16917-09-2Relevant academic research and scientific papers
Oxidation of ethanolamines by sodium N-bromobenzenesulfonamide in alkaline buffer medium: A kinetic and mechanistic study
Puttaswamy,Vaz, Nirmala,Made Gowda
, p. 480 - 490 (2001)
The kinetics of oxidation of ethanolamines, monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA), by sodium N-bromobenzenesulfonamide or bromamine-B (BAB) in alkaline buffer medium (pH 8.7-12.2) has been studied at 40°C. The three reactions follow identical kinetics with first-order in [oxidant] and fractional-order each in [substrate] and [OH-]. Under comparable experimental conditions, the rate of oxidation increases in the order: DEA > TEA > MEA. The added reaction product, benzenesulfonamide, retards the reaction rate. The addition of halide ions and the variation of ionic strength of the medium have no significant effect on the rate. The dielectric effect is negative. The solvent isotope effect k′(H2O)/k′(D2O) ≈ 0.92. Activation parameters for the composite reaction and for the rate-limiting step were computed from the Eyring plots, Michaelis-Menten type of kinetics is observed. The formation and decomposition constants of ethanolamine-BAB complexes are evaluated. An isokinetic relationship is observed with β = 430 K indicating that enthalpy factors control the rate. For each substrate, a mechanism consistent with the kinetic data has been proposed.
Palladium(II)-catalyzed oxidation of tranexamic acid by bromamine-B in alkaline medium and uncatalyzed reaction in acid medium: A study of kinetic and mechanistic chemistry
Puttaswamy,Sukhdev, Anu,Shubha
, p. 113 - 121 (2010)
Tranexamic acid (TA) possess antifibrinolytic properties and finds extensive applications in pharmaceuticals. Its oxidation-kinetic study is of much significance in understanding the mechanistic profile of TA in biological systems. In this context, a systematic kinetic study of palladium(II) (Pd(II)) catalyzed oxidation of TA by sodium N-bromobenzenesulfonamide or bromamine-B (BAB) in alkaline medium and uncatalyzed reaction in perchloric acid medium at 303 K was investigated. In acid medium, the reaction exhibits a first-order dependence of rate on [BAB]o and less than unity order dependence on [TA]o. The reaction rate shows inverse less than unity order dependence with respect to [H+]. In alkaline medium, the reaction shows first-order dependence on both [BAB]o and [Pd(II)] and zero-order with respect to [TA]o. The order with respect to [OH -] is less than unity. Activation parameters have been evaluated. The oxidation reactions are nearly 10-fold faster in acid medium in comparison with alkaline medium. In alkaline medium, the Pd(II) catalyzed reactions are about 6-fold faster than the uncatalyzed reaction. Further, the catalytic constant (KC) has been calculated at different temperatures and activation parameters with respect to Pd(II) catalyst have also been evaluated. The conjugate acid C6H5SO2NHBr and the anion C 6H5SO2N-Br of BAB have been postulated as the reactive oxidizing species in acid and alkaline media, respectively. The proposed mechanisms and derived rate laws are in agreement with the observed kinetics.
Catalysis and mechanistic studies of ruthenium and osmium on synthesis of anthranilic acids
Karthikeyan,Jagadeesh, Rajenahally V.,Sree Sandhya,Puttaswamy,Nithya,Kumar, S. Senthil,Bhagat
experimental part, p. 34 - 46 (2011/09/16)
Ruthenium, osmium and ruthenium + osmium catalyzed synthetic methodology was developed for the synthesis of anthranilic acids from indoles in good to excellent yields using bromamine-B in alkaline acetonitrile-water (1:1) at 313 K. Detailed catalysis studies of ruthenium, osmium and the mixture of both were carried out for the synthetic reactions. The positive synergistic catalytic activity of Ru(III) + Os(VIII) was observed to a large extent with the activity greater than the sum of their separate catalytic activities. Detailed kinetic and mechanistic investigations for each catalyzed reactions were carried out. The kinetic pattern and mechanistic picture of each catalyzed reaction were found to be different for each catalyst and to obey the underlying rate laws: rate = k[BAB]t[Indole][Ru(III)]x[OH-] y rate = k[BAB]t[Indole][Os(VIII)][OH-] y rate = k[BAB]t[Indole]o[Ru(III) + Os(VIII)][OH-]y where, x, y Os(VIII) > Ru(III). This trend may be attributed to the different d-electronic configuration of the catalysts. The proposed mechanisms and the rigorous kinetic models derived give results that fit well with the experimental data in each catalyzed reaction. Copyright
Bromamine-B/PdCl2 is an efficient system for the synthesis of anthranilic acids from indoles and indigos
Kumar, C. Vinod,Shivananda,Raju, C. Nagu,Jagadeesh
experimental part, p. 3480 - 3487 (2011/02/22)
A convenient method has been developed for the conversion of indoles and indigos into anthranilic acids in good to excellent yields using a bromamine-B/PdCl2 system. The general process utilizes our efficient method for the oxidation of indoles and indigos in alkaline (pH 12) acetonitrile/water (1:1) at 60°C. Copyright Taylor & Francis Group, LLC.
Oxidation of L-tyrosine by sodium N-bromobenzenesulfonamide in alkaline medium: A kinetic and mechanistic study
Puttaswamy,Vaz, Nirmala
, p. 479 - 483 (2007/10/03)
The kinetics of oxidation of L-tyrosine (Tyr) by sodium N-bromobenzenesulfonamide or bromamine-B (BAB) has been studied in NaOH medium at 283 K. The rates are first order in both [BAB]o and [Tyr] o and inverse fractional order in [OH-]. Ionic strength and halide ion variations or the presence of added reaction product, benzenesulfonamide, has no pronounced effect on the rate. The dielectric effect is positive. The reaction has been studied at different temperatures and activation parameters for the composite reaction are computed. Solvent isotope effect is also studied. The thermodynamic parameters for the equilibrium step and activation parameters for the rate determining step are evaluated. A plausible mechanism consistent with the observed kinetics is proposed.
Kinetic analysis of oxidation of dipeptides by sodium N-bromobenzenesulfonamide in acid medium: A mechanistic approach
Puttaswamy,Vaz, Nirmala
, p. 73 - 80 (2007/10/03)
The kinetics of the oxidation of five dipeptides (DPP) viz., glycylglycine (Gly-Gly), L-alanyl-L-alanine (Ala-Ala), L-valyl-L-valine (Val-Val), L-leucyl-L-leucine (Leu-Leu), and phenylglycyl-phenylglycine (Phg-Phg) by sodium N-bromobenzenesulfonamide or bromamine-B (BAB) in presence of HClO4 was studied at 40 °C. The five reactions followed identical kinetics with a first-order dependence on [BAB] and fractional order in [DPP]. At [H+] > 0.04 mol dm-3, the rate was inverse fractional in [H+], but zero order at lower [H+] (≤ 0.04 mol dm-3). A variation of the ionic strength or dielectric constant of the medium and the addition of halide ions and benzenesulfonamide had no effect on the rate of the reaction. Proton inventory studies were made in H2O-D2O mixtures for all five dipeptides. A Michaelis-Menten type mechanism has been suggested to explain the results. The decomposition and equilibrium constants were evaluated. The oxidation products were identified. The isokinetic temperature was 360 K, indicating the enthalpy to be a controlling factor. The rate of oxidation increased in the order Phg-Phg > Ala-Ala > Val-Val > Leu-Leu > Gly-Gly. The kinetics of oxidation of dipeptides was compared with those of their corresponding monomer amino acids, namely Phenylglycine, alanine, valine, leucine, and glycine. A general mechanism was proposed and the derived rate law are consistent with the observed kinetics.
