Kinetics and mechanism of the bromination of 4-pyridone and related derivatives in aqueous solution

1983 ◽  
Vol 61 (11) ◽  
pp. 2556-2562 ◽  
Author(s):  
Oswald S. Tee ◽  
Martino Paventi
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Point Of View ◽  
Kinetics And Mechanism ◽  
Ph Range ◽  
Kinetics Of

The kinetics of bromination of 4-pyridone and selected derivatives have been measured in aqueous solutions in the pH range 0–9, at 25 °C. The tautomeric system 4-pyridone [Formula: see text] 4-hydroxypyridine [Formula: see text] reaets with bromine via the predominant (pyridone) tautomer at pH < 6 and via the conjugate anion at pH > 6. 3-Bromo-4-pyridone behaves similarly. The kinetics also reveal that the facile dibromination of 4-pyridone occurs because at most pH's the monobromo derivative is actually more reactive towards bromine by virtue of its lower pKa values. From the point of view of reactivity the 4-pyridones and their anions behave as substituted phenoxide ions. 4-Methoxypyridine does not undergo bromination under comparable conditions, but rather forms a complex with bromine.

Kinetics and mechanism of the reaction of iron(III) with 6-methyl-2,4-heptanedione and 3,5-heptanedione

1990 ◽  
Vol 55 (8) ◽  
pp. 1984-1990 ◽  
Author(s):  
José M. Hernando ◽  
Olimpio Montero ◽  
Carlos Blanco
Keyword(s):  
Aqueous Solution ◽  
Metal Ion ◽  
Activation Parameters ◽  
Enol Form ◽  
Kinetics And Mechanism ◽  
Kinetic Constants ◽  
Steric Factors ◽  
Kinetics Of ◽  
Mechanism Of The Reaction

The kinetics of the reactions of iron(III) with 6-methyl-2,4-heptanedione and 3,5-heptanedione to form the corresponding monocomplexes have been studied spectrophotometrically in the range 5 °C to 16 °C at I 25 mol l-1 in aqueous solution. In the proposed mechanism for the two complexes, the enol form reacts with the metal ion by parallel acid-independent and inverse-acid paths. The kinetic constants for both pathways have been calculated at five temperatures. Activation parameters have also been calculated. The results are consistent with an associative activation for Fe(H2O)63+ and dissociative activation for Fe(H2O)5(OH)2+. The differences in the results for the complexes of heptanediones studied are interpreted in terms of steric factors.

scholarly journals Laboratory-scale photomineralisation of n-alkanes in aqueous solution, by photocatalytic membranes immobilising titanium dioxide

2005 ◽  
Vol 7 (2) ◽  
pp. 79-85 ◽  
Author(s):  
Ignazio Renato Bellobono ◽  
Franca Morazzoni ◽  
Riccardo Bianchi ◽  
Emilia Simona Mangone ◽  
Rodica Stanescu ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Photocatalytic Oxidation ◽  
Point Of View ◽  
Laboratory Scale ◽  
Kinetic Constants ◽  
Quantum Yields ◽  
Oxidation Of Methane ◽  
Oxygen Donor ◽  
Absorbed Power ◽  
Kinetics Of

Kinetics of photocatalytic oxidation of methane, ethane,n-heptane,n-decane, andn-dodecane, to yield intermediates, and photomineralisation of intermediates, to yield carbon dioxide and water, was studied in aqueous solution, by a laboratory-scale photoreactor and photocatalytic membranes immobilizing30±3wt.% ofTiO2, in the presence of stoichiometric hydrogen peroxide as oxygen donor. The whole volume of irradiated solution was4.000±0.005L, the ratio between this volume and the geometrical apparent surface of the irradiated side of the photocatalytic membrane was3.8±0.1cm, and the absorbed power 0.30W/cm (cylindrical geometry). A kinetic model was used, by which mineralisation of substrate toCO2was supposed to occur, by kinetic constantsk1, through one single intermediate, mediating the behaviour of all the numerous real intermediates formed in the path from the substrate toCO2(kinetic constants of formation of the latter beingk2). A competitive Langmuirian adsorption of both substrate and “intermediate” was also supposed to be operative, as expressed by apparent adsorption constantsk1andk2, possessing a, partly at least, kinetic significance. By Langmuir-Hinshelwood treatment of initial rate data, starting values of thekandKcouples were obtained, from which, by a set of differential equations, the final optimised parameters,k1andk1,k2andK2, were calculated, able fit the whole photomineralisation curve, and not only its initial segment, as the Langmuirian parameters do. The parameters of present work are critically compared with those obtained in two preceding set of studies relative ton-alkanoic acids and ton-alkanols. They are interpreted on the basis of a closer behaviour of hydrocarbons to alkanols, from the photocatalytic point of view, than to carboxylic acids are. Discussion of limiting effective quantum yields, and their comparison with maximum, theoretical values, are also carried out.

scholarly journals Rates and equilibrium constants for the covalent hydration of 5-bromo-2(1H)-pyrimidinone in aqueous solution

1986 ◽  
Vol 64 (6) ◽  
pp. 1267-1272 ◽  
Author(s):  
Oswald S. Tee ◽  
Jana Pika ◽  
M. Judith Kornblatt ◽  
Michael Trani
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Title Compound ◽  
Equilibrium Constants ◽  
Kinetic Studies ◽  
Kinetics Of

The kinetics of bromination of the title compound (1) have been measured in aqueous solutions of pH 0–6. The change in the order of reaction which occurs around pH 2.5 is explained by 1 reacting via its covalent hydrate, 3. Furthermore, there is sufficient 3 present at equilibrium that the kinetics of its equilibration with 1 were also measured. From these two studies the extent of covalent hydration of 1 is estimated to be 5%.Kinetic studies of the bromination of the dimethyl cation 5 and of its equilibration with the pseudobase 6 were also carried out for the purposes of comparison.The present results for 1, 3, 5, and 6 are compared to earlier results for 2-pyrimidinone and analogous derivatives.

Stability of the Nerve Gas Antidote BIS (4-Hydroxyiminomethyl-1-Pyridinomethyl) Ether Dichloride (Toxogonin®)

1968 ◽  
Vol 2 (9) ◽  
pp. 234-243 ◽  
Author(s):  
Inga Christenson
Keyword(s):  
Aqueous Solution ◽  
Hydrochloric Acid ◽  
Sodium Hydroxide ◽  
Rate Constants ◽  
Kinetics Of Hydrolysis ◽  
Dilute Aqueous Solution ◽  
Nerve Gas ◽  
Ph Range ◽  
Kinetics Of ◽  
Hydrolysis Of

The products and kinetics of hydrolysis of the nerve gas antidote bis(4-hydroxyiminomethyl - 1 - pyridinemethyl) ether dichloride (Toxogonin ®) have been investigated. A survey of these studies is given: The hydrolytic reactions were studied in the pH range 1 M hydrochloric acid to 1 M sodium hydroxide at 25, 45, 75 and 85° C. Rate constants were determined in dilute aqueous solution, generally with an initial Toxogonin concentration of 0.01 mg per ml. In addition, a report is given concerning two-year storage of 25 percent (w/v) Toxogonin solutions at pH 2.5, 3.0 and 3.5. The solutions were stored in glass or polypropylene ampuls at 5, 15, 25 and 45°C. At 5 and 15C° decomposition was negligible, at 25 and 45 °C average decomposition was 1.5 percent and 3.3 percent, respectively.

Kinetics of the Decomposition of Sulphur Dicyanide in Aqueous Solution

1962 ◽  
Vol 15 (2) ◽  
pp. 211 ◽  
Author(s):  
W Kitching ◽  
RH Smith ◽  
IR Wilson
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Nucleophilic Substitution ◽  
Perchloric Acid ◽  
Reaction Path ◽  
Acid Solutions ◽  
Kinetics Of

The kinetics and stoicheiometry of the decomposition of aqueous solutions of sulphur dicyanide have been studied at temperatures between 0-70 �C and in media ranging from dilute perchloric acid to pH 7. The predominant reaction is nucleophilic substitution at carbon, but in perchloric acid solutions an alternative reaction path has been revealed.

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.

scholarly journals A study of the kinetics and mechanism of rabbit muscle l-glycerol 3-phosphate dehydrogenase

1974 ◽  
Vol 143 (1) ◽  
pp. 19-27 ◽  
Author(s):  
Philip Bentley ◽  
F. Mark Dickinson
Keyword(s):  
Basic Mechanism ◽  
Kinetics And Mechanism ◽  
Dihydroxyacetone Phosphate ◽  
Rabbit Muscle ◽  
Kinetics Of Oxidation ◽  
Mechanism Of Catalysis ◽  
Glycerol 3 Phosphate Dehydrogenase ◽  
Ph Range ◽  
Kinetics Of

1. The kinetics of oxidation of l-glycerol 3-phosphate by NAD+and of reduction of dihydroxyacetone phosphate by NADH catalysed by rabbit muscle glycerol 3-phosphate dehydrogenase were studied over the range pH6–9. 2. The enzyme was found to catalyse the oxidation of glyoxylate by NAD+at pH8.0 and the kinetics of this reaction were also studied. 3. The results are consistent with a compulsory mechanism of catalysis for glycerol 3-phosphate oxidation and dihydroxyacetone phosphate reduction in the intermediate regions of pH, but modifications to the basic mechanism are required to fully explain results at the extremes of the pH range, with these substrates and for glyoxylate oxidation at pH8.0.

Amidoxime-functionalized hydrothermal carbon materials for uranium removal from aqueous solution

RSC Advances ◽  
2016 ◽  
Vol 6 (104) ◽  
pp. 102462-102471 ◽  
Author(s):  
Zhibin Zhang ◽  
Zhimin Dong ◽  
Ying Dai ◽  
Saijin Xiao ◽  
Xiaohong Cao ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
High Selectivity ◽  
Carbon Materials ◽  
Uranium Removal ◽  
Wide Ph Range ◽  
Ph Range

Amidoxime-functionalized hydrothermal carbon (AO-HTC) has been synthesized and applied to adsorb U(vi) from aqueous solutions, exhibiting a high selectivity above 60% for a wide pH range from 1.0 to 5.0.

Synthesis, Acid-Base Properties, Kinetics and Mechanism of Cu2+ Incorporation into Water-Soluble Highly Substituted Porphyrins

2017 ◽  
Vol 21 (09) ◽  
pp. 611-621
Author(s):  
Hirofumi Konno ◽  
Jun Takeda
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Kinetics And Mechanism ◽  
Water Soluble ◽  
Acid Base ◽  
Base Equilibrium ◽  
Absorbance Change ◽  
Acid Base Equilibrium ◽  
Kinetics Of ◽  
Base Properties

The synthesis, acid-base properties, and kinetics of Cu[Formula: see text] incorporation into water-soluble highly substituted porphyrins were studied. The basicity increased and the stepwise acid-base equilibrium was clarified by increasing the number of phenyl groups at the [Formula: see text] position, and the basicity of a dodeca-substituted porphyrin increased with the ionic strength. The metalation reaction of the dodeca-substituted porphyrin with Cu[Formula: see text] in aqueous solution revealed a biphasic absorbance change at 453 nm. Plots of [Formula: see text] or[Formula: see text] vs. the Cu[Formula: see text] concentration and of log ([Formula: see text] or[Formula: see text]/[Formula: see text] 0) vs. the ionic strength show that [Formula: see text] is dependent on the Cu[Formula: see text] concentration and ionic strength, while [Formula: see text] is independent of these parameters. These results confirm the stepwise metalation mechanism and the existence of an intermediate in aqueous solution, which is indicated by the biphasic absorbance change at 453 nm.

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