Kinetics of Formation of Ca2+Complexes of Acyclic and Macrocyclic Poly(amino carboxylate) Ligands:  Bimolecular Rate Constants for the Fully-Deprotonated Ligands Reveal the Effect of Macrocyclic Ligand Constraints on the Rate-Determining Conversions of Rapidly-Formed Intermediates to the Final Complexes

1997 ◽  
Vol 36 (9) ◽  
pp. 1884-1889 ◽  
Author(s):  
Shu Ling Wu ◽  
Kenneth A. Johnson ◽  
William DeW. Horrocks
Keyword(s):  
Rate Constants ◽  
Macrocyclic Ligand ◽  
Carboxylate Ligands ◽  
Kinetics Of Formation ◽  
Kinetics Of

The time-resolved fluorescence study of kinetics and thermodynamics of Eu(iii) and Tb(iii) complexes with the DO2A macrocyclic ligand

2018 ◽  
Vol 42 (10) ◽  
pp. 7993-8000
Author(s):  
Filip Smrčka ◽  
Přemysl Lubal
Keyword(s):  
Fluorescence Spectroscopy ◽  
Macrocyclic Ligand ◽  
Time Resolved Fluorescence ◽  
Fluorescence Study ◽  
Time Resolved ◽  
Kinetics And Thermodynamics ◽  
Thermodynamics And Kinetics ◽  
Kinetics Of Formation ◽  
Kinetics Of

The thermodynamics and kinetics of formation/dissociation of Eu(iii) and Tb(iii) with the H2DO2A macrocyclic ligand were studied by time-resolved fluorescence spectroscopy.

scholarly journals The kinetics of formation of horseradish peroxidase compound I by reaction with peroxobenzoic acids. pH and peroxo acid substituent effects

1976 ◽  
Vol 157 (1) ◽  
pp. 247-253 ◽  
Author(s):  
D M Davies ◽  
P Jones ◽  
D Mantle
Keyword(s):  
Horseradish Peroxidase ◽  
Active Site ◽  
Rate Constants ◽  
Ph Effect ◽  
Substituent Effects ◽  
Nucleophilic Attack ◽  
Compound I ◽  
Active Intermediate ◽  
Kinetics Of Formation ◽  
Kinetics Of

1. The kinetics of formation of horseradish peroxidase Compound I were studied by using peroxobenzoic acid and ten substituted peroxobenzoic acids as substrates. Kinetic data for the formation of Compound I with H2O2 and for the reaction of deuteroferrihaem with H2O2 and peroxobenzoic acids, to form a peroxidatically active intermediate, are included for comparison. 2. The observed second-order rate constants for the formation of Compound I with peroxobenzoic acids decrease with increasing pH, in the range pH 5-10, in contrast with pH-independence of the reaction with H2O2. The results imply that the formation of Compound I involves a reaction between the enzyme and un-ionized hydroperoxide molecules. 3. The maximal rate constants for Compound I formation with unhindered peroxobenzoic acids exceed that for H2O2. Peroxobenzoic acids with bulky ortho substituents show marked adverse steric effects. The pattern of substituent effects does not agree with expectations for an electrophilic oxidation of the enzyme by peroxoacid molecules in aqueous solution, but is in agreement with that expected for a reaction involving nucleophilic attack by peroxo anions. 4. Possible reaction mechanisms are considered by which the apparent conflict between the pH-effect and substituent-effect data may be resolved. A model in which it is postulated that a negatively charged ‘electrostatic gate’ controls access of substrate to the active site and may also activate substrate within the active site, provides the most satisfactory explanation for both the present results and data from the literature.

Kinetics of the anation reaction of nickel(II) and 1,10-phenanthroline in methanol–water mixtures

1969 ◽  
Vol 47 (20) ◽  
pp. 3773-3778 ◽  
Author(s):  
M. L. Sanduja ◽  
W. MacF. Smith
Keyword(s):  
Ionic Strength ◽  
Rate Constant ◽  
Rate Constants ◽  
Solvent Composition ◽  
Solvent Mixtures ◽  
Methanol Content ◽  
Dependent Rate ◽  
Kinetics Of Formation ◽  
Kinetics Of ◽  
Anation Reaction

The kinetics of formation of the monophenanthroline complex of nickel(II) has been studied spectrophotometrically in water–methanol mixtures of 0 to 97 weight % of methanol, at ionic strength 0.050, at varying acidities at 25 °C. Values for the rate constants for the acid independent and acid dependent reactions together with values for the equilibrium acid ionization quotient of phenanthrolium ion over the range of solvent mixtures have been determined. The values of the acid independent rate constant show little dependence on solvent compositions up to 76% methanol, then decrease and show no correlation with trends in the ionization quotient of phenanthrolium ion. The acid dependent rate constant shows only a modest dependence on solvent composition over most of the range of solvent compositions except in the range of highest methanol content where it is not significantly different from zero.

A chemiluminescence study of the kinetics of reactions of Cr(III) with carboxylate ligands: oxalate, salicylate, and humic acid

1990 ◽  
Vol 68 (6) ◽  
pp. 881-885 ◽  
Author(s):  
Douglas L. Huizenga ◽  
Howard H. Patterson
Keyword(s):  
Humic Acid ◽  
Reaction Kinetics ◽  
Rate Constants ◽  
Natural Waters ◽  
Ligand Concentration ◽  
Reaction Pathways ◽  
Carboxylate Ligands ◽  
Kinetics Of ◽  
Insight Into

The reaction of Cr(III) with chelate-forming carboxylate ligands can be monitored at the low ligand concentrations typical of natural waters by chemiluminescence analysis of unreacted Cr(III). This technique is utilized here for the measurement of Cr(III) reaction kinetics with oxalate, salicylate, and humic acid over a wider ligand concentration range than previously reported. Variation of the pH and ligand concentrations allowd the determination of rates of reaction by three pathways with different pH dependencies. The magnitude of rate constants of these pathways for Cr(III) with inorganic (Cl−, SCN−) and carboxylate ligands gives insight into the reaction pathways for the environmentally important ligand humic acid. Keywords: Cr(III), oxalate, salicylate, humic acid.

The kinetics of formation of electron donor–acceptor complexes. A temperature-jump study

1990 ◽  
Vol 68 (2) ◽  
pp. 278-281 ◽  
Author(s):  
M. A. Zon ◽  
H. Fernandez ◽  
L. Sereno ◽  
J. J. Silber
Keyword(s):  
Electron Donor ◽  
Rate Constants ◽  
Temperature Jump ◽  
Diffusion Control ◽  
Diffusion Controlled ◽  
Kinetics Of Formation ◽  
Donor Acceptor ◽  
Eda Complex ◽  
Kinetics Of

The kinetics of the Electron Donor–Acceptor (EDA) complex between N,N,N′,N′-tetramethyl-p-phenylenediamine and m-dinitrobenzene in acetonitrile has been studied by the temperature-jump technique. The magnitude of the rate constants of association and dissociation, although relatively large, is well below the diffusion control values. The calculated rates closely coincide with those obtained by chronoamperometry. An entropy control is suggested for this reaction. The results obtained in this work are useful to demonstrate that the concept about EDA complexes being formed by diffusion-controlled reactions should not be generalized. Keywords: electron donor–acceptor complexes, m-dinitrobenzene, N,N,N′,N′-tetramethyl-p-phenylenediamine, T-jump, kinetics.

Molecular complexes of iodine with cyclic polyethers in chloroform: Kinetics of formation

1983 ◽  
Vol 48 (4) ◽  
pp. 1158-1161 ◽  
Author(s):  
Jana Muchová ◽  
Vladislav Holba
Keyword(s):  
Temperature Dependence ◽  
Rate Constants ◽  
Molecular Complexes ◽  
Kinetics Of Formation ◽  
Cyclic Polyethers ◽  
Absorbance Changes ◽  
Kinetics Of

Absorbance changes of solutions of iodine and 15-crown-5, 18-crown-6 and dibenzo-18-crown-6 in chloroform were studied. Absorption maxima due to the triiodide anion were observed. The obtained rate constants and their temperature dependence indicate formation of molecular complexes (cyclic polyether...I2) and (cyclic polyether...I(+)) I(-).

Submerged upflow biotower operation and computer simulation

1994 ◽  
Vol 30 (11) ◽  
pp. 143-146
Author(s):  
Ronald D. Neufeld ◽  
Christopher A. Badali ◽  
Dennis Powers ◽  
Christopher Carson
Keyword(s):  
Computer Simulation ◽  
Benzoic Acid ◽  
Computer Model ◽  
Rate Constants ◽  
Batch Mode ◽  
Operational Conditions ◽  
First Order ◽  
Low Concentrations ◽  
Biological Transformation ◽  
Kinetics Of

A two step operation is proposed for the biodegradation of low concentrations (< 10 mg/L) of BETX substances in an up flow submerged biotower configuration. Step 1 involves growth of a lush biofilm using benzoic acid in a batch mode. Step 2 involves a longer term biological transformation of BETX. Kinetics of biotransformations are modeled using first order assumptions, with rate constants being a function of benzoic acid dosages used in Step 1. A calibrated computer model is developed and presented to predict the degree of transformation and biomass level throughout the tower under a variety of inlet and design operational conditions.

Kinetics of cyclization of S-ethoxycarbonylmethylisothiouronium chloride to 2-imino-4-thiazolidone

1979 ◽  
Vol 44 (3) ◽  
pp. 912-917 ◽  
Author(s):  
Vladimír Macháček ◽  
Said A. El-bahai ◽  
Vojeslav Štěrba
Keyword(s):  
Hydrochloric Acid ◽  
Dilute Hydrochloric Acid ◽  
Base Catalysis ◽  
General Base ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Rate Limiting ◽  
Kinetics Of

Kinetics of formation of 2-imino-4-thiazolidone from S-ethoxycarbonylmethylisothiouronium chloride has been studied in aqueous buffers and dilute hydrochloric acid. The reaction is subject to general base catalysis, the β value being 0.65. Its rate limiting step consists in acid-catalyzed splitting off of ethoxide ion from dipolar tetrahedral intermediate. At pH < 2 formation of this intermediate becomes rate-limiting; rate constant of its formation is 2 . 104 s-1.

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