scholarly journals Exploration of Ruthenium (III) Chloride catalysis on oxidative conversion of aryloximes to arylaldehydes with bromamine-B: A kinetic and mechanistic approach

2021 ◽  
Vol 23 (05) ◽  
pp. 240-261
Author(s):  
Manjunatha A S ◽  
◽  
Anu Sukhdev ◽  
Putta Swamy ◽  
Shashi Dhara T S ◽  
...  
Keyword(s):  
Fractional Order ◽  
Reaction Times ◽  
Activation Parameters ◽  
Oxidation Products ◽  
Isokinetic Temperature ◽  
Experimental Conditions ◽  
Mechanistic Approach ◽  
Different Temperatures ◽  
Plausible Mechanism ◽  
Catalyzed Reactions

Conversion of aryloximes to corresponding arylaldehydes is an important oxidative transformation in synthetic chemistry. In the course of this research, optimum conditions for the facile oxidation of benzaldehyde oxime and p-substituted benzaldehyde oximes viz., p-hydroxybenzaldehyde oxime, p-methoxy benzaldehyde oxime, p-bromobenzaldehyde oxime and p-nitrobenzaldehyde oxime (aryloximes) with bromamine–B (BAB) catalyzed by ruthenium (III) chloride (RuCl3) in perchloric acid (HClO4) medium have been kinetically investigated at 303 K. All the five aryloximes follow identical kinetics with a first-order dependence of rate on [BAB]o, fractional-order each on [aryloximes]o and [RuCl3], and an inverse fractional-order on [H+]. Activation parameters have been evaluated. Oxidation products were characterized by spectral analysis. Under the identical set of experimental conditions, the kinetics of catalyzed reactions has been compared with uncatalyzed reactions and found that the catalyzed reactions are 4–6 folds faster. Isokinetic temperature is found to be 338 K. The catalytic constants (Kc) have been calculated at different temperatures and the values of activation parameters with respect to the catalyst have been evaluated. Spectroscopic evidence for the formation of 1:1 complex between BAB and RuCl3 has been obtained. The observed results have been explained by a plausible mechanism and the related rate law has been deduced. The present method offers many advantages including high conversion, short reaction times and the involvement of non-toxic reagents.

scholarly journals Oxidation of some catecholamines by sodium N-chloro-p-toluenesulfonamide in acid medium: A kinetic and mechanistic approach

2005 ◽  
Vol 3 (2) ◽  
pp. 326-346 ◽  
Author(s):  
◽  
R. Jagadeesh ◽  
Nirmala Vaz
Keyword(s):  
Fractional Order ◽  
Reaction Rate ◽  
Oxidation Products ◽  
Solvent Isotope Effect ◽  
Experimental Conditions ◽  
Isokinetic Relationship ◽  
Mechanistic Approach ◽  
Chloramine T ◽  
Solvent Isotope ◽  
Kinetics Of

AbstractThe kinetics of the oxidation of five catecholamines viz., dopamine (A), L-dopa (B), methyldopa (C), epinephrine (D) and norepinephrine (E) by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in presence of HClO4 was studied at 30±0.1 °C. The five reactions followed identical kinetics with a first-order dependence on [CAT]o, fractional-order in [substrate]o, and inverse fractional-order in [H+]. Under comparable experimental conditions, the rate of oxidation of catecholamines increases in the order D>E>A>B>C. The variation of ionic strength of the medium and the addition of p-toluenesulfonamide or halide ions had no significant effect on the reaction rate. The rate increased with decreasing dielectric constant of the medium. The solvent isotope effect was studied using D2O. A Michaelis-Menten type mechanism has been suggested to explain the results. Equilibrium and decomposition constants for CAT-catecholamine complexes have been evaluated. CH3C6H4SO2NHCl of the oxidant has been postulated as the reactive oxidizing species and oxidation products were identified. An isokinetic relationship is observed with β=361 K, indicating that enthalpy factors control the reaction rate. The mechanism proposed and the derived rate law are consistent with the observed kinetics.

scholarly journals Oxidation of Tetracaine Hydrochloride by Chloramine-B in Acid Medium: Kinetic Modeling

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Jayachamarajapura Pranesh Shubha ◽  
Puttaswamy
Keyword(s):  
Dielectric Constant ◽  
Free Acid ◽  
Activation Parameters ◽  
Local Anaesthetics ◽  
Oxidation Products ◽  
Rate Variation ◽  
First Order ◽  
Order Dependence ◽  
Different Temperatures ◽  
Plausible Mechanism

Tetracaine hydrochloride (TCH) is one of the potent local anaesthetics. A kinetic study of oxidation of tetracaine hydrochloride by sodium N-chlorobenzenesulfonamide (chloramine-B or CAB) has been carried in HClO4 medium at 303 K. The rate shows first-order dependence on [CAB]o, shows fractional–order dependence on [substrate]o, and is self-governing on acid concentration. Decrease of dielectric constant of the medium, by adding methanol, increased the rate. Variation of ionic strength and addition of benzenesulfonamide or NaCl have no significant effect on the rate. The reaction was studied at different temperatures and the activation parameters have been evaluated. The stoichiometry of the reaction was found to be 1 : 5 and the oxidation products were identified by spectral analysis. The conjugate free acid C6H5SO2NHCl of CAB is postulated as the reactive oxidizing species. The observed results have been explained by plausible mechanism and the related rate law has been deduced.

scholarly journals Mechanistic aspects of oxidation on L-tyrosine by diperiodatocuprate(III) complex in alkali media: a kinetic model

2009 ◽  
Vol 7 (4) ◽  
pp. 929-937 ◽  
Author(s):  
Nagaraj Shetti ◽  
Rajesh Hegde ◽  
Sharanappa. Nandibewoor
Keyword(s):  
Alkaline Medium ◽  
Activation Parameters ◽  
Spectral Studies ◽  
Slow Step ◽  
Isokinetic Temperature ◽  
Thermodynamic Quantities ◽  
Radical Intermediate ◽  
Different Temperatures ◽  
Reactive Oxidant ◽  
Reaction Constants

AbstractOxidation of an amino acid, L-tyrosine (L-Tyr) by diperiodatocuprate(III) (DPC) in alkaline medium at a constant ionic strength of 0.1 mol dm−3 was studied spectrophotometrically at different temperatures (288.1–313.1 K). The reaction between DPC and L-Tyr in alkaline medium exhibits 1:4 stoichiometry (L-Tyr:DPC). Intervention of free radicals was observed in the reaction. Based on the observed orders and experimental evidence, a mechanism involving monoperiodatocuprate(III) (MPC) as the reactive oxidant species has been proposed. A suitable mechanism is proposed through the formation of a complex and free radical intermediate. The products were identified by spot test and characterized by spectral studies. The reaction constants involved in the different steps of the mechanism were calculated. The activation parameters with respect to slow step of the mechanism were computed and are discussed. The thermodynamic quantities were determined for different equilibrium steps. Isokinetic temperature was also calculated and found to be 252.3 K.

Temperature, Dynamics, and Enzyme-Catalyzed Reaction Rates

2020 ◽  
Vol 49 (1) ◽  
pp. 163-180 ◽  
Author(s):  
Vickery L. Arcus ◽  
Adrian J. Mulholland
Keyword(s):  
Molecular Mechanisms ◽  
Activation Parameters ◽  
Reaction Rates ◽  
Rate Theory ◽  
Different Temperatures ◽  
State Ensemble ◽  
Catalyzed Reactions ◽  
Enzyme Catalyzed Reactions ◽  
Transition State Ensemble ◽  
Rate Limiting

We review the adaptations of enzyme activity to different temperatures. Psychrophilic (cold-adapted) enzymes show significantly different activation parameters (lower activation enthalpies and entropies) from their mesophilic counterparts. Furthermore, there is increasing evidence that the temperature dependence of many enzyme-catalyzed reactions is more complex than is widely believed. Many enzymes show curvature in plots of activity versus temperature that is not accounted for by denaturation or unfolding. This is explained by macromolecular rate theory: A negative activation heat capacity for the rate-limiting chemical step leads directly to predictions of temperature optima; both entropy and enthalpy are temperature dependent. Fluctuations in the transition state ensemble are reduced compared to the ground state. We show how investigations combining experiment with molecular simulation are revealing fundamental details of enzyme thermoadaptation that are relevant for understanding aspects of enzyme evolution. Simulations can calculate relevant thermodynamic properties (such as activation enthalpies, entropies, and heat capacities) and reveal the molecular mechanisms underlying experimentally observed behavior.

Kinetics and Mechanism of Oxidation of Coumarin and Substituted Coumarins by Chloramine-b in Hydrochloric Acid Medium

2008 ◽  
Vol 33 (4) ◽  
pp. 313-330 ◽  
Author(s):  
J.P. Shubha ◽  
Puttaswamy
Keyword(s):  
Reaction Rate ◽  
Activation Parameters ◽  
Hydroxycinnamic Acids ◽  
Oxidation Products ◽  
Experimental Conditions ◽  
Isokinetic Relationship ◽  
Order Dependence ◽  
Rate Determining Step ◽  
Solvent Isotope ◽  
Substituted Coumarins

The kinetics of oxidation of coumarin (see Equation (1)) and four substituted coumarins, viz. 7-methoxycoumarin, 7-ethoxycoumarin, 7-hydroxycoumarin and 7-nitrocoumarin, to the corresponding o-hydroxycinnamic acids by chloramine-B (CAB) have been studied at 298 K. Under comparable experimental conditions, the reaction rate shows a first-order dependence each upon [CAB]o and [coumarin]o, and individually less than unit order dependence on [H+] and [Cl-]. Addition of benzenesulfonamide retards the reaction rate and the dielectric effect is positive. Variation of ionic strength of the medium does not influence the rate but the rate increases with increase in dielectric constant of the medium. The solvent isotope effect was studied using D2O. The reaction was studied at different temperatures and activation parameters have been evaluated. The stoichiometry of the reaction was found to be 1:1 and the oxidation products of coumarins were identified as their corresponding o-hydroxycinnamic acids. The rate of oxidation of coumarins increases in the order: 7-hydroxycoumarin > 7-ethoxycoumarin > 7-methoxycoumarin > coumarin > 7-nitrocoumarin. The rates satisfactorily correlate with the Hammett γ relationship and the reaction constant ρ is -0.04, which signifies that electron-donating groups enhance the rate and the electron-withdrawing group retards the rate. An isokinetic relationship was observed with β = 348 K, which showed the reaction to be enthalpy controlled. A mechanism consistent with the experimental results is proposed in which the rate-determining step is the formation of an intermediate complex between the substrate and molecular chlorine. The related rate law has been deduced and the decomposition constants were evaluated.

scholarly journals Kinetics and Mechanism of Micellar Catalyzed Oxidation of Dextrose by N-Bromosuccinimide in H2SO4 Medium

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Minu Singh
Keyword(s):  
Fractional Order ◽  
Activation Parameters ◽  
Kinetic Studies ◽  
Kinetics And Mechanism ◽  
Stoichiometric Ratio ◽  
Product Analysis ◽  
Experimental Conditions ◽  
First Order ◽  
Order Dependence ◽  
Wide Range

Kinetics and mechanism of micellar catalyzed N-bromosuccinimide oxidation of dextrose in H2SO4 medium was investigated under pseudo-first-order condition temperature of 40°C. The results of the reactions studied over a wide range of experimental conditions show that NBS shows a first order dependence, fractional order, on dextrose and negative fractional order dependence on sulfuric acid. The determined stoichiometric ratio was 1 : 1 (dextrose : N-bromosuccinimide). The variation of Hg(OAC)2 and succinimide (reaction product) has insignificant effect on reaction rate. Effects of surfactants, added acrylonitrile, added salts, and solvent composition variation have been studied. The Arrhenius activation energy and other thermodynamic activation parameters are evaluated. The rate law has been derived on the basis of obtained data. A plausible mechanism has been proposed from the results of kinetic studies, reaction stoichiometry, and product analysis. The role of anionic and nonionic micelle was best explained by the Berezin’s model.

Kinetic and Mechanistic Aspects of Osmium(VIII) Catalyzed Oxidation of DL-ornithine by Copper(III) Periodate Complex in Aqueous Alkaline Medium

2010 ◽  
Vol 224 (06) ◽  
pp. 865-882 ◽  
Author(s):  
Jyothi C. Abbar ◽  
Shweta J. Malode ◽  
Sharanappa T. Nandibewoor
Keyword(s):  
Alkaline Medium ◽  
Activation Parameters ◽  
Reaction Rates ◽  
Oxidation Products ◽  
Slow Step ◽  
Thermodynamic Quantities ◽  
Aqueous Alkaline Medium ◽  
Uncatalyzed Reaction ◽  
Different Temperatures ◽  
Reaction Constants

AbstractThe oxidation of DL-ornithine monohydrochloride (OMH) by diperiodatocuprate(III) (DPC) has been investigated in the presence of osmium(VIII) catalyst in aqueous alkaline medium at a constant ionic strength of 0.20 mol dm−3 spectrophotometrically. The reaction exhibits 1:4 stoichiometry i.e., [OMH]: [DPC]. The order of the reaction with respect to [DPC] was unity while the order with respect to [OMH] was less than unity over the concentration range studied. The rate increased with an increase in [OH –] and decreased with an increase in [IO4−]. The order with respect to [Os(VIII)] was unity. The reaction rates revealed that Os(VIII) catalyzed reaction was about nine-fold faster than the uncatalyzed reaction. The oxidation products were identified by spectral analysis. Suitable mechanism has been proposed. The reaction constants involved in the different steps of the reaction mechanism were calculated. The catalytic constant (KC) was also calculated 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 [OsO4(OH)2]2− is the reactive Os(VIII) species and [Cu(H2IO6)(H2O)2] is the reactive copper(III) species.

scholarly journals Kinetics of Oxidation of Metochlopramide withChloramine-T in HClO4 Medium

2009 ◽  
Vol 6 (2) ◽  
pp. 545-552 ◽  
Author(s):  
K. M. Meenakshi ◽  
K. Vasant Kumar Pai
Keyword(s):  
Thermodynamic Parameters ◽  
Fractional Order ◽  
Reaction Rate ◽  
Oxidation Products ◽  
Perchloric Acid Solution ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Different Temperatures ◽  
Negative Effect ◽  
Kinetics Of

The kinetics of oxidation of metochlopramide hydrochloride (MCP) with sodiumN-chlorop-toluenesulfonamide (CAT) in perchloric acid solution has been studied at 313K. The reaction rate shows a first order dependence on [CAT], fractional order on [MCP] and inverse fractional order on [H+]. There is a negative effect of dielectric constant of the solvent. The addition of the reduction product of CAT has no significant effect on the rate. The rate remained unchanged with the variation in the ionic strength of the medium. The reaction fails to induce the polymerization of acrylonitrile. Thermodynamic parameters have been computed by Arrhenius plot. The stoichiometry of the reaction was found to be 1:2 and oxidation products were identified. The Michaelis-Menten type of kinetics has been proposed. CH3C6H4SO2NHCl have been assumed to be the reactive oxidizing species. Thermodynamic parameters were computed by studying reactions at different temperatures. A mechanism consistent with observed kinetics is proposed.

scholarly journals Mechanistic investigations of oxidation of isatins by sodium N-chlorobenzenesulfonamide in alkaline medium: A kinetic study

2005 ◽  
Vol 3 (3) ◽  
pp. 482-501 ◽  
Author(s):  
◽  
R. Jagadeesh
Keyword(s):  
Alkaline Medium ◽  
Reaction Times ◽  
Activation Parameters ◽  
Cost Effective ◽  
Oxidation Products ◽  
High Yield ◽  
Rate Variation ◽  
Isokinetic Relationship ◽  
Anthranilic Acids ◽  
Solvent Isotope

AbstractOxidation of isatins (isatin, 5-methylisatin, 5-bromoisatin and 5-nitroisatin) to their anthranilic acids was performed efficiently with sodium N-chlorobenzenesulfonamide or chloramine-B (CAB) in alkaline medium at 35±0.1°C. The reactions follow identical kinetics for all the isatins, being first-order dependence each in [CAB]o and [Isatin]o and inverse fractional-order on [NaOH]. Addition of halide ions and benzenesulfonamide, reduction product of CAB, do not significantly affect the rate. Variation of ionic strength of the medium had no effect on the rate, while the dielectric effect is negative. The solvent isotope effect was studied using D2O. Activation parameters for the overall reaction have been computed. The rates satisfactorily correlate with the Hammett σ relationship and the reaction constant ρ is −0.31 signifies that electron releasing groups accelerate the reaction while the electron withdrawing groups retard the rate. Values of ΔH≠ and ΔS≠ are linearly related and an isokinetic relationship is observed with β=376 K, indicating the reaction is controlled by enthalpy. The stoichiometry of the title reaction is found to be 1∶1. Oxidation products of isatins were identified as their corresponding anthranilic acids and the yields were found to be around 90 %. The observed results have been explained by a plausible mechanism and the related rate law deduced. This method offers several advantages including high yield of the products, short reaction times, easier isolation of products, and stable, cost effective and relatively non-toxic reagents, which make the reaction process simple and smooth.

scholarly journals Kinetics and Mechanism of Oxidation of Tartaric Acid by N-Chloronicotinamide (NCN)

2015 ◽  
Vol 52 ◽  
pp. 120-125 ◽  
Author(s):  
L. Pushpalatha
Keyword(s):  
Acetic Acid ◽  
Tartaric Acid ◽  
Fractional Order ◽  
Rate Constants ◽  
Activation Parameters ◽  
First Order ◽  
First Order Kinetics ◽  
Different Temperatures ◽  
Mechanism Of Oxidation ◽  
Experimental Findings

The oxidation of tartaric acid by N-chloronicotinamide in the presence of HClO4 is studied. First order kinetics with respect to NCN is observed. The kinetics results indicate fractional order dependence about [tartaric acid]. Inverse first order in [nicotinamide] and inverse fractional order about [H+] are noted. Rate of the reaction increases with a decrease in the percentage of acetic acid. The values of rate constants observed at four different temperatures were utilized to calculate the activation parameters. A suitable mechanism consistent with the experimental findings has been proposed.

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