Bimolecular Rate Constant Determination for the Reaction of Hydroxyl Radicals with Domoic and Kainic Acid in Aqueous Solution

2009 ◽  
Vol 43 (17) ◽  
pp. 6764-6768 ◽  
Author(s):  
Kimberly G. Jones ◽  
William J. Cooper ◽  
Stephen P. Mezyk
Keyword(s):  
Aqueous Solution ◽  
Kainic Acid ◽  
Hydroxyl Radicals ◽  
Rate Constant ◽  
Bimolecular Rate Constant ◽  
Constant Determination

Determination of the Bimolecular Rate Constant of Polyacrylamide and Hydroxyl Radicals

2015 ◽  
Vol 44 (2) ◽  
pp. 220-222
Author(s):  
Sonia N. Nomi ◽  
Yumi Higaonna ◽  
Tomoha Kasaba ◽  
Takemitsu Arakaki
Keyword(s):  
Hydroxyl Radicals ◽  
Rate Constant ◽  
Bimolecular Rate Constant

Photooxidation of 1,3-butadiene containing systems: Rate constant determination for the reaction of acrolein with?OH radicals

1980 ◽  
Vol 12 (12) ◽  
pp. 905-913 ◽  
Author(s):  
Andrea Maldotti ◽  
Claudio Chiorboli ◽  
Carlo A. Bignozzi ◽  
Carlo Bartocci ◽  
Vittorio Carassiti
Keyword(s):  
Rate Constant ◽  
Oh Radicals ◽  
Constant Determination

Critical Review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals (⋅OH/⋅O− in Aqueous Solution

1988 ◽  
Vol 17 (2) ◽  
pp. 513-886 ◽  
Author(s):  
George V. Buxton ◽  
Clive L. Greenstock ◽  
W. Phillips Helman ◽  
Alberta B. Ross
Keyword(s):  
Aqueous Solution ◽  
Hydroxyl Radicals ◽  
Rate Constants ◽  
Critical Review ◽  
Hydrogen Atoms ◽  
Hydrated Electrons

THE OXIDATION OF NITRITE AND IODATE IONS BY HYPOCHLORITE IONS

1961 ◽  
Vol 39 (8) ◽  
pp. 1645-1651 ◽  
Author(s):  
M. W. Lister ◽  
P. Rosenblum
Keyword(s):  
Activation Energy ◽  
Aqueous Solution ◽  
Rate Constant ◽  
Hypochlorous Acid ◽  
Slow Stage ◽  
Iodate Ions

The oxidation of nitrite ions and of iodate ions by hypochlorite ions in aqueous solution has been examined. The oxidation of nitrite is really a reaction of hypochlorous acid, with the slow stage HOCl + NO2− + H2O → H3O+ + Cl− + NO3−. The rate constant is given by log k = 7.36−6450/RT (time in minutes, and the activation energy in calories). The oxidation of iodate is chiefly a reaction of hypochlorite ions, probably ClO− + IO3− → Cl− + IO4−, although the rate is somewhat increased by a higher concentration of hydroxide ions. The rate constant is given by log k = 16.15−26,100/RT. These results are compared with other oxidations by hypochlorite ions, to see if any general trends are apparent.

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.

Photochemistry of acetylene. Bimolecular rate constant for the formation of butadiyne and reactions of ethynyl radicals

1979 ◽  
Vol 83 (3) ◽  
pp. 310-313 ◽  
Author(s):  
Allan H. Laufer ◽  
Arnold M. Bass
Keyword(s):  
Rate Constant ◽  
Bimolecular Rate Constant

scholarly journals Photochemical Degradation of Sulfadiazine

2013 ◽  
Vol 39 (3) ◽  
pp. 79-91 ◽  
Author(s):  
Natalia Lemańska-Malinowska ◽  
Ewa Felis ◽  
Joanna Surmacz-Górska
Keyword(s):  
Hydrogen Peroxide ◽  
Uv Radiation ◽  
Hydroxyl Radicals ◽  
Rate Constant ◽  
Photochemical Degradation ◽  
Photochemical Processes

Abstract The photochemical degradation of the sulfadiazine (SDZ) was studied. The photochemical processes used in degradation of SDZ were UV and UV/H2O2. In the experiments hydrogen peroxide was applied at different concentrations: 10 mg/dm3 (2.94*10-4 M), 100 mg/dm3 (2.94*10-3 M), 1 g/dm3 (2.94*10-2 M) and 10 g/dm3 (2.94*10-1 M). The concentrations of SDZ during the experiment were controlled by means of HPLC. The best results of sulfadiazine degradation, the 100% removal of the compound, were achieved by photolysis using UV radiation in the presence of 100 mg H2O2/dm3 (2.94*10-3 M). The determined rate constant of sulfadiazine reaction with hydroxyl radicals kOH was equal 1.98*109 M-1s-1.

scholarly journals Antioxidant activity of Induna apple pomace extract

2005 ◽  
pp. 239-246 ◽  
Author(s):  
Sladjana Savatovic ◽  
Sonja Djilas ◽  
Vesna Tumbas ◽  
Jasna Canadanovic-Brunet ◽  
Gordana Cetkovic
Keyword(s):  
Aqueous Solution ◽  
Antioxidant Activity ◽  
Acetic Acid ◽  
Electron Spin Resonance ◽  
Hydroxyl Radicals ◽  
Electron Spin ◽  
Esr Spectroscopy ◽  
Methanol Extract ◽  
Apple Pomace ◽  
Spin Resonance

Different concentrations ofmethanol aqueous solution with or without 0.5% acetic acid and 80% acetone were used to achieve the highest yield of extraction of phenolics from Induna apple pomace. The highest content of phenolics (6.38 mg/g) was detected in the 80% methanol extract. The influence of 80% methanol extract of Induna apple pomace on stable l,l-diphenyl-2-picrylhydrazyl (DPPH) and reactive hydroxyl radicals has been investigated by electron spin resonance (ESR) spectroscopy. Based on the obtained results it can be concluded that the investigated extract is more effective in the DPPH test than on the DMPO-OH scavenging. In both cases antioxidant activity increased with increasing concentration of the investigated extract. The high contents ofphenolics (6.38 mg/g), flavonoids (1.01 mg/g) and flavan-3-ols (0.70 mg/g) in 80% methanol extract indicated that these compounds contributed to the antioxidant activity of Induna apple pomace.

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