Studies on Lactoperoxidase. VI. Kinetics of the Oxidation of p-Cresol by Compound II

1973 ◽  
Vol 51 (11) ◽  
pp. 1721-1723 ◽  
Author(s):  
R. James Maguire ◽  
H. Brian Dunford
Keyword(s):  
Dissociation Constants ◽  
Acid Dissociation ◽  
Stopped Flow ◽  
Acid Dissociation Constants ◽  
First Order ◽  
Diffusion Controlled ◽  
Ph Range ◽  
Rate Profile ◽  
Compound Ii ◽  
Kinetics Of

The kinetics of the oxidation of p-cresol by compound II of lactoperoxidase have been studied over the pH range 2.1–11.2 by the stopped-flow technique. The reaction is kinetically first-order with respect to p-cresol over the entire pH range. Use is made of the diffusion-controlled limit that can be placed on a bimolecular rate constant to show that p-cresol reacts in the unionized form. The complexity of the pH-rate profile is discussed in terms of acid dissociation constants of groups in the enzyme and the ionization of the substrate.

The comparative chemistry of ammine and methylamine complexes of rhodium(III) and cobalt(III)

1977 ◽  
Vol 55 (17) ◽  
pp. 3166-3171 ◽  
Author(s):  
Thomas Wilson Swaddle
Keyword(s):  
Ionic Strength ◽  
Spectral Data ◽  
Electron Donor ◽  
Dissociation Constants ◽  
Base Hydrolysis ◽  
Acid Dissociation ◽  
Rate Coefficients ◽  
Acid Dissociation Constants ◽  
First Order ◽  
Kinetics Of

For the aquation of (CH3NH2)5RhCl2+, the first order rate coefficients are represented by ΔHaq* = 101.9 kJ mol−1 and ΔSaq* = −50.2 JK−1 mol−1 in 0.1 M HClO4, while for base hydrolysis the rate is first order in [(CH3NH2)5RhCl2+] and [OH−] at ionic strength 0.10 M and the rate coefficients (in M−1 s−1) are represented by ΔHOH*> = 108.6 kJ mol−1 and ΔSOH* = 74.1 J K−1 mol−1. Acid dissociation constants are reported for (RNH2)5MOH23+ (R = H or CH3; M = Rh or Co), and these, combined with spectral data, show CH3NH2 to be a poorer electron donor than NH3 in complexes of this type, contrary to expectations. The comparative kinetics of reactions of (RNH2)5MCl2+ support the assignment of an Ia mechanism to aquation when M = Rh or Cr, Id to aquation when M = Co, and Dcb for base hydrolysis in all these cases.

Kinetics and mechanism of disproportionation and ferricyanide oxidation of the 10-methylacridinium cation in aqueous base

1984 ◽  
Vol 62 (4) ◽  
pp. 729-735 ◽  
Author(s):  
John W. Bunting ◽  
Glenn M. Kauffman
Keyword(s):  
Ionic Strength ◽  
Second Order ◽  
Kinetics And Mechanism ◽  
Oxidation Pathway ◽  
First Order ◽  
Aqueous Base ◽  
Ph Range ◽  
Rate Profile ◽  
Kinetics Of ◽  
Major Oxidation

The kinetics of disproportionation and ferricyanide ion oxidation of the 10-methylacridinium cation have been measured spectrophotometrically over the pH range 9–14 in.20% CH3CN – 80% H2O (v/v) and ionic strength 1.0 at 25 °C. Disproportionation is kinetically second-order in total acridine species. The pH–rate profile is consistent with the rate-determining reaction of one acridinium cation with the pseudobase alkoxide anion derived from a second acridinium cation. Ferricyanide ion oxidation is kinetically first-order in each of ferricyanide ion and total acridine species. The pH–rate profile requires three distinct pathways for the ferricyanide ion oxidation of the 10-methylacridinium cation. For pH < 9.7, rate-determining attack of ferricyanide ion on the neutral pseudobase predominates, while for pH > 12.8 the predominant oxidation pathway involves reaction of ferricyanide ion with the pseudobase alkoxide ion. Between pH 9.7 and 12.8, the major oxidation pathway involves initial disproportionation of the acridinium cation followed by ferricyanide ion oxidation of the 9,10-dihydro-10-methylacridine product. This latter route accounts for a maximum of 69% of the total ferricyanide ion oxidation at pH 11.1.

Studies of reagents for spectrophotometric measurement of ionic magnesium

1977 ◽  
Vol 55 (22) ◽  
pp. 3909-3914 ◽  
Author(s):  
Dennis G. McMinn ◽  
Byron Kratochvil
Keyword(s):  
Complex Formation ◽  
Dissociation Constants ◽  
Formation Constants ◽  
Acid Dissociation ◽  
Disulfonic Acid ◽  
Acid Dissociation Constants ◽  
Spectrophotometric Measurement ◽  
Ph Range ◽  
Metal Ligand ◽  
The Ideal

Four mono-azo aryl dyes having the o-carboxy-o′-hydroxy functionality were investigated as reagents for the measurement of ionic Mg2+ in solutions containing complexing ligands. 2-(2′-Carboxyl-1′-benzeneazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid came closest to the ideal of having absorbance unaffected by pH over the pH range of interest and of differentiating between Ca2+ and Mg2+ complex formation. Ligand acid dissociation constants and formation constants for the metal–ligand complexes were measured.

Studies on Horseradish Peroxidase. VII. A Kinetic Study of the Oxidation of Iodide by Horseradish Peroxidase Compound II

1971 ◽  
Vol 49 (18) ◽  
pp. 3059-3063 ◽  
Author(s):  
R. Roman ◽  
H. B. Dunford ◽  
M. Evett
Keyword(s):  
Ionic Strength ◽  
Horseradish Peroxidase ◽  
Kinetic Study ◽  
Rate Constant ◽  
Ph Dependence ◽  
Order Rate Constant ◽  
Acid Dissociation ◽  
Ph Range ◽  
Compound Ii ◽  
Kinetics Of

The kinetics of the oxidation of iodide ion by horseradish peroxidase compound II have been studied as a function of pH at 25° and ionic strength of 0.11. The logarithm of the second-order rate constant decreases linearly from 2.3 × 105 to 0.1 M−1 s−1 with increasing pH over the pH range 2.7 to 9.0. The pH dependence of the reaction is explained in terms of an acid dissociation outside the pH range of the study.

Kinetics of the Cu(II) – Nitrilotriacetic Acid Reaction

1974 ◽  
Vol 52 (24) ◽  
pp. 4106-4108 ◽  
Author(s):  
James Maguire
Keyword(s):  
Complex Formation ◽  
Nitrilotriacetic Acid ◽  
Stopped Flow ◽  
Kinetic Behavior ◽  
First Order ◽  
Acid Reaction ◽  
Decreasing Ph ◽  
Ph Range ◽  
Rate Limiting ◽  
Kinetics Of

The kinetics of the reaction between Cu(II) and nitrilotriacetic acid (NTA) to form the 1:1 complex have been studied by the stopped-flow technique over the pH range 2–6. The reaction is kinetically first order in both [Cu(II)] and [NTA]total; the rate constant has a minimum value of 1.1 × 105 l mol−1 s−1 in the pH range 3.5–5 and increases with either increasing or decreasing pH. An explanation for the observed kinetic behavior may be that in the case of the monoprotonated species HNTA2− there is a rate-limiting transfer of a proton from nitrogen before complex formation takes place, and that this transfer is facilitated with increasing acidity.

Kinetics of acid-catalysed hydrolysis of the α and β Carbonato(4,7-dimethyltriethylenetetramine) cobalt(III) ions

1974 ◽  
Vol 27 (2) ◽  
pp. 269 ◽  
Author(s):  
DJ Francis ◽  
GH Searle
Keyword(s):  
Acid Hydrolysis ◽  
Perchloric Acid ◽  
Rate Constants ◽  
Dissociation Constants ◽  
Bond Cleavage ◽  
Acid Dissociation ◽  
Acid Dissociation Constants ◽  
Rate Laws ◽  
Kinetics Of ◽  
Hydrolysis Of

The synthesis and separation of the complexes α-[Co(dmtr)CO3] ClO4 and β-[Co(dmtr)CO3] C1O4,H2O (dmtr = 4,7-dimethyltriethylenetetramine or N,N'-bis(2-aminoethyl)-N,N'-dimethylethane-1,2-diamine) are described. The kinetics of the acid hydrolysis of both complexes, studied in perchloric acid at 25�C and μ = 1.0M (LiC1O4), follow rate laws of form -d[complex]dt=(k0 + k1[H+I)[complex] The values of ko and k1 for the K-complex are 1.0 x 10-3 s-1 and 1.8 x 10-2 1. mol-1 s-1 respectively, while for the β-complex the corresponding values are 3.6 x 10-5 s-1 and 5.6 x 10-4 1. mol-1 s-1. Comparisons of these rate constants with the values for similar carbonato(tetramine)cobalt(111) complexes previously studied suggest that the ko path could involve O-C bond cleavage in the present dmtr complexes. The values of the acid dissociation constants of dmtr,4HCl, determined by potentiometric titration, are 1.61, 5.86, 8.18 and 9.95.

scholarly journals The Kinetics of Chitosan Degradation in Organic Acid Solutions

Marine Drugs ◽  
2021 ◽  
Vol 19 (5) ◽  
pp. 236
Author(s):  
Dominik Sikorski ◽  
Karolina Gzyra-Jagieła ◽  
Zbigniew Draczyński
Keyword(s):  
Organic Acid ◽  
Dissociation Constants ◽  
Degradation Process ◽  
Acid Dissociation ◽  
Acid Solutions ◽  
Spectroscopy Analysis ◽  
Acid Dissociation Constants ◽  
Spinning Process ◽  
Kinetics Of ◽  
Selection Of

This paper presents a comparative study on chitosan degradation in organic acid solutions according to their different dissociation characteristics. More precisely, the aim of the study was to determine the kinetics of the degradation process depending on the different acid dissociation constants (pKa values). The scientists involved in chitosan to date have focused mainly on acetic acid solutions. Solutions of lactic, acetic, malic, and formic acids in concentrations of 3% wt. were used in this research. The progress of degradation was determined based on the intrinsic viscosity measurement, GPC/SEC chromatographic analysis, and their correlation. Changes in the viscosity parameters were performed at a temperature of 20 °C ± 1 °C and a timeframe of up to 168 h (7 days). The chemical structure and DDA of the initial chitosan were analyzed using 1H-NMR spectroscopy analysis. The results of this study can be considered of high importance for the purpose of electrospinning, production of micro- and nano-capsules for drug delivery, and other types of processing. Understanding the influence of the dissociation constant of the solvent on the kinetics of chitosan degradation will allow the selection of an appropriate medium, ensuring an effective and stable spinning process, in which the occurrence of polymer degradation is unfavorable.

Kinetic of oxidation of methyl orange by vanadium(V) under conditions VO2+ and decavanadates coexist: Catalysis by Triton X-100 micellar medium

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Methyl Orange ◽  
Solution Ph ◽  
Vanadium Concentration ◽  
Limiting Behavior ◽  
First Order ◽  
First Order Kinetics ◽  
Ph Range ◽  
Kinetic Pattern ◽  
Triton X ◽  
Kinetics Of

The kinetics of oxidation of methyl orange by vanadium(V) {V(V)} has been investigated in the pH range 2.3-3.79. In this pH range V(V) exists both in the form of decavanadates and VO2+. The kinetic results are distinctly different from the results obtained for the same reaction in highly acidic solution (pH &lt; 1) where V(V) exists only in the form of VO2+. The reaction obeys first order kinetics with respect to methyl orange but the rate has very little dependence on total vanadium concentration. The reaction is accelerated by H+ ion but the dependence of rate on [H+] is less than that corresponding to first order dependence. The equilibrium between decavanadates and VO2+ explains the different kinetic pattern observed in this pH range. The reaction is markedly accelerated by Triton X-100 micelles. The rate-[surfactant] profile shows a limiting behavior indicative of a unimolecular pathway in the micellar pseudophase.

Analyses of the Acid Dissociation Constants of Multisubstituted Diarylamines Measured in Solvents and Micellar System

1994 ◽  
Vol 67 (3) ◽  
pp. 800-806 ◽  
Author(s):  
Ze-jian Guo ◽  
Hideto Miyoshi ◽  
Toshio Fujita
Keyword(s):  
Dissociation Constants ◽  
Acid Dissociation ◽  
Micellar System ◽  
Acid Dissociation Constants
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