Nafion Perfluorinated Membranes Treated in Fenton Media:  Radical Species Detected by ESR Spectroscopy

2004 ◽  
Vol 108 (14) ◽  
pp. 4332-4337 ◽  
Author(s):  
Admira Bosnjakovic ◽  
Shulamith Schlick
Keyword(s):  
Esr Spectroscopy ◽  
Radical Species ◽  
Perfluorinated Membranes

ESR-Untersuchungen von Nitroxyl-Radikalen / ESR Studies of Nitroxyl Radicals

1976 ◽  
Vol 31 (9) ◽  
pp. 1265-1269 ◽  
Author(s):  
K. Scheffler ◽  
P. Schuler ◽  
G. Sosnovsky
Keyword(s):  
Exchange Rates ◽  
Exchange Interaction ◽  
Esr Spectroscopy ◽  
Esr Spectra ◽  
Nitroxyl Radicals ◽  
Radical Species ◽  
Fast Exchange ◽  
Theoretical Line ◽  
Multispin Systems ◽  
Line Positions

Mono-, di- and trinitroxylradicals are investigated in solution by ESR spectroscopy. The ESR spectra of all multispin systems studied can be interpreted under the assumption of an exchange interaction of the radical electrons. The exchange energies J are evaluated by comparison of experimental and theoretical line positions. The temperature dependence of J leads to activation energies around 1.5 Kcal/Mol. The analysis of proton hfs of the biradicals indicates the existence of two radical species which slow and fast exchange rates.

Electrochemical Reduction of AQ27DS in Aqueous Solution

2006 ◽  
Vol 514-516 ◽  
pp. 1338-1342
Author(s):  
César A.C. Sequeira ◽  
Rui F. M. Lobo ◽  
Giorgios Anastassakis
Keyword(s):  
Aqueous Solution ◽  
Esr Spectroscopy ◽  
Limiting Current ◽  
Disc Electrode ◽  
Rotating Disc ◽  
Radical Species ◽  
Sulphide Oxidation ◽  
Electrode Surfaces ◽  
Peak Separation ◽  
Anthraquinone Derivatives

It is known that anthraquinone derivatives act as aqueous sulphide oxidation catalysts, so the redox chemistry of the compound anthraquinone 2,7-disulphonate (AQ27DS) stimulated our interest, as reported here. AQ27DS was reduced in aqueous solution at pH 9.0 to give a deep red coloured air-sensitive solution. Cyclic voltammetry and exhaustive electrolysis indicated that the anthraquinone was reversibly reduced in a two electron, one proton process at a variety of electrode surfaces. From limiting current results at a rotating disc electrode, the diffusion coefficient of AQ27DS was calculated to be 3.37 x 10-10 m2 s-1. Spectroscopic results confirmed that AQ27DSH- was the major reduced species, but also indicated that the di-anion (AQ27DS2-) and radical species AQ27DS• were also present. ESR spectroscopy showed that the radical was formed via a comproportionation reaction between the di-anion and the AQ27DS starting material. The peak separation from voltammetry enabled the comproportionation constant (Kc) to be estimated, and it was found to be in the range of 0.4 to 4.

Structure and Reactions of Radicals Derived from Cyclopentane, Cyclopentenes, and Cyclohexenes in Low-Temperature Matrices. An ESR Study

1991 ◽  
Vol 46 (11) ◽  
pp. 993-1000 ◽  
Author(s):  
Yoshihiro Kubozono ◽  
Makoto Okada ◽  
Makoto Aoyagi ◽  
Shuichi Yahiro ◽  
Yasuhiko Gondo ◽  
...  
Keyword(s):  
Esr Spectroscopy ◽  
Hyperfine Coupling ◽  
Coupling Constants ◽  
Mo Calculations ◽  
Radical Species ◽  
Geometrical Structures ◽  
Frozen Solution ◽  
Semiempirical Mo Calculations ◽  
Γ Rays ◽  
Γ Ray

AbstractThe radical species derived from cyclopentane, cyclopentenes and cyclohexenes by 60Co γ-ray irradiation at 77 K in halocarbon matrices have been studied by ESR spectroscopy. The electronic and geometrical structures of the radical species are discussed on the basis of the experimental hyperfine coupling constants and semiempirical MO calculations. Exposure of the tetramethylsilane frozen solution containing cyclopentene to 60Co γ-rays produced specifically 3-cyclopenten-l-yl.

Kinetics of the Thermal Disappearance of Radicals Formed During the Radiolysis of Aspartic Acid

2009 ◽  
Vol 59 (12) ◽  
Author(s):  
Mihai Contineanu ◽  
iulia Contineanu ◽  
Ana Neacsu ◽  
Stefan Perisanu
Keyword(s):  
Thermal Resistance ◽  
Aspartic Acid ◽  
Room Temperature ◽  
Esr Spectra ◽  
Complex Mechanism ◽  
Radical Species ◽  
Mechanisms Of Formation ◽  
Kinetics Of

The radiolysis of the isomers L-, D- and DL- of the aspartic acid, in solid polycrystalline state, was investigated at room temperature. The analysis of their ESR spectra indicated the formation of at least two radicalic entities. The radical, identified as R3, resulting from the deamination of the acid, exhibits the highest concentration and thermal resistance. Possible mechanisms of formation of three radical species are suggested, based also on literature data. The kinetics of the disappearance of radical R3 indicated a complex mechanism. Three possible variants were suggested for this mechanism.

Electrochemical behaviour and ESR spectra of nitro substituted mono- and dibenzoylmethylenebenzthiazolines and selenazolines

1979 ◽  
Vol 44 (5) ◽  
pp. 1540-1551 ◽  
Author(s):  
Jaro Komenda ◽  
Jiří Huzlík
Keyword(s):  
Electron Transfer ◽  
Esr Spectroscopy ◽  
Electrochemical Behaviour ◽  
Spectroscopic Studies ◽  
Esr Spectra ◽  
Slow Electron

Compounds of the type of 2-(4'-nitrobenzoyl)methylene-3-ethylbenzothiazoline (I) and 2-bis-(p-nitrobenzoyl)methylene-3-ethylbenzothiazoline (II) were studied polarographically and by ESR spectroscopy to obtain informations about their electrochemical and follow-up reactions and their conformation. Whereas with compounds of the type I the conjugation in their molecules is preserved, with type II the coplanarity of the molecules is disturbed, which is manifested in the values of the splitting constants of the ESR spectra and a slow electron transfer between both nitrophenyl substituents. These conclusions are supported by NMR spectroscopic studies.

Association of radical anion with alkali cations. IV. ESR study of the 4-nitrobenzophenone radical anion

1980 ◽  
Vol 45 (2) ◽  
pp. 369-375 ◽  
Author(s):  
Stanislav Miertuš ◽  
Ondrej Kyseľ
Keyword(s):  
Hyperfine Splitting ◽  
Radical Anion ◽  
Esr Spectroscopy ◽  
Supporting Electrolyte ◽  
Esr Spectra ◽  
Proton Donor ◽  
Alkali Cations

The 4-nitrobenzophenone radical anion prepared by electrolysis was studied by ESR spectroscopy. On the basis of the interpretation of ESR spectra, the conformation of this system was estimated. The effect of the concentration of supporting electrolyte and of the presence of a proton-donor agent (C2H5OH) was examined. It is assumed that changes in hyperfine splitting constants are caused by association.

Stability of radical anions derived from substituted 5-nitrofurans investigated by ESR spectroscopy

1985 ◽  
Vol 50 (7) ◽  
pp. 1594-1601 ◽  
Author(s):  
Jiří Klíma ◽  
Larisa Baumane ◽  
Janis Stradinš ◽  
Jiří Volke ◽  
Romualds Gavars
Keyword(s):  
Radical Anion ◽  
High Stability ◽  
Esr Spectroscopy ◽  
Reaction Path ◽  
Order Reaction ◽  
Second Order ◽  
Radical Anions ◽  
Second Order Reaction ◽  
Unpaired Electron Density ◽  
The Stability

It has been found that the decay in dimethylformamide and dimethylformamide-water mixtures of radical anions in five of the investigated 5-nitrofurans is governed by a second-order reaction. Only the decay of the radical anion generated from 5-nitro-2-furfural III may be described by an equation including parallel first- and second-order reactions; this behaviour is evidently caused by the relatively high stability of the corresponding dianion, this being an intermediate in the reaction path. The presence of a larger conjugated system in the substituent in position 2 results in a decrease of the unpaired electron density in the nitro group and, consequently, an increase in the stability of the corresponding radical anions.

The effect of cation concentration on the nitrogen splitting constant of nitroxide free radicals

1990 ◽  
Vol 55 (10) ◽  
pp. 2377-2380
Author(s):  
Hamza A. Hussain
Keyword(s):  
Hydrogen Peroxide ◽  
Hydrogen Bonding ◽  
Free Radicals ◽  
Esr Spectroscopy ◽  
The Other ◽  
Tetraethylammonium Bromide ◽  
Splitting Constant ◽  
The One ◽  
Positively Charged ◽  
Two Equilibria

Nitroxide free radicals prepared from diethylamine, piperidine and pyrrolidine by oxidation with hydrogen peroxide were studied by ESR spectroscopy. The changes in the 14N splitting constant (aN) caused by the addition of KBr or tetraethylammonium bromide were measured in dependence on the concentration of the ions. For diethylamine nitroxide and piperidine nitroxide, the results are discussed in terms of two equilibria: the one, involving the anion, is associated with a gain or loss of hydrogen bonds to the nitroxide oxygen atom, the other is associated with the formation of solvent shared units involving the cation, which results in changes in the hydrogen bonding strenght. The large increase in the aN value in the case of pyrrolidine nitroxide is explained in terms of an interaction from one side of the positively charged N atom; the increase in aN in the case of diethylamine and piperidine nitroxides is explained in terms of interactions with both sides of the positively charged N atom.

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