Abstraction of Hydrogen from Methanol by Hydroxyl Radical in Subcritical and Supercritical Water

2003 ◽  
Vol 107 (50) ◽  
pp. 11043-11048 ◽  
Author(s):  
Junbo Feng ◽  
Sudhir N. V. K. Aki ◽  
John E. Chateauneuf ◽  
Joan F. Brennecke
Keyword(s):  
Hydroxyl Radical ◽  
Supercritical Water

Hydroxyl Radical Reactivity with Nitrobenzene in Subcritical and Supercritical Water

2002 ◽  
Vol 124 (22) ◽  
pp. 6304-6311 ◽  
Author(s):  
Junbo Feng ◽  
Sudhir N. V. K. Aki ◽  
John E. Chateauneuf ◽  
Joan F. Brennecke
Keyword(s):  
Hydroxyl Radical ◽  
Supercritical Water ◽  
Radical Reactivity ◽  
Hydroxyl Radical Reactivity

Hydroxyl radical reactions with 2-chlorophenol as a model for oxidation in supercritical water

2013 ◽  
Vol 40 (3) ◽  
pp. 973-990 ◽  
Author(s):  
Jiaming Zhang ◽  
Chunyuan Ma ◽  
Youmin Sun ◽  
Xiaohua Ren
Keyword(s):  
Hydroxyl Radical ◽  
Supercritical Water ◽  
Radical Reactions

Activation of cytochrome c to a peroxidase compound I-type intermediate by H2O2: relevance to redox signalling in apoptosis

2004 ◽  
Vol 71 ◽  
pp. 97-106 ◽  
Author(s):  
Mark Burkitt ◽  
Clare Jones ◽  
Andrew Lawrence ◽  
Peter Wardman
Keyword(s):  
Cytochrome C ◽  
Hydroxyl Radical ◽  
Redox Regulation ◽  
Chemotherapeutic Agents ◽  
Tyrosyl Radical ◽  
Compound I ◽  
Definitive Evidence ◽  
Enhanced Production ◽  
Physico Chemical

The release of cytochrome c from mitochondria during apoptosis results in the enhanced production of superoxide radicals, which are converted to H2O2 by Mn-superoxide dismutase. We have been concerned with the role of cytochrome c/H2O2 in the induction of oxidative stress during apoptosis. Our initial studies showed that cytochrome c is a potent catalyst of 2′,7′-dichlorofluorescin oxidation, thereby explaining the increased rate of production of the fluorophore 2′,7′-dichlorofluorescein in apoptotic cells. Although it has been speculated that the oxidizing species may be a ferryl-haem intermediate, no definitive evidence for the formation of such a species has been reported. Alternatively, it is possible that the hydroxyl radical may be generated, as seen in the reaction of certain iron chelates with H2O2. By examining the effects of radical scavengers on 2′,7′-dichlorofluorescin oxidation by cytochrome c/H2O2, together with complementary EPR studies, we have demonstrated that the hydroxyl radical is not generated. Our findings point, instead, to the formation of a peroxidase compound I species, with one oxidizing equivalent present as an oxo-ferryl haem intermediate and the other as the tyrosyl radical identified by Barr and colleagues [Barr, Gunther, Deterding, Tomer and Mason (1996) J. Biol. Chem. 271, 15498-15503]. Studies with spin traps indicated that the oxo-ferryl haem is the active oxidant. These findings provide a physico-chemical basis for the redox changes that occur during apoptosis. Excessive changes (possibly catalysed by cytochrome c) may have implications for the redox regulation of cell death, including the sensitivity of tumour cells to chemotherapeutic agents.

Activities of antioxidant enzymes and nitric oxide synthase, hydroxyl radical and zinc contents in gastric mucosa cells during the recovery of stress-induced stomach lesions

2008 ◽  
Vol 21 (1) ◽  
pp. 215-217
Author(s):  
Olena Bogdanova ◽  
Larysa Kot ◽  
Dmytro Lukashov ◽  
Ludmyla Ostapchenko
Keyword(s):  
Nitric Oxide ◽  
Antioxidant Enzymes ◽  
Nitric Oxide Synthase ◽  
Gastric Mucosa ◽  
Hydroxyl Radical ◽  
Oxide Synthase

A Systematic DFT Study of Two Elementary Steps Involving Hydrogen Peroxide and the Hydroxyl Radical in the Fenton Reaction

2018 ◽  
Author(s):  
Danilo Carmona ◽  
David Contreras ◽  
Oscar A. Douglas-Gallardo ◽  
Stefan Vogt-Geisse ◽  
Pablo Jaque ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Ab Initio ◽  
Fenton Reaction ◽  
Basis Set ◽  
Basis Sets ◽  
Dft Methods ◽  
Elementary Steps ◽  
Oxygen Oxygen ◽  
Complete Basis Set

The Fenton reaction plays a central role in many chemical and biological processes and has various applications as e.g. water remediation. The reaction consists of the iron-catalyzed homolytic cleavage of the oxygen-oxygen bond in the hydrogen peroxide molecule and the reduction of the hydroxyl radical. Here, we study these two elementary steps with high-level ab-initio calculations at the complete basis set limit and address the performance of different DFT methods following a specific classification based on the Jacob´s ladder in combination with various Pople's basis sets. Ab-initio calculations at the complete basis set limit are in agreement to experimental reference data and identified a significant contribution of the electron correlation energy to the bond dissociation energy (BDE) of the oxygen-oxygen bond in hydrogen peroxide and the electron affinity (EA) of the hydroxyl radical. The studied DFT methods were able to reproduce the ab-initio reference values, although no functional was particularly better for both reactions. The inclusion of HF exchange in the DFT functionals lead in most cases to larger deviations, which might be related to the poor description of the two reactions by the HF method. Considering the computational cost, DFT methods provide better BDE and EA values than HF and post--HF methods with an almost MP2 or CCSD level of accuracy. However, no systematic general prediction of the error based on the employed functional could be established and no systematic improvement with increasing the size in the Pople's basis set was found, although for BDE values certain systematic basis set dependence was observed. Moreover, the quality of the hydrogen peroxide, hydroxyl radical and hydroxyl anion structures obtained from these functionals was compared to experimental reference data. In general, bond lengths were well reproduced and the error in the angles were between one and two degrees with some systematic trend with the basis sets. From our results we conclude that DFT methods present a computationally less expensive alternative to describe the two elementary steps of the Fenton reaction. However, choice of approximated functionals and basis sets must be carefully done and the provided benchmark allows a systematic validation of the electronic structure method to be employed

PENGGUNAAN AIR SUPER KRITIS PADA DEPOLIMERISASI NYLON-12 (BATCH PROCESS)

2018 ◽  
Vol 5 (3) ◽  
Author(s):  
Mohamad Yusman
Keyword(s):  
Supercritical Water ◽  
Scale Up ◽  
Experimental Studies ◽  
Reaction System ◽  
Batch Process ◽  
Chemical Recycling ◽  
Water Decomposition ◽  
Product Distributions ◽  
New Process ◽  
Nylon 12

Water at the supercritical state is a new process for the chemical recycling. At this thermodynamic state i.e. Pc = 218 atmospheres and Tc = 374oC , water behaves very differently from its everyday temperament and it is a very good solvent for organic components. Experimental studies show that supercritical water can decompose hydrocarbons/polymers and produce useful products like 2-Azacyclotridecanone /lactam-1 from Nylon-12 (batch process). The decomposition process itself was carried out in batch reaction system in order to get more information about product distributions, time dependence, and scale-up possibilities.Keywords: supercritical water, decomposition, batch, polymer, hydrocarbon

Kinetics of Supercritical Water Oxidation. SERDP Compliance Technical Thrust Area

1996 ◽  
Author(s):  
Steven F. Rice ◽  
Richard R. Steeper ◽  
Russell G. Hanush ◽  
Jason D. Aiken ◽  
Eric Croiset
Keyword(s):  
Supercritical Water ◽  
Water Oxidation ◽  
Supercritical Water Oxidation ◽  
Kinetics Of
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