Properties of electrochemically generated primary anion radicals of 2,5-dimethyl-1-nitrophenylpyrroles

1981 ◽  
Vol 46 (10) ◽  
pp. 2494-2502 ◽  
Author(s):  
Pavel Kubáček
Keyword(s):  
Nitrogen Atom ◽  
Carbon Atom ◽  
Anion Radical ◽  
Platinum Electrode ◽  
Spin Population ◽  
Kinetics Of Decomposition ◽  
Primary Anion ◽  
Stable Anion ◽  
Kinetics Of ◽  
Anion Radicals

The first step of electrochemical reduction of 2,5-dimethyl-1-nitrophenylpyrroles on a platinum electrode in anhydrous acetonitrile consists in an one-electron process producing relatively stable anion radicals. The prediction based on HMO calculations concerning an almost complete localization of the LFMO in the nitrophenyl part of the studied molecules is fully confirmed by means of EPR spectroscopy. Magnitude of the found proton splitting constants is very close to the values found for anion radical of nitrobenzene. The splitting by nucleus of nitrogen atom of pyrrole cycle can be explained exclusively by the mechanism of π-σ spin polarization of σ C-N bond and by the spin population at the carbon atom. The EPR method has also been used for following the kinetics of decomposition of anion radicals of the molecules studied.

scholarly journals Reactions of Aromatic Anion Radicals and Dianions. IX. The Preparation of Stable Anion Radical Solutions Containing Tetra-alkylammonium Ions.

1978 ◽  
Vol 32b ◽  
pp. 510-514 ◽  
Author(s):  
Robert Lines ◽  
Bo Svensmark Jensen ◽  
Vernon D. Parker ◽  
Michael Sponholtz ◽  
Takao Matsuno
Keyword(s):  
Anion Radical ◽  
Stable Anion ◽  
Anion Radicals

Substituent effects in the reaction of aromatic amines and peroxydisulfate

1969 ◽  
Vol 47 (19) ◽  
pp. 3710-3713 ◽  
Author(s):  
N. Venkatasubramanian ◽  
A. Sabesan
Keyword(s):  
Nitrogen Atom ◽  
Carbon Atom ◽  
Aromatic Amines ◽  
Substituent Effects ◽  
Substituted Anilines ◽  
Electrophilic Attack ◽  
Effect Of Substituents ◽  
Hammett Constants ◽  
Kinetics Of ◽  
Electron Withdrawing Substituents

The kinetics of the reaction between aromatic amines and the peroxydisulfate ion in aqueous basic conditions have been investigated. The effect of substituents has been studied by employing about 25 ortho-, meta-, and para-substituted anilines. The reaction is accelerated by electron-releasing substituents and is retarded by electron-withdrawing substituents, pointing to an electrophilic attack by the S2O82− ion. A better correlation between rate and the Hammett constants is obtained for an electrophilic attack at the nitrogen atom of the amine rather than at the carbon atom of the amine. A good correlation also exists between the log k2 values and the pKb of the corresponding amines.

Electrochemical reduction of para-substituted 2-acyl-5-phenylfuranes in dimethylformamide

1981 ◽  
Vol 46 (2) ◽  
pp. 498-502 ◽  
Author(s):  
Jozef Černák ◽  
František Tomanovič ◽  
Andrej Staško ◽  
Anna Fedosyevna Oleinikova ◽  
Jaroslav Kováč
Keyword(s):  
Electrochemical Reduction ◽  
Unpaired Electron ◽  
Anion Radical ◽  
Electron Wave ◽  
Epr Method ◽  
Electron Center ◽  
Nitrogen Nucleus ◽  
Nitro Derivatives ◽  
Stable Anion ◽  
Derivatives Of

para Substituted chloro, bromo, and nitro derivatives of 2-acyl-5-phenylfurane are reduced polarographically in a one-electron wave to the corresponding anion radicals, which were studied by the EPR method. The reduction of nitro derivatives, studied by the Kalousek switch, is reversible and leads to a stable anion radical with an unpaired electron center on the nitrogen nucleus; the reduction of the halogen derivatives is only partly reversible and leads to unstable ketyl radicals. The bromo derivatives give polarographic maxima typical for concurrent reactions.

Kinetics and Mechanism of Decomposition of 1,3-Bis(4-methylphenyl)triazene Catalyzed with Substituted Benzoic Acids in 25% Aqueous Methanol-General or Specific Catalysis?

1994 ◽  
Vol 59 (9) ◽  
pp. 2029-2041
Author(s):  
Oldřich Pytela ◽  
Taťjana Nevěčná
Keyword(s):  
Benzoic Acids ◽  
Hammett Equation ◽  
Aqueous Methanol ◽  
Mechanism Of Decomposition ◽  
Kinetics Of Decomposition ◽  
Independent Variable ◽  
Amino Derivatives ◽  
Substituted Benzoic Acids ◽  
The Individual ◽  
Kinetics Of

The kinetics of decomposition of 1,3-bis(4-methylphenyl)triazene catalyzed with 13 substituted benzoic acids of various concentrations have been measured in 25 vol.% aqueous methanol at 25.0 °C. The rate constants observed (297 data) have be used as values of independent variable in a series of models of the catalyzed decomposition. For the catalytic particles were considered the undissociated acid, its conjugated base, and the proton in both the specific and general catalyses. Some models presumed formation of reactive or nonreactive complexes of the individual reactants. The substituent effect is described by the Hammett equation. The statistically best model in which the observed rate constant is a superposition of a term describing the dependence on proton concentration and a term describing the dependence on the product of concentrations of proton and conjugated base is valid with the presumption of complete proton transfer from the catalyst acid to substrate, which has been proved. The behaviour of 4-dimethylamino, 4-amino, and 3-amino derivatives is anomalous (lower catalytic activity as compared with benzoic acid). This supports the presumed participation of conjugated base in the title process.

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