Deamination and decarboxylation in the chromium(III)-catalysed oxidation of L-valine by alkaline permanganate and analysis of chromium(III) in microscopic amounts by a kinetic method

The kinetics of Cr^III-catalysed oxidation of L-valine by permanganate in alkaline medium at a constant ionic strength has been studied spectrophotometrically. The reaction between permanganate and L-valine in alkaline medium exhibits 2:1 stoichiometry (KMnO₄:l-valine). The reaction shows first order dependence on [permanganate] and [chromium(III)], and less than unit order dependence each in [L-valine] and alkali concentrations under the experimental conditions. However the order in [L-valine] and [alkali] changes from first order to zero order as the concentrations change from lower to higher respectively. The results suggest the formation of a complex between L-valine and the hydroxylated species of Cr^III. The complex reacts further with 1 mol of alkaline permanganate species in a rate-determining step, resulting in the formation of a free radical, which again reacts with 1 mol of alkaline permanganate species in a subsequent fast step to yield the products. The reaction constants involved in the mechanism were evaluated. The activation parameters with respect to the slow step of the mechanism were obtained and discussed. The title reaction has been utilised to analyse chromium(III) in the 26.0 ng cm^–3–1.0 g cm^–3 range.     

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 of oxidation of <Emphasis Type="SmallCaps">l</Emphasis>-lysine by the analytical reagent diperiodatoargentate(III) in aqueous alkaline medium

The kinetics of oxidation of l-lysine by diperiodatoargentate(III) (DPA) in aqueous alkaline medium at a constant ionic strength of 0.50 mol dm⁻³ was studied spectrophotometrically. The oxidation products are aldehyde, 5-aminopentanal and Ag(I). The main products were identified by spot test, IR and GC-MS. The stoichiometry is [l-lysine]:[DPA] = 1:1. The reaction is first order with respect to diperiodatoargentate(III) concentrations, whereas the order with respect to l-lysine and alkali concentrations changes from first order to zero order as the l-lysine and alkali concentrations are increased. The effects of added products, periodate, ionic strength, and dielectric constant of the reaction medium were investigated. Based on the experimental results, a mechanism involving complex formation between DPA species and l-lysine is proposed. The reaction constants involved in the mechanism were evaluated. The activation parameters with respect to the slow step of the mechanism were determined and discussed.     

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.     

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.     

Kinetics and mechanism of <Emphasis Type="Italic">L</Emphasis>-isoleucine oxidation by alkaline diperiodatoargentate(III)

The oxidation of L-isoleucine by alkaline diperiodatoargentate(III) (DPA) at 298 K and a constant ionic strength of 0.80 mol dm⁻³ was studied spectrophotometrically. The stoichiometry is [L-isoleucine]: [DPA] = 1:2. The reaction is first order in [DPA] and has less than unit order in both [L-isoleucine] and [alkali] and retarding effect in The oxidation reaction in alkaline medium has been shown to proceed via a L-isoleucine–DPA complex, which further reacts with one molecule of DPA in a rate determining step followed by other fast steps to give the products. Spot test and IR were used to identify the main products. 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, and thermodynamic quantities are also determined. The probable active species of oxidant have been identified. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

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.     

Mechanistic investigations of ruthenium(III) catalyzed oxidation of pentoxifylline by copper(III) periodate complex in aqueous alkaline medium

Abstract  

The kinetics of the oxidation of ruthenium(III)-catalyzed oxidation of pentoxifylline (PTX) by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at a constant ionic strength of 0.30 mol dm⁻³ was studied spectrophotometrically. The reaction between PTX and DPC in alkaline medium in the presence of Ru(III) exhibits 1:2 stoichiometry (PTX:DPC). The reaction was of first order in DPC, less than the unit order in [PTX] and [OH⁻] and negative fractional order in [IO₄ ⁻]. The order in [Ru(III)] was unity. Intervention of free radicals was observed in the reaction. The main products were identified by TLC and spectral studies including LC-MS. The oxidation reaction in alkaline medium has been shown to proceed via a Ru(III)-PTX complex, which reacts with monoperiodatocuprate(III) to decompose in a rate determining step followed by a fast step to give the products. 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 quantities were also determined. The active species of catalyst and oxidant have been identified.     

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.     

Aquachlororuthenium(III) complex catalysis in the oxidation of malonic and methylmalonic acids by bromate in perchloric acid medium. Study of induction period and evaluation of individual kinetic parameters

The kinetics and mechanism of an aquachlororuthenium(III) complex catalyzed oxidation of malonic and methylmalonic acids by bromate in aqueous acetic acid medium containing perchloric acid and mercury(II) is reported here. The reaction shows an induction period (τ₀), whose duration is inversely proportional to [substrate]₀ and [catalyst]₀, and temperature; however, independent of [bromate]₀. After induction, the reaction exhibits first order each in [bromate] and [catalyst], less than unit order in [substrate] and an inverse fractional order in [HClO₄]. The reaction also shows an inverse solvent isotope effect The observed rate law is interpreted by a mechanism involving the oxidation of Ru^III to Ru^V by Br^V (K _f), followed by complex formation (K _c) between the Ru^V and enol form (K _en) of the substrate in 1:1 ratio, which decomposes (kd) into products in the rate-determining step with regeneration of Ru^III. The observed induction period is interpreted as the time-lag in building-up of the reactive intermediate(s). The reaction constants (K _f, K _c, K _en and kd) involved in the mechanism proposed have been evaluated and τ₀ has been correlated in terms of initial concentrations of substrate and catalyst as: 1/τ₀ = Q(X-1)[Sa]₀ ^(x-1) = Q′(Z-1)[Ru(III)]₀ ^(z-1).     

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 the oxidation of chromium(III)–dipicolinic acid complex by N-bromosuccinimide

The kinetics of oxidation of the chromium(III)–dipicolinic acid complex [Cr^III(DPA)₂(H₂O)₂]^– by N-bromosuccinimide (NBS) in aqueous solution to Cr^VI have been studied spectrophotometrically over the 20–40 °C range. The reaction is first order with respect to both [NBS] and [Cr^III], and increases with pH over the 5.92–6.93 range. Thermodynamic activation parameters were calculated. It is proposed that electron transfer proceeds through an inner-sphere mechanism via coordination of [NBS] to chromium(III).     

Mechanistic aspects of the reduction of ruthenium(III) catalyzed

The kinetics of Ru_III catalyzed reduction of hexacyanoferrate(III) [Fe(CN)₆]^3–, by atenolol in alkaline medium at constant ionic strength (0.80 mol dm^–3) has been studied spectrophotometrically, using a rapid kinetic accessory. The reaction between atenolol and [Fe(CN)₆]^3– in alkaline medium exhibits 1:2 stoichiometry [atenolol:Fe(CN)₆ ^3–]. The reaction showed first order kinetics in [Fe(CN)₆]^3– concentration and apparent less than unit order dependence, each in atenolol and alkali concentrations. Effect of added products, ionic strength and dielectric constant of the reaction medium have been investigated. A retarding effect was observed by one of the products i.e., hexacyanoferrate(II). The main products were identified by i.r., n.m.r., fluorimetric and mass spectral studies. A mechanism involving the formation of a complex between the atenolol and the hydroxylated species of ruthenium(III) has been proposed. The active species of oxidant and catalyst were [Fe(CN)₆]^3–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.     

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.     

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 and Spectral Studies of the Ruthenium(III) Catalysed Oxidation of Sulfanilic Acid by Alkaline Hexacyanoferrate(III)

Summary. The kinetics of ruthenium(III) catalysed oxidation of sulfanilic acid (p-aminobenzenesulfonic acid) by hexacyanoferrate(III) in alkaline medium at a constant ionic strength of 2.5mol·dm^–3 has been studied spectrophotometrically using a rapid kinetic accessory. The reaction exhibits 2:8 stoichiometry (SNA:HCF(III)). The reaction showed first order kinetics in [hexacyanoferrate(III)] and [ruthenium(III)] and apparent less than unit order in both sulfanilic acid and alkali concentrations. The reaction rate increases with increasing ionic strength but the relative permittivity (_T) of the medium has a negligible effect on the rate of the reaction. Initial addition of reaction products did not affect the rate significantly. A mechanism involving the formation of a complex between sulfanilic acid and hydroxylated species of ruthenium(III) has been proposed. The active species of HCF(III) and ruthenium(III) are understood as [Fe(CN)₆^3–] and [Ru(H₂O)₅OH]²⁺, respectively. The main products were identified by IR, NMR, and mass spectral studies. The reaction constants involved in the different steps of mechanism are calculated. The activation parameters with respect to the slow step of the mechanism are computed and discussed and thermodynamic quantities are also calculated.     

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.     

三价银配合物氧化1,4-丁二胺的反应动力学及机理研究

碱性介质中, 在离子强度不变的条件下, 用广度法研究了三价银配合物氧化1,4-丁二胺的动力学及机理. 反应对三价银配合物和都是一级反应, 二级反应速率常数(k’) 随碱浓度的增大而增大,随糕碘酸根离子浓度的增大而减小. 据此提出了适合此反应的反应机理, 并计算得到了反应的热力学参数.     

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.