Effect of Anionic Surfactant on the Oxidation of DL-Aspartic Acid by N-Bromophthalimide: A Kinetic Study

The kinetics of oxidation of DL-Aspartic acid (Asp) by N-bromophthalimide (NBP) was studied in the presence of sodium dodecyl sulfate (SDS) in acidic medium at 308 K. The rate of reaction was found to have first-order dependence on [NBP], fractional order dependence on [Asp] and inverse fractional order dependence on [H⁺]. The addition of reduced product of the oxidant, that is, [Phthalimide] has decreased the rate of reaction. The rate of reaction increased with increase in inorganic salts concentration, whereas a change in [Cl^?], ionic strength of the medium and [Hg(OAc)₂] had no effect on the oxidation velocity. The rate of reaction decreased with a decrease in dielectric constant of the medium. COOH-CH₂-CN was identified as the main oxidation product of the reactions. The various activation parameters have been computed. A suitable reaction mechanism consistent with the experimental findings has been proposed. The micelle-binding constant has been calculated.     

Kinetic Study of Oxidation of DL-Serine by N-Bromophthalimide in the Presence of Sodium Dodecyl Sulfate

The kinetics of oxidation of DL-serine (Ser) by N-bromophthalimide (NBP) was studied in the presence of an anionic surfactant, sodium dodecyl sulfate, in acidic medium at 308 K. The rate of reaction was found to have first-order dependence on [NBP], fractional order dependence on [Ser] and inverse fractional order dependence on [H⁺]. The addition of reduced product of the oxidant [Phthalimide] and [Hg(OAc)₂] has no effect on the rate of reaction. The change in ionic strength of the medium had no effect on oxidation velocity. The rate of reaction increased with increasing [Br^?] and decreased with increasing [Cl^?]. The rate of reaction decreased with decrease in dielectric constant of the medium. OHCH₂CN was identified as the main oxidation product of the reactions. The various activation parameters have been computed. A suitable mechanism consistent with the experimental findings has been proposed. The micelle-binding constant has been calculated.     

Kinetics and mechanism of oxidation of L-Alanine by <Emphasis Type="Italic">N</Emphasis>-bromophthalimide in the presence of sodium dodecyl sulfate

The kinetics of oxidation of L-Alanine (Ala) by N-bromophthalimide (NBP) was studied in the presence of an anionic surfactant, sodium dodecyl sulfate, in acidic medium at 308 K. The rate of reaction was found to have first-order dependence on [NBP], fractional order dependence on [Ala] and inverse fractional order dependence on [H⁺]. The addition of reduced product of the oxidant [Phthalimide] has decreased the rate of reaction. The rate of reaction increased with increase in inorganic salts concentration i.e., [Cl⁻] and [Br⁻], whereas a change in ionic strength of the medium and [Hg(OAc)₂] had no effect on oxidation velocity. The rate of reaction decreased with a decrease in dielectric constant of the medium. CH₃CN was identified as the main oxidation product of the reaction. The various activation parameters have been computed and suitable mechanism consistent with the experimental findings has also been proposed. The micelle-binding constant has been calculated. Published in Russian in Kinetika i Kataliz, 2009, Vol. 50, No. 3, pp. 386–396. The article is published in the original.     

Effect of Cationic Micelle on the Kinetics of Oxidation of Citric Acid by N-Bromophthalimide in Acidic Medium

Kinetics of the oxidation of citric acid (CA) by N-bromophthalimide (NBP) has been studied in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB) at 35°C. The CMC value is lower than those given in the literature for aqueous solutions of CTAB without added electrolyte. The reaction is strongly catalyzed by cationic micelle, CTAB with a progressive increase in CTAB concentration the reaction rate increased, at higher concentration constancy in the rate constant was observed. The reaction follows first and fractional order kinetics in NBP and citric acid, respectively. The reaction follows inverse fractional order with respect to perchloric acid. The Arrhenius equation is found to be valid for the reaction. A detailed mechanism with the associated reaction kinetics is discussed. The catalytic role of CTAB micelles is discussed in terms of the Menger and Portnoy model.     

Kinetic studies on the mechanism of the relative catalytic activities of surfactants in the oxidation of amino-acids by chloramine-T

The kinetics of oxidation of amino-acids by chloramine-T in the presence of two different surfactants (cationic and anionic surfactants) in acidic medium has been studied. The kinetic results show that the reaction is fractional and first order with respect to substrate and oxidant respectively. The influence of halides, ionic strength and solvent on the rate has been studied. The effect of surfactants on the reaction show that the reaction velocity is highly sensitive to the variation of surfactant concentration. The micelle-substrate binding constant (K) and co-operativity index have been calculated indicating the stability of the catalyst substrate micelles (complex) so formed. A probable reaction path has been suggested and discussed in the light of various experimental results and findings.     

Kinetics of oxidation of pantothenic acid by chloramine‐T in perchloric acid and in alkaline medium catalyzed by OsO4: A mechanistic approach

Kinetics of oxidation of pantothenic acid (PA) by sodium N‐chloro‐p‐toluenesulfonamide or chloramine‐T (CAT) in the presence of HClO₄ and NaOH (catalyzed by OsO₄) has been investigated at 313 K. The stoichiometry and oxidation products are same in both media; however, their kinetic patterns were found to be different. In acid medium, the rate shows first‐order dependence on [CAT]_o, fractional‐order dependence on [PA]_o, and inverse fractional‐order on [H⁺]. In alkaline medium, the rate shows first‐order dependence each on [CAT]_o and [PA]_o and fractional‐order dependence on each of [OH^?] and [OsO₄]. Effects of added p‐toluenesulfonamide and halide ions, varying ionic strength, and dielectric constant of medium as well as solvent isotope on the rate of reaction have been investigated. Activation parameters were evaluated, and the reaction constants involved in the mechanisms have been computed. The proposed mechanisms and the derived rate laws are consistent with the observed kinetics. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 201–210, 2005     

Kinetics and Mechanism of Cetyltrimethylammonium Bromide Catalyzed N-Bromosuccinimide Oxidation of D-Mannose in Acidic Medium

The kinetics and mechanism of N-bromosuccinimide (NBS) oxidation of D-mannose in the absence and presence of cetyltrimethylammonium bromide (CTAB) in acidic media have been studied under the condition [D-mannose]_T ? [NBS]_T at 40°C. Under the kinetic conditions, both the slower uncatalyzed and faster catalyzed paths go on. Both the paths show the fractional and first order dependence on [D-mannose] and [NBS]_T, respectively. The rate decreased with increase in acidity. Neither succinimide (NHS) nor Hg(II) influenced the reaction rate. Activation parameters of the reactions were determined by studying the reaction at different temperatures (30–50°C). The influence of salts on the reaction rate was also studied. CTAB accelerates the reactions and the observed effects have been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. In the reaction, approximately 1 mole of NBS oxidized one mole of D-mannose. A reaction scheme of the oxidation of D-mannose by NBS was found to be in consistent with the rate law and the reaction stoichiometry.     

Synthesis,kinetics, and mechanism of bromophenols by N‐bromophthalimide in aqueous acetic acid

The kinetics and mechanism of bromination of phenol and its substituents, viz. 4‐chlorophenol, 4‐bromophenol, 4‐methylphenol, and 4‐methoxyphenol by N‐bromophthalimide (NBP) in the presence of mercuric acetate in the temperature range of 303–318 K in aqueous acetic acid medium have been investigated. The reaction follows first‐order dependence on [NBP] and fractional order dependence of rate on [Phenol]. The activation parameters have been evaluated, and based on the observed kinetic results the probable mechanism has been proposed. Observed kinetic features and Hammett's reaction constant (ρ) suggests that bromination occurs through electrophilic substitution of bromonium ion (Br⁺) into the aromatic ring in the transition state. Large negative entropy of activation values probably suggests the rigid nature of transition state.     

Effect of Cationic Micellar Aggregates on the Kinetics of Dextrose Oxidation by N-Bromophthalimide

The effect of cationic micelles of Cetyltrimethyl ammonium bromide (CTAB) on the kinetics of oxidation of dextrose by N-Bromophthalimide were studied at 40°C. The reaction follows fractional-order and first order kinetics, with respect to [dextrose] and [NBP], respectively. CTAB strongly catalyze the reaction, and typical k_obs and [CTAB] profile was observed, that is, with a progressive increase in [CTAB], the reaction rate increased, reaches a maximum value then decreased. Results are treated quantitatively in terms of Berezin's Model, which is applicable to bimolecular micellar catalyzed reaction. There is a negative effect of mercuric acetate and phthalimide. The influence of salts on the reaction rates has also been seen. The activation parameters as well as other parameters were calculated and suitable mechanism consistent with the experimental findings has been proposed.     

Kinetics and mechanistic aspects on electron‐transfer process for permanganate oxidation of poly(ethylene glycol) in aqueous acidic solutions in the presence and absence of Ru(III) catalyst

The kinetics and mechanism of oxidation of poly(ethylene glycol) (PEG) by the permanganate ion as a multiequivalent oxidant in aqueous perchlorate solutions at an ionic strength of 2.0 mol dm⁻³ has been investigated spectrophotometrically. The reaction kinetics was found to be of complex in nature. The pseudo–first‐order plots showed curves of inverted S‐shape, consisting of two distinct stages throughout the entire course of reaction. The first stage was relatively slow, followed by a fast reaction rate at longer time periods. The first‐order dependence in [MnO₄⁻], fractional first‐order dependence in [H⁺], and fractional first‐order kinetics in the PEG concentration for the first stage have been revealed in the absence of the Ru(III) catalyst. The influence of the Ru(III) catalyst on the oxidation kinetics has been examined. The oxidation was found to be catalyzed by the added Ru(III) catalyst. The First‐order dependence on the catalyst and zero order with respect to the oxidant concentrations have been observed. The kinetic parameters have been evaluated, and a tentative reaction mechanism consistent with the kinetic results is suggested and discussed.     

Oxidation of alcohols by N-chlorosuccinimide—a kinetic study

The kinetics of oxidation of alcohols by N-chlorosuccinimide (NCS) have been studied. The independence of rate on the concentration and structure of alcohol and the fractional order dependence on concentrations of added H⁺ and Cl^? suggest that the reaction proceeds through the formation of Cl₂ generated in a steady concentration in a slow step followed by a rapid uptake of the alcohol. A rate expression for the observed kinetics has been suggested. This behaviour is contrasted with that of an analogous system viz, NBS and alcohol and is also compared with the Orton rearrangement.     

Kinetics and mechanism of oxidation of β-Alanine by <Emphasis Type="Italic">N</Emphasis>-bromophthalimide in the presence of Ru(III) chloride as homogenous catalyst in acidic medium

The kinetics of Ru(III) chloride-catalyzed oxidation of β-Alanine (NH₃ ⁺CH₂CH₂COOH, β-Ala) by N–bromophthalimide (NBP) in aqueous perchloric acid medium was studied at 35 °C. The rate law followed a first-order and zero-order dependence with respect to [NBP] and [β-Ala], respectively. The reaction followed first-order kinetics with respect to [Ru(III)] chloride at a range of low concentrations while the order changed from first- to zero-order at high concentration of [Ru(III)] chloride; demonstrating the catalytic effect for the oxidation of β-Ala by NBP. The rate decreased with increase in acidity. Chloride ions positively influenced the rate of the reaction. Neither phthalimide (NHP) nor Hg(II) influenced the reaction rate. Ionic strength (I) and dielectric constant (D) of the medium had no significant effect on the rate. Activation parameters of the reactions were determined by studying the reaction at different temperatures (30–50 °C). The colorimetric, FTIR, and GC-MS techniques were used to identify methyl cyanide (CH₃CN) and CO₂ as products of the reaction. In the reaction, approximately 2.3 moles of NBP oxidized one mole of β-Ala. A reaction scheme of the oxidation of β-Ala by NBP in the presence of Ru(III) chloride was found to be in consistent with the rate law and the reaction stoichiometry.     

Kinetic study of oxidation of galactose by N-bromo phthalimide in the presence of cationic micelle in acidic medium

The kinetics of micellar catalyzed oxidation of galactose by N-bromophthalimide was studied in the presence of acidic medium at 308?K. The oxidation reaction exhibits first-order kinetics with respect to oxidant (N-bromophthalimide), fractional order with respect to substrate (galactose) and positive fractional order with respect to HClO₄ on the rate of reaction. The rate of the reaction increased with decreasing the dielectric constant of the medium. With a progressive increase in the concentration of CTAB, the rate of reaction increased and after reaching peak k _obs, decreased at higher concentrations of CTAB. There catalytic roles are best explained by Berezin??s model. The influence of salts on the reaction rate was also studied. The various activation parameters have been calculated. The rate constant and binding constant with the surfactant have also been evaluated. A suitable mechanism consistent with the experimental findings has been proposed.     

Oxidative decolorization of indigo caramine dye with chloramine-T catalyzed by cobalt(II)

Decolorization of indigo caramine dye by oxidation process using chloramine-T as oxidant and Co(II) as catalyst in acidic buffer media, pH 5.8 has been kinetically studied at 300 K. Decolorization of indigo caramine dye was followed spectrophotometrically. Decolorization and oxidation led to a decrease in Chemical Oxygen Demand of the dye. The Co(II)-catalyzed reaction shows first-order dependence of the rate on chloramine-T and indigo caramine concentrations. It also shows fractional order dependence on [Co(II)] and [H⁺]. Addition of halide ions or reduction product of chloramine-T toluenesulfonamide, and variation of ionic strength and dielectric constant of the medium do not have any significant effect on the reaction rate. Activation parameters are evaluated from the Arrhenius plot, and a mechanism is proposed for the reaction.     

Kinetic study of 2‐propanol and benzyl alcohol oxidation by alkaline hexacyanoferrate(III) catalyzed by a terpyridyl ruthenium complex

The complex (Trpy)RuCl₃ (Trpy = 2,2′:6′,2″‐terpyridine) reacts with alkaline hexacyanoferrate(III) to form a terpyridyl ruthenium(IV)‐oxo complex that catalyzes the oxidation of 2‐propanol and benzyl alcohol by alkaline hexacyanoferrate(III). The reaction kinetics of this catalytic oxidation have been studied photometrically. The reaction rate shows a first‐order dependence on [RU(IV)], a zero‐order dependence on [hexacyanoferrate(III)], a fractional order in [substrate], and a fractional inverse order in [HO⁻]. The kinetic data suggest a reaction mechanism in which the catalytic species and its protonated form oxidize the uncoordinated alcohol in parallel slow steps. Isotope effects, substituent effects, and product studies suggest that both species oxidize alcohol through similar pericyclic processes. The reduced catalytic intermediates react rapidly with hexacyanoferrate(III) and hydroxide to reform the unprotonated catalytic species. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 760–770, 2000     

Kinetics and Mechanism of the Oxidation of Vanillin by Hexacyanoferrate(III) in Aqueous Alkaline Medium

The title reaction was investigated in aqueous alkaline medium. A first-order dependence in hexacyanoferrate(III) concentration and a fractional order in both vanillin and alkali were obtained at the concentrations studied. The added product, hexacyanoferrate(II), had a retarding effect on the rate of reaction. Ionic strength and dielectric constant of the reaction medium have little effect on the reaction rate. The effect of temperature on the rate of reaction has also been studied and activation parameters have been evaluated. A mechanism based on the experimental results is proposed and the rate law is derived. The reaction constants are calculated and used to regenerate the k_obs values, which are compared with the experimental values.     

Micellar catalysis on 1,10-phenanthroline promoted hexavalent chromium oxidation of ethanol

The kinetics and mechanism of Cr(VI) oxidation of ethanol in the presence and absence of 1,10-phenanthroline in aqueous acid media have been carried out. Monomeric species of Cr(VI) are kinetically active in the absence of phen, while in the phen catalyzed path, the Cr(VI)-phen complex has been suggested as the active oxidant. In the catalyzed path, the Cr(VI)-phen complex participates in the oxidation of ethanol and ultimately is converted into the Cr(III)-phen complex. In the uncatalyzed path, the Cr(VI)-substrate ester experiences an acid catalyzed redox decomposition in the rate-determining step. The uncatalyzed path shows a second-order dependence on [H⁺], while the phen catalyzed path shows a first-order dependence on [H⁺]. Both the uncatalyzed and phen-catalyzed paths show first-order dependence on [ethanol]_T and [Cr(VI)]_T. The phen-catalyzed path is first order in [phen]_T. These observations remain unaltered in the presence of externally added surfactants. CPC inhibits the reactions while SDS catalyzes the reactions. The observed miceller effects have been explained by considering partitioning of the reactants between the miceller and aqueous phase.     

Ruthenium(III)-catalyzed and uncatalyzed kinetic studies on the oxidation of sulfanilic acid by chloramine-T in perchloric acid medium: a mechanistic approach

The kinetics of the oxidation of sulfanilic acid (SAA) by sodium N-chloro-p-toluenesulfonamide (CAT) in the presence and absence of ruthenium(III) chloride have been investigated at 303 K in perchloric acid medium. The reaction shows a first-order dependence on [CAT]_o and a non-linear dependence on both [SAA]_o and [HClO₄] for both the ruthenium(III)-catalyzed and uncatalyzed reactions. The order with respect to [Ru^III] is unity. The effects of added p-toluenesulfonamide, halide, ionic strength, and dielectric constant have been studied. Activation parameters have been evaluated. The rate of the reaction increases in the D₂O medium. The stoichiometry of the reaction was found to be 1:1 and the oxidation product of SAA was identified as N-hydroxyaminobenzene-4-sulfonic acid. The ruthenium(III)-catalyzed reactions are about four-fold faster than the uncatalyzed reactions. The protonated conjugate acid (CH₃C₆H₄SO₂NH₂Cl⁺) is postulated as the reactive oxidizing species in both the cases.     

Kinetics and mechanism of oxidation of aspirin by bromamine-T,N-bromosuccinimide,and N-bromophthalimide

The kinetics of the oxidation of aspirin (ASP) by bromamine-T (BAT), N-bromosuccinimide (NBS), and N-bromophthalimide (NBP) has been studied in aqueous perchloric acid at 303 K. The oxidation reaction follows identical kinetics with first-order in [oxidant], fractional-order in [ASP], and inverse fractional-order in [H⁺]. Under identical experimental conditions the extent of oxidation with different oxidizing agents is in the order: NBS>BAT>NBP. The rate decreased with decreasing dielectric constant of the medium. The variation of ionic strength and the addition of the reaction products and halide ions had no significant effect on the reaction rate. The solvent isotope effect was studied using D₂O. Kinetic parameters were evaluated by studying the reaction at different temperatures. The reaction products were identified by GC–MS. The proposed reaction mechanism and the derived rate law are consistent with the observed kinetic data. Formation and decomposition constants for ASP-oxidant complexes have been evaluated. Decarboxylation, bromination, and loss of acetic acid gave 2,4,6-tribromophenol. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 407–414, 1998     

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.