A new kinetic approach to the evaluation of rate constants for the spin trapping of superoxide/hydroperoxyl radical by nitrones in aqueous media

2004 ◽  
Vol 2 (9) ◽  
pp. 1304 ◽  
Author(s):  
Robert Lauricella ◽  
Ahmad Allouch ◽  
Val�rie Roubaud ◽  
Jean-Claude Bouteiller ◽  
B�atrice Tuccio
Keyword(s):  
Rate Constants ◽  
Aqueous Media ◽  
Spin Trapping ◽  
Kinetic Approach ◽  
Hydroperoxyl Radical

Studies in polymerization XI. Reactions between polymer radicals and ferric chloride in non-aqueous media

1957 ◽  
Vol 239 (1217) ◽  
pp. 214-229 ◽  
Keyword(s):  
Electron Transfer ◽  
Ferric Chloride ◽  
Rate Constants ◽  
Aqueous Media ◽  
Practical Method ◽  
General Treatment ◽  
Ferrous Chloride ◽  
Styrene Polymerization ◽  
Induction Periods ◽  
Dimethylformamide Solution

The polymerizations of acrylonitrile, methacrylonitrile and styrene have been studied in NN -dimethylformamide solution at 60°C in the presence of ferric chloride. In each case the participating radicals enter into a termination reaction with the salt, with reduction of the latter to ferrous chloride. The rate constants of these reactions have been evaluated from kinetic observations; styryl radicals are much more reactive towards ferric chloride than either acrylonitrile or methacrylonitrile radicals. This is the expected order if the reactions are of the electron-transfer type. It is shown that estimation of the ferrous salt produced provides a useful practical method for determining the rate of chain starting. In the case of styrene, the reactivity of the radicals is so great that induction periods are observed, from which the rates of chain starting may also be deduced. A general treatment of retarded reactions under certain simple conditions is given and applied to the styrene polymerization.

Hydrogen Isotope Exchange in 2-Butanone. Further Measurements and Some Comments

1972 ◽  
Vol 50 (19) ◽  
pp. 3239-3241 ◽  
Author(s):  
R. A. Cox ◽  
J. W. Thorpe ◽  
J. Warkentin
Keyword(s):  
Acetic Acid ◽  
Temperature Dependence ◽  
Rate Constants ◽  
Hydrogen Isotope ◽  
Isotope Exchange ◽  
Relative Rate ◽  
Aqueous Media ◽  
Acetate Buffer ◽  
Isokinetic Temperature ◽  
Relative Rate Constants

The ratio of rate constants for exchange at the methylene and methyl positions of butanone, [Formula: see text], is shown to be near 1.69 in 1:1 acetic acid–acetate buffer; nearly twice the value (0.86) for deuterioxide catalysis at 54.8°. Methods of obtaining rate constants for acetate catalysis from composite rates (acetate and deuterioxide), or from rates in buffered media, are shown to be adequate for estimating rate ratios.Detailed temperature dependence of the relative rate constants for either system is not yet available but the effects are known to be small. For butanone enolizations the isokinetic temperature is in the neighborhood of 35°, when reaction is catalyzed by deuterioxide in aqueous media.

Formation and nucleophilic capture of N-nitrosiminium ions

1999 ◽  
Vol 77 (5-6) ◽  
pp. 1148-1161 ◽  
Author(s):  
Latifa Chahoua ◽  
Alain Vigroux ◽  
Yvonne Chiang ◽  
James C Fishbein
Keyword(s):  
Ionic Strength ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Aqueous Media ◽  
Laser Flash ◽  
Azide Ion ◽  
Iminium Ions ◽  
Nucleophilic Trapping

A study of the solvolysis of a series of (N-nitrosomethylamino)arylmethyl esters and azides and the products of nucleophilic trapping of the corresponding N-nitrosiminium ion intermediates in aqueous media, 25°C, ionic strength 1 M is reported. Structure-reactivity data for the forward and reverse reactions have been obtained. In three cases, the rate constants for reactions of the cations with nucleophiles have been measured directly by laser flash photolysis. The data allow a comparison of the degree to which the N-methyl-N-nitroso functionality enhances cation stability from a thermodynamic and kinetic perspective. It has been possible to deduce that the carbon basicity of azide ion is less than 1 kcal/mol greater than that of acetate ion.Key words: nitrosiminium ions, α-acetoxynitrosamines, carbocations, iminium ions, nucleophilicity.

scholarly journals Embedding cyclic nitrone in mesoporous silica particles for EPR spin trapping of superoxide and other radicals

The Analyst ◽  
2019 ◽  
Vol 144 (14) ◽  
pp. 4194-4203 ◽  
Author(s):  
Eric Besson ◽  
Stéphane Gastaldi ◽  
Emily Bloch ◽  
Jacek Zielonka ◽  
Monika Zielonka ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Radical Anion ◽  
Superoxide Radical ◽  
Spin Trap ◽  
Aqueous Media ◽  
Spin Trapping ◽  
Silica Particles ◽  
Superoxide Radical Anion ◽  
Wide Range ◽  
Epr Spin Trapping

Mesoporous silica functionalised with a cyclic spin trap enabled the identification of a wide range of radicals in organic and aqueous media, including superoxide radical anion.

Rate constants for reactions of ethylbenzene with hydroperoxyl radical

2013 ◽  
Vol 160 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Mohammednoor Khalil Altarawneh ◽  
Bogdan Z. Dlugogorski ◽  
Eric M. Kennedy ◽  
John C. Mackie
Keyword(s):  
Rate Constants ◽  
Hydroperoxyl Radical

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

1978 ◽  
Vol 56 (23) ◽  
pp. 2970-2976 ◽  
Author(s):  
Oswald S. Tee ◽  
David C. Thackray ◽  
Charles G. Berks
Keyword(s):  
Kinetic Study ◽  
Rate Constants ◽  
Aqueous Media ◽  
Stopped Flow ◽  
Flow Method ◽  
High Acidity ◽  
Rate Determining Step ◽  
Kinetics Of ◽  
Good Agreement

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.

The photodegradation of model quinolone carboxylates in aqueous media

2014 ◽  
Vol 7 (1) ◽  
pp. 1-8
Author(s):  
Miroslava Bobeničová ◽  
Andrea Čaklóšová ◽  
Dana Dvoranová
Keyword(s):  
Titanium Dioxide ◽  
Hydroxyl Radicals ◽  
Aqueous Media ◽  
Spin Trapping ◽  
Alkaline Media ◽  
Uva Irradiation ◽  
Epr Spin Trapping ◽  
Photoinduced Processes

Abstract This work was focused on the study of photoinduced processes of quinolone carboxylates in the presence of titanium dioxide in an alkaline media. UVA irradiation without/with titanium dioxide caused the decomposition of molecules, with higher efficiency of degradation in the presence of titanium dioxide. EPR spin trapping experiments proved that investigated quinolone carboxylates behave as the efficient scavengers of hydroxyl radicals produced upon irradiation of aerated alkaline titanium dioxide systems.

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