Mechanism of bromination of a quaternary pyrimidinium cation. Change of rate determining step with acidity

The kinetics of bromination of the 1,2-dihydro-1,3-dimethyl-2-oxopyrimidinium cation (Q+) in aqueous media (pH 0–5) have been studied using the stopped-flow method. At the higher acidities (pH < 2) the results are consistent with rate determining attack by bromine upon the pseudobase (QOH), whereas at low acidities (pH > 4) it appears that pseudobase formation is rate determining. The change occurs because at high acidity the reversal of the pseudobase QOH to the cation is fast relative to bromine attack, whereas at low acidity the converse is true. Results obtained at intermediate acidities (pH 2–4) are consistent with this interpretation.A separate kinetic study of pseudobase formation (and decomposition) yielded rate constants in good agreement with those derived from the bromination study.

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Kinetics of the Reversible Transformation of 2,3-Dioxogulonic Acid into its Enol as a Function of the pH of the Medium

Zeitschrift für Naturforschung A ◽

10.1515/zna-1978-1011 ◽

1978 ◽

Vol 33 (10) ◽

pp. 1184-1189

Author(s):

J. Zuluaga ◽

P. Martínez

Keyword(s):

Kinetic Study ◽

Equilibrium Constant ◽

Rate Constants ◽

Disodium Salt ◽

Stopped Flow ◽

Free Energies ◽

Reversible Transformation ◽

Flow Method ◽

Kinetic Coefficients ◽

Kinetics Of

Abstract 2,3-dioxogulonic acid and the disodium salt of its enol were synthesised, isolated and identified both chemically and spectroscopically. A kinetic study was carried out on its equilibrium by means of the “stopped flow” method for rapid processes, and the rate constants for the forward and backward reaction were determined as a function of the pH of the medium. The kinetic coefficients involved, equilibrium constant and Gibbs free energies were also determined.

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Reaction Kinetics of Carbon Dioxide in Aqueous Diethanolamine Solutions Using the Stopped-Flow Technique

Ecological Chemistry and Engineering S ◽

10.2478/v10216-011-0006-y ◽

2012 ◽

Vol 19 (1) ◽

pp. 55-66 ◽

Cited By ~ 5

Author(s):

Marta Siemieniec ◽

Hanna Kierzkowska-Pawlak ◽

Andrzej Chacuk

Keyword(s):

Carbon Dioxide ◽

Reaction Kinetics ◽

Rate Constants ◽

Reaction Rate ◽

Reaction Rate Constant ◽

Stopped Flow ◽

First Order ◽

Pseudo First Order ◽

Kinetics Of ◽

Good Agreement

Reaction Kinetics of Carbon Dioxide in Aqueous Diethanolamine Solutions Using the Stopped-Flow Technique The pseudo-first-order rate constants (kOV) for the reactions between CO2 and diethanolamine have been studied using the stopped-flow technique in an aqueous solution at 293, 298, 303 and 313 K. The amine concentrations ranged from 167 to 500 mol·m-3. The overall reaction rate constant was found to increase with amine concentration and temperature. Both the zwitterion and termolecular mechanisms were applied to correlate the experimentally obtained rate constants. The values of SSE quality index showed a good agreement between the experimental data and the corresponding fit by the use of both mechanisms.

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The kinetics of partial processes in the oxidation of ascorbic acid catalyzed by vanadyl tetrasulphophthalocyanine

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19820744 ◽

1982 ◽

Vol 47 (3) ◽

pp. 744-754 ◽

Cited By ~ 5

Author(s):

Dana M. Wagnerová ◽

Jaroslav Votruba ◽

Jürgen Blanck ◽

Josef Vepřek-Šiška

Keyword(s):

Experimental Data ◽

Ascorbic Acid ◽

Reaction Mechanism ◽

Rate Constants ◽

Stopped Flow ◽

Adaptive Identification ◽

Flow Method ◽

Acid Catalyzed ◽

Kinetics Of

The rapid partial reactions of the oxidation of ascorbic acid by dioxygen with vanadyl tetrasulphophthalocyanine as a catalyst were studied by the stopped-flow method. The experimental data were treated on a computer and compared with the kinetic implications resulting from the proposed mechanism. Application of the adaptive identification method led to quantitative solution of the mechanism, i.e. determination of the values of all the isolated rate constants of the reaction mechanism.

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Metal Enolates – Enamines – Enol Ethers: How Do Enolate Equivalents Differ in Nucleophilic Reactivity?

Synthesis ◽

10.1055/s-0037-1611634 ◽

2019 ◽

Vol 51 (05) ◽

pp. 1157-1170 ◽

Cited By ~ 4

Author(s):

Artem Leonov ◽

Daria Timofeeva ◽

Armin Ofial ◽

Herbert Mayr

Keyword(s):

Rate Constants ◽

Correlation Equation ◽

Stopped Flow ◽

Quinone Methides ◽

Enol Ethers ◽

Reactivity Descriptors ◽

Silyl Enol Ethers ◽

Nucleophilic Reactivity ◽

Kinetics Of ◽

Least Squares Minimization

The kinetics of the reactions of trimethylsilyl enol ethers and enamines (derived from deoxybenzoin, indane-1-one, and α-tetralone) with reference electrophiles (p-quinone methides, benzhydrylium and indolylbenzylium ions) were measured by conventional and stopped-flow photometry in acetonitrile at 20 °C. The resulting second-order rate constants were subjected to a least-squares minimization based on the correlation equation lg k = s N(N + E) for determining the reactivity descriptors N and s N of the silyl enol ethers and enamines. The relative reactivities of structurally analogous silyl enol ethers, enamines, and enolate anions towards carbon-centered electrophiles are determined as 1, 107, and 1014, respectively. A survey of synthetic applications of enolate ions and their synthetic equivalents shows that their behavior can be properly described by their nucleophilicity parameters, which therefore can be used for designing novel synthetic transformations.

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The Kinetics of Peroxynitrite on Insulin Nitration Damage

10.21203/rs.3.rs-61724/v1 ◽

2020 ◽

Author(s):

Congxiao Zhang ◽

Fusheng Sun ◽

Congjiang Zhang ◽

Yunjing Luo

Keyword(s):

Activation Energy ◽

Biological Activity ◽

Glucose Metabolism ◽

Rate Constants ◽

The Body ◽

Stopped Flow ◽

Tyrosine Nitration ◽

Protein Nitration ◽

Physiological Conditions ◽

Kinetics Of

Abstract Background: Insulin is one of the most important versatile hormones that is central to regulating the energy and glucose metabolism in the body. There has been accumulating evidence supporting that diabetes was associated with peroxynitrite and protein nitration, and insulin nitration induced by peroxynitrite affected its biological activity. Methods: In this paper, the kinetics of insulin nitration by peroxynitrite in physiological conditions was studied by the stopped flow technique. Results: We determined the values of the reactive rate constants of peroxynitrite decomposition and peroxynitrite-induced tyrosine nitration in the presence of insulin. The activation energy of peroxynitrite decomposition and 3-nitrotyrosine yield in the presence of insulin is 48.8 kJ·mol−1 and 42.7 kJ·mol−1 respectively. Conclusions: It is inferred that the glutamate residue of insulin accelerated peroxynitrite decomposition and tyrosine nitration by reducing the activation energy of reactions. The results could be beneficial for exploring the molecular mechanism of diabetes and offering a new target for diabetes therapies.

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Electrode kinetics of Eu3+/Eu2+ reaction by cyclic voltammetry

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19821773 ◽

1982 ◽

Vol 47 (7) ◽

pp. 1773-1779 ◽

Cited By ~ 1

Author(s):

T. P. Radhakrishnan ◽

A. K. Sundaram

Keyword(s):

Electron Transfer ◽

Rate Constants ◽

Outer Sphere ◽

Electrode Reaction ◽

Transfer Reactions ◽

Cyclic Voltammetric ◽

Edta Solution ◽

Kinetics Of ◽

Activated Complex ◽

Good Agreement

The paper is a detailed study of the cyclic voltammetric behaviour of Eu3+ at HMDE in molar solutions of KCl, KBr, KI, KSCN and in 0.1M-EDTA solution with an indigenously built equipment. The computed values of the rate constants at various scan rates show good agreement with those reported by other electrochemical methods. In addition, the results indicate participation of a bridged activated complex in the electron-transfer step, the rate constants showing the trend SCN- > I- > Br- > Cl- usually observed for bridging order of these anions in homogeneous electron-transfer reactions. The results for Eu-EDTA system, however, indicate involvement of an outer sphere activated complex in the electrode reaction.

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Double mixing stopped-flow method for the study of equilibria and kinetics of dimer-tetramer association of hemoglobins: Studies on Hb Carp, Hb A, and Hb Rothschild

Analytical Biochemistry ◽

10.1016/0003-2697(91)90457-5 ◽

1991 ◽

Vol 196 (2) ◽

pp. 223-228 ◽

Cited By ~ 7

Author(s):

Marjaneh Berjis ◽

Vijay S. Sharma

Keyword(s):

Stopped Flow ◽

Flow Method ◽

Kinetics Of

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Kinetic Study of the Oxidation of Alcohols with Quaternary Ammonium Permanganates

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19931777 ◽

1993 ◽

Vol 58 (8) ◽

pp. 1777-1781 ◽

Cited By ~ 3

Author(s):

Robert Šumichrast ◽

Vladislav Holba

Keyword(s):

Kinetic Study ◽

Catalytic Reaction ◽

Rate Constants ◽

Quaternary Ammonium ◽

Iterative Procedure ◽

Activation Parameters ◽

Reaction Products ◽

Thermodynamic Activation Parameters ◽

Oxidation Of Alcohols ◽

Kinetics Of

Kinetics of the oxidation of 2-propanol, 1-butanol, and 1-pentanol with tetraalkylammonium permanganates have been investigated as function of temperature. The studied reactions are partly autocatalytic, colloidal manganese dioxide as one of the reaction products has been identified as the autocatalyst.A computerized iterative procedure has been used in order to obtained the rate constants of both non-catalytic and catalytic reaction steps together with the thermodynamic activation parameters.

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