ was studied spectrophotometrically at 298 K. The reaction is of first order in [DPC] and has less than unit order in both [KET] and [alkali], and negative fractional order in [periodate]. The oxidation reaction in alkaline medium has been shown to proceed via a DPC-ketorolac complex, which decomposes slowly in a rate determining step followed by other fast steps to give the products. The main products were identified by spot test, IR and GC-MS spectral studies. The reaction constants involved in the different steps of the mechanism were calculated at different temperatures, which yielded thermodynamic quantities for different steps of the reaction scheme. The activation parameters with respect to the slow step of the mechanism were computed and discussed; thermodynamic quantities were also determined.     

Mechanistic aspects of uncatalyzed and ruthenium(III) catalyzed oxidation of dl-ornithine by copper(III) periodate complex in aqueous alkaline medium: A comparative kinetic study

The oxidation of dl-ornithine monohydrochloride (OMH) by diperiodatocuprate(III) (DPC) has been investigated both in the absence and presence of ruthenium(III) catalyst in aqueous alkaline medium at a constant ionic strength of 0.20 mol dm⁻³ spectrophotometrically. The stiochiometry was same in both the cases, i.e., [OMH]/[DPC] = 1:4. In both the catalyzed and uncatalyzed reactions, the order of the reaction with respect to [DPC] was unity while the order with respect to [OMH] was < 1 over the concentration range studied. The rate increased with an increase in [OH⁻] and decreased with an increase in [IO₄⁻] in both cases. The order with respect to [Ru(III)] was unity. The reaction rates revealed that Ru(III) catalyzed reaction was about eight-fold faster than the uncatalyzed reaction. The oxidation products were identified by spectral analysis. Suitable mechanisms were proposed. The reaction constants involved in the different steps of the reaction mechanisms were calculated for both cases. The catalytic constant (K_C) was also calculated for catalyzed reaction at different temperatures. The activation parameters with respect to slow step of the mechanism and also the thermodynamic quantities were determined. Kinetic experiments suggest that [Cu(H₂IO₆)(H₂O)₂] is the reactive copper(III) species and [Ru(H₂O)₅OH]²⁺ is the reactive Ru(III) species.     

Oxidative degradation and deamination of atenolol by diperiodatocuprate(III) in aqueous alkaline medium: A mechanistic study

The kinetics of oxidation of atenolol (ATN) 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 ATN in alkaline medium exhibits 1:2 stoichiometry (ATN:DPC). The reaction is of first order in [DPC] and has less than unit order in both [ATN] and [alkali]. However, the order in [ATN] and [alkali] changes from first order to zero order as their concentration increase. Intervention of free radicals was observed in the reaction. Increase in periodate concentration decreases the rate. The oxidation reaction in alkaline medium has been shown to proceed via a monoperiodatocuprate(III)–ATN complex, which decomposes slowly in a rate-determining step followed by other fast steps to give the products. The main oxidative products were identified by spot test, IR, NMR and LC–ESI-MS studies. The reaction constants involved in the different steps of the mechanism are calculated. The activation parameters with respect to slow step of the mechanism are computed and discussed, and thermodynamic quantities are also determined.     

Kinetics and mechanism of Ru(III)-catalyzed oxidation of aliphatic alcohols by trichloroisocyanuric acid in HClO4 medium

The kinetics and mechanism of Ru(III)-catalyzed oxidation of some aliphatic alcohols by trichloroisocyanuric acid (TCICA) has been studied in aqueous HOAc-HClO₄ medium. The reaction is zero order in [TCICA], fractional order in [alcohol] and first order in [Ru(III)]. The reaction is insensitive towards changes in acid concentration. The rate is not affected by an increase in [Cl⁻]. The polar reaction constant (ρ*) was found to be −1.27 at 308 K. A mechanism involving complex formation between the substrate and catalyst in the fast equilibrium step followed by its decomposition in a slow step is proposed.     

Spectral and Mechanistic Investigation of the Osmium(VIII) Catalyzed Oxidation of Diclofenac Sodium by the Copper(III) Periodate Complex in Aqueous Alkaline Medium

The kinetics of the osmium(VIII) (Os(VIII)) catalyzed oxidation of diclofenac sodium (DFS) by diperiodatocuprate(III) (DPC) in aqueous alkaline medium has been studied spectrophotometrically at a constant ionic strength of 1.0 mol⋅dm⁻³. The reaction showed first order kinetics in [Os(VIII)] and [DPC] and less than unit order with respect to [DFS] and [alkali]. The rate decreased with increase in [periodate]. The reaction between DFS and DPC in alkaline medium exhibits 1:2 [DFS]:[DPC] stoichiometry. However, the order in [DFS] and [OH⁻] changes from first order to zero order as their concentration increases. Changes in the ionic strength and dielectric constant did not affect the rate of reaction. The oxidation products were identified by LC-ESI-MS, NMR, and IR spectroscopic studies. A possible mechanism is proposed. The reaction constants involved in the different steps of the mechanism were calculated. The catalytic constant (K _C) was also calculated for Os(VIII) catalysis at the studied temperatures. From plots of log ₁₀ K _C versus 1/T, values of activation parameters have been evaluated with respect to the catalytic reaction. The activation parameters with respect to the slow step of the mechanism were computed and discussed, and thermodynamic quantities were also determined. The active osmium(VIII) and copper(III) periodate species have been identified.     

Oxidation of L-phenylalanine by diperiodatoargentate(III) in aqueous alkaline medium. A Mechanistic approach

The kinetics of oxidation of L-phenylalanine (L-Phe) by diperiodatoargentate(III) (DPA) in alkaline medium at a constant ionic strength of 0.25 mol/dm⁻³ has been studied spectrophotometrically. The reaction between DPA and L-phenylalanine in alkaline medium exhibits 1: 1 stoichiometry (L-phenylalanine: DPA). The reaction shows first order in [DPA] and has less than unit order dependence each in both [L-Phe] and [Alkali] and retarding effect of [IO₄⁻] under the reaction conditions. The active species of DPA is understood to be as monoperiodatoargentate(III) (MPA). The reaction is shown to proceed via a MPA-L-Phe complex, which decomposes in a rate-determining step to give intermediates followed by a fast step to give the products. The products were identified by spot and spectroscopic studies. The reaction constants involved in the different steps of the mechanisms were calculated. The activation parameters with respect to slow step of the mechanism were computed and discussed. The thermodynamic quantities were also determined for the reaction.     

Ruthenium(III) catalysed oxidation of l-leucine by a new oxidant,diperiodatoargentate(III) in aqueous alkaline medium

The kinetics of Ru(III) catalysed oxidation of l-leucine by diperiodatoargentate(III) (DPA) in alkaline medium at 298 K and a constant ionic strength of 0.60 mol dm⁻³ was studied spectrophotometrically. The oxidation products are pentanoic acid and Ag(I). The stoichiometry is [l-leucine]:[DPA] = 1:2. The reaction is of first order in Ru(III) and [DPA] and has less than unit order in both [l-leu] and [alkali]. The oxidation reaction in alkaline medium has been shown to proceed via a Ru(III)–l-leucine complex, which further reacts with one molecule of monoperiodatoargentate(III) (MPA) in a rate determining step followed by other fast steps to give the products. The main products were identified by spot test and spectral studies. The reaction constants involved in the different steps of the mechanism are calculated. The catalytic constant (K_c) was also calculated for the Ru(III) catalysed reaction at different temperatures. From the plots of log K_c versus 1/T, values of activation parameters with respect to the catalyst have been evaluated. The activation parameters with respect to the slow step of the mechanism are computed and discussed, and thermodynamic quantities are also determined. The active species of catalyst and oxidant have been identified.     

Periodate Influencing Diperiodatocuprate(III) Oxidation of Sulfur Containing Amino Acid in Aqueous Alkaline Medium

The diperiodatocuprate(III) (DPC) oxidation of DL-methionine, a sulfur containing amino acid, was studied spectrophotometrically in alkaline solution. The reaction rate was first order in the concentration of DPC and fractional order in the concentration of DL-methionine. Increasing the OH⁻ concentration decreased the rate of reaction, whereas adding IO₄⁻ enhanced the rate. The reaction was preceded by a small initiation period of about 0.8 minutes. This initiation time decreased when the concentration of IO₄⁻ or DPC increased. Adding the reaction products did not alter the rate of reaction. A mechanism including the intervention of a DL-methionine free radical is proposed and the corresponding rate law is derived. The reaction rate constants are evaluated as well as the activation parameters.     

Oxidation of L-lysine by diperiodatocuprate (III) in aqueous alkaline medium by the stopped flow technique

The kinetics of oxidation of L-lysine by diperiodatocuprate (III) (DPC) in alkaline medium at a constant ionic strength of 0.15 mol/dm³ was studied spectrophotometrically. The reaction between DPC and L-lysine in an alkaline medium had a 1: 2 stoichiometry (L-lysine: DPC). The reaction was first order in [DPC] and less than first order in [L-lysine] and [alkali]. The addition of periodate had no effect on the rate of the reaction. The intervention of free radicals was observed in the reaction. The oxidation reaction in alkaline medium was shown to proceed via a DPC-L-lysine complex. The main products were identified by spot test and spectral studies. The reaction constants involved in different steps of the mechanism were calculated. The activation parameters with respect to the slow step of the mechanism were computed and discussed, and thermodynamic values were also determined. The article is published in the original.     

Oxidation of vanillin by diperiodatocuprate(III) in aqueous alkaline medium: A kinetic and mechanistic study by stopped flow technique

The kinetics of oxidation of vanillin (VAN) by diperiodatocuprate(III) (DPC) in alkaline medium at a constant ionic strength of 0.50 mol dm^?3 was studied spectrophotometrically. The reaction between DPC and vanillin in alkaline medium exhibits 1:2 stoichiometry (vanillin: DPC). The reaction is of first order in [DPC] and has less than unit order in both [VAN] and [alkali]. Intervention of free radicals was observed in the reaction. Increase in periodate concentration decreases the rate. The oxidation reaction in alkaline medium has been shown to proceed via a monoperiodatocuprate(III)–vanillin complex, which decomposes slowly in a rate‐determining step followed by other fast steps to give the products. The main products were identified by spot test, IR, and MS studies. The reaction constants involved in the different steps of the mechanism are calculated. The activation parameters with respect to slow step of the mechanism are computed and discussed, and thermodynamic quantities are also determined. © 2007 Wiley Periodicals, Inc. 39: 236–244, 2007     

Mechanistic investigations on the oxidation of <Emphasis Type="SmallCaps">l</Emphasis>-valine by diperiodatocuprate(III) in aqueous alkaline medium: a kinetic model

The oxidation of l-valine (l-val) by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at a constant ionic strength of 3.0 × 10⁻³ mol dm⁻³ was studied spectrophotometrically at 298 K and follows the rate law;

Kinetics and mechanism of uncatalysed and ruthenium(III)-catalysed oxidation of <Emphasis Type="SmallCaps">d</Emphasis>-panthenol by alkaline permanganate

The oxidation of d-panthenol by MnO₄ ⁻ was studied in the absence and in the presence of ruthenium(III) catalyst in alkaline medium at 298 K and at constant ionic strength of 0.50 mol dm⁻³ by spectrophotometry. The stoichiometry in both the cases was [panthenol]: [MnO₄ ⁻] = 1:4. The oxidation products were identified by IR and GC–MS. The reaction was first-order with respect to both MnO₄ ⁻ and ruthenium(III), while the orders with respect to both panthenol and alkali varied from first order to zero order as the concentrations increased. The effects of added products, ionic strength and dielectric constant were studied. The reaction constants, activation parameters and thermodynamic quantities were calculated for both the uncatalysed and catalysed reactions.     

Investigation of the mechanism of oxidation of <Emphasis Type="SmallCaps">l</Emphasis>-cystine by diperiodatoargentate(III) in aqueous alkaline medium by stopped flow technique

The kinetics of oxidation of l-cystine by diperiodatoargentate(III) (DPA) in alkaline medium at a constant ionic strength of 0.10 mol dm⁻³ was studied spectrophotometrically. The reaction exhibits a 1:2 stoichiometry (l-cys:DPA) and is first order in [DPA]. The order in both [l-cystine] and [alkali] changes from first to zero order as their concentrations increase. Added periodate retards the rate of reaction. The effects of added products have been investigated. The active species of silver(III) is identified as monoperiodatoargentate(III) (MPA). The oxidation is thought to proceed via an MPA–l-cystine complex, which decomposes in a rate-determining step to give a free radical followed by a fast step to give the products. The products were identified by spot test, IR and GC–MS. The reaction constants involved in different steps of the mechanism were evaluated. The activation parameters with respect to the slow step of the mechanism were computed and discussed.     

A kinetic and mechanistic study on oxidation of Isoniazid drug by alkaline diperiodatocuprate(III) – A free radical intervention

The kinetics of oxidation of isoniazid (INH) by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at a constant ionic strength of 0.05 mol dm⁻³ has been studied spectrophotometrically. The reaction showed first order kinetics both in [DPC] and [INH] and negative less than unit order, both in alkali and periodate concentrations under the experimental conditions. Intervention of free radicals was observed in the reaction. Products of the reaction, isonicotinic acid and copper(II) have no effect on the rate of reaction. Ionic strength and dielectric constant did not affect the rate of reaction. Based on the observed orders and experimental evidences, a mechanism involving the monoperiodatocuprate(III) (MPC) as the reactive oxidant species has been proposed. The main products were identified by I.R, N.M.R. and GC-MS spectral studies. The reaction constants involved in the mechanism were evaluated. Investigations at different temperatures allowed the determination of the activation parameters with respect to the slow step of proposed mechanism. The mechanism proposed and the derived rate laws are consistent with the observed kinetics.     

Kinetic study of the ruthenium(III)-catalyzed oxidation of glycine by <Emphasis Type="Italic">N</Emphasis>-bromophthalimide in acidic medium

The kinetics of ruthenium(III) chloride-catalyzed oxidation of glycine by N–bromophthalimide (NBP) was studied in aqueous perchloric acid at 35 °C. The results showed first- and zero-order behavior with respect to NBP and Gly, respectively. Ru(III) showed a catalytic effect on the reaction which followed first-order kinetics with respect to [Ru(III)] at a low concentration range and tended to zero order at high concentration range. The rates decreased with increase in the proton concentration, while chloride positively influenced the rate of the reaction. Two moles of NBP were required to oxidize one mole of Gly, and the products were identified as phthalimide (NHP), HCN, CO₂, and Br⁻. Neither added NHP nor Br⁻ influenced the reaction rate. Ionic strength and dielectric constant of the medium had no significant effect on the rate. Activation parameters were determined by studying the reaction at different temperatures. A reaction scheme of the catalytic oxidation is proposed.     

Kinetics and mechanism of ruthenium(III) catalyzed oxidation of chloromphenicol—An antibiotic drug by diperiodatocuprate(III) in aqueous alkaline medium

The kinetics of ruthenium(III) catalyzed oxidation of chloramphenicol (CHP) by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at a constant ionic strength of 0.1 mol l⁻¹ was studied spectrophotometrically. The reaction between DPC and CHP in alkaline medium exhibits 1: 2 stoichiometry (CHP: DPC). The main oxidation products were identified by spot test, IR, NMR, and GC-MS spectral studies. The reaction is first order with respect to ruthenium(III) and DPC concentrations. The order with respect to chloramphenicol concentration varies from first order to zero order as the chloramphenicol concentration increases. As the alkali concentration increases the reaction rate increases with fractional order dependence on alkali concentration. Increase in periodate concentration decreases the rate. A mechanism adequately describing the observed regularities is proposed. The reaction constants involved in the different steps of the mechanism were calculated. The activation parameters with respect to limiting step of the mechanism are computed and discussed. Thermodynamic quantities are determined.