Phenoxyl Radical Complexes

2002 ◽  
pp. 151-216 ◽  
Author(s):  
Phalguni Chaudhuri ◽  
Karl Wieghardt
Keyword(s):  
Phenoxyl Radical

ChemInform Abstract: REARRANGEMENT IN THE FREE PHENOXYL RADICAL OF THE CARBORANE SERIES

1978 ◽  
Vol 9 (14) ◽  
Author(s):  
V. B. PANOV ◽  
E. P. IVAKHNENKO ◽  
O. YU. OKHLOBYSTIN
Keyword(s):  
Phenoxyl Radical

scholarly journals Hydroxycinnamic Acid Antioxidants: An Electrochemical Overview

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
José Teixeira ◽  
Alexandra Gaspar ◽  
E. Manuela Garrido ◽  
Jorge Garrido ◽  
Fernanda Borges
Keyword(s):  
Rational Design ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Phenoxyl Radical ◽  
Free Radical Scavenger ◽  
Hydroxycinnamic Acid ◽  
Hydroxycinnamic Acids ◽  
Radical Scavenger ◽  
Redox Potentials ◽  
Structure Property

Hydroxycinnamic acids (such as ferulic, caffeic, sinapic, andp-coumaric acids) are a group of compounds highly abundant in food that may account for about one-third of the phenolic compounds in our diet. Hydroxycinnamic acids have gained an increasing interest in health because they are known to be potent antioxidants. These compounds have been described as chain-breaking antioxidants acting through radical scavenging activity, that is related to their hydrogen or electron donating capacity and to the ability to delocalize/stabilize the resulting phenoxyl radical within their structure. The free radical scavenger ability of antioxidants can be predicted from standard one-electron potentials. Thus, voltammetric methods have often been applied to characterize a diversity of natural and synthetic antioxidants essentially to get an insight into their mechanism and also as an important tool for the rational design of new and potent antioxidants. The structure-property-activity relationships (SPARs) correlations already established for this type of compounds suggest that redox potentials could be considered a good measure of antioxidant activity and an accurate guideline on the drug discovery and development process. Due to its magnitude in the antioxidant field, the electrochemistry of hydroxycinnamic acid-based antioxidants is reviewed highlighting the structure-property-activity relationships (SPARs) obtained so far.

From Reduction to Oxidation: pH Controlled Reaction of 1 Hydroxyethyl Radical with Caffeic Acid Analogues.

2021 ◽  
Vol 11 ◽  
Author(s):  
Laboni Das ◽  
Shashi P Shukla ◽  
Suchandra Chatterjee ◽  
Ashis K Satpati ◽  
Soumyakanti Adhikari
Keyword(s):  
Caffeic Acid ◽  
Rate Constant ◽  
Reduction Process ◽  
Phenoxyl Radical ◽  
Alpha Tocopherol ◽  
Side Chain ◽  
Product Analysis ◽  
Bimolecular Rate Constant ◽  
Ethyl Radical ◽  
Computational Calculations

Aims: The aim is to search for newer and better antioxidants through kinetic spectroscopic studies in combination with product analysis and computation. Background: Antioxidant effect of caffeic acid, its derivative, and analogues have been well reported. The antioxidative efficiencies are related to their molecular structure, and two reaction pathways are well accepted, H-atom transfer (HAT) or single electron transfer. 1-hydroxy ethyl radical (1-HER) being an ethanol-derived free radical might be causing the onset of liver injury detected after alcohol administration. 1-HER has also been reported to react with fatty acids and endogenous antioxidants such as glutathione, ascorbic acid, and alpha-tocopherol Objective: The present study is an attempt to understand the reaction mechanism of 1-HER with caffeic acid, its derivative, and analogues in detail. Method: Pulse radiolysis with kinetic absorption spectroscopy has been employed to follow the reaction pathway and identify the intermediates produced in the reaction. The reaction products have been detected using LCMS/MS. Based on these studies, a consolidated mechanism has been proposed. Cyclic voltammetry measurements and computational calculations have been used in support of the proposed mechanism. Result: In the reaction of 1-hydroxy ethyl radical (1-HER) with caffeic acid and its oligomers, reduction takes place below the pKa1, while oxidation occurs with the deprotonated phenolic moiety. The reduction of caffeic acid generates a carbon-centered radical at the double bond of the side chain with a bimolecular rate constant of 1.5x1010 dm3 mol-1 s-1. Notably, a low concentration of oxygen was able to regenerate a part of the caffeic acid molecules in the reduction process. At pH 10 a phenoxyl radical is formed due to oxidation with a much lower bimolecular rate constant (4.2x108 dm3 mol-1 s-1). In the case of di-hydrocaffeic acid, only phenoxyl radical is formed at pH 10 and, no reaction could be observed below pH 8. Conclusion: Change in reactive pattern from reduction to oxidation with change in pH within the same set of reactants has been evidently established in the present study. The results point towards the importance of  unsaturation in the side chain of caffeic acid oligomers for their reaction with 1-HER at neutral pH. The effect of oxygen concentration on the antioxidative protection offered by this class of molecules might be intriguing for the quest of the effectiveness of antioxidants at low concentrations. Other: It may be inferred that the effect of pH on the reactivity pattern as observed is not 1-HER, but substrate-specific, in the present case, phenolic acids. This study generates further scope for in-depth studies on other polyphenols where unsaturation exists in the side chain.

Oxidation of bisbenzenechromium(0) by stable phenoxyl radical

1978 ◽  
Vol 27 (3) ◽  
pp. 618-619
Author(s):  
A. Yu. Sorokin ◽  
Yu. A. Shevelev ◽  
G. A. Domrachev
Keyword(s):  
Phenoxyl Radical ◽  
Stable Phenoxyl

Reversible Solution π-Dimerization and Long Multicenter Bonding in a Stable Phenoxyl Radical

2018 ◽  
Vol 24 (56) ◽  
pp. 14906-14910 ◽  
Author(s):  
Nico M. Bonanno ◽  
Prashanth K. Poddutoori ◽  
Kazunobu Sato ◽  
Kenji Sugisaki ◽  
Takeji Takui ◽  
...  
Keyword(s):  
Phenoxyl Radical ◽  
Stable Phenoxyl ◽  
Multicenter Bonding
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