Search results for "OXIDATION"
showing 10 items of 1913 documents
Photooxidation and Stabilization of Photooxidized Polyethylene and of its Monopolymer Blends
2003
The increasing use of products from recycled polymers, or from blends with recycled polymers exposed to the outdoors, implies the need for good weathering resistance. This is particularly important when the recycled material comes, in turn, from products exposed during their lifetime to the sun. In this case the presence of C=O groups in the macromolecular chains strongly increases the photooxidative degradation kinetics of these secondary materials. In this work the change of the photooxidative degradation of blends of virgin and photooxidized polyethylene was evaluated as a function of the C=O content present in the material. As expected, the presence of the C=O groups strongly increases …
ChemInform Abstract: A Simple Procedure for the Oxidation of Alcohols Using [Bis(acetoxy)iodo]benzene and a Catalytic Amount of Bromide Ions in Ethyl…
2015
Primary and secondary benzylic alcohols and secondary aliphatic alcohols were oxidized to the corresponding aldehydes and ketones by using [bis(acetoxy)iodo]benzene (BAIB) and a catalytic amount of bromide ions, from tetrabutylammonium bromide or KBr, in ethyl acetate. The catalytic role of the bromide ions was also highlighted in the oxidation of primary aliphatic alcohols and secondary allylic alcohols carried out in the presence of 1 mol% TEMPO.
[23] Ratio of reduced to oxidized glutathione as indicator of oxidative stress status and DNA damage
1999
Publisher Summary This chapter discusses the ratio of reduced to oxidized glutathione (GSH) as an indicator of oxidative stress status and DNA damage. Several methods have been proposed for the determination of GSH status in biological samples. Accurate determination of this status is largely dependent on the prevention of GSH autoxidation during sample processing. As the disulfide form (GSSG) is present only in minimal amounts with respect to the reduced form, a small GSH autoxidation during sample processing can give erroneously high GSSG level. The chapter describes high-performance liquid chromatography (HPLC) method for determining GSSG. It also presents a method for glutathione determ…
Über die autoxydation ungesättigter verbindungen. I. Mitt. Die spontane autoxydation des linolsäuremethylesters
1955
Die Autoxydation des reinen Linolsauremethylesters wird untersucht. Es wird gezeigt, das die Reaktion einen ausgesprochen autokatalytischen Charakter aufweist. Die Kinetik ergibt, das die Autoxydationsgeschwindigkeit proportional mit der Konzentration des entstehenden Peroxyds ansteigt. Die Geschwindigkeitsgleichung wird angegeben. Die Bruttoaktivierungsenergie der autokatalysierten Reaktion wird zu 18 kcal/Mol ermittelt. Es wird eine Apparatur zur gasvolumetrischen Verfolgung der Autoxydation beschrieben. The autoxidation of pure methyl linoleate has been investigated and is shown to have the characteristics of an autocatalytical reaction. The kinetics reveal that the rate of autoxidation …
Support effect on the catalytic performance of Au/Co3O4–CeO2 catalysts for CO and CH4 oxidation
2008
Gold-based catalysts supported on Co3O4, on CeO2 and on mixed Co3O4-CeO2 oxides were prepared by co-precipitation. They were tested in the catalytic oxidation of CO and CH4, in separate tests, and their activities were compared with that of the bare oxides. Tests of CH4 oxidation were performed in two consecutive runs in order to evaluate the catalysts stability. The effect of SO2 in the reactant mixture was investigated. The fresh and spent catalysts were analsed by XRD, BET, TPR and XPS techniques. Among the fresh catalysts, Au supported on CeO2 was the most active in CO oxidation whereas Au supported on Co3O4 was the most active for methane total oxidation. Synergy between the two oxides…
Advances in singlet oxygen chemistry
2005
The authors discuss the advances made in both mechanistic and synthetic aspects of singlet oxygen chem. Formation and reactions of singlet oxygen in heterogeneous media (such as zeolites, micelles, vesicles, etc.) are discussed. Cycloaddns. of mol. oxygen to olefins, heteroatom oxidns. via reaction of singlet oxygen with the electron pair at heteroatoms, and photooxygenations of heterocyclic systems by singlet oxygen are also reviewed.
Über die autoxydation ungesättigter verbindungen. IV. Mitt. Die autoxydation des 2.3-dimethylbutadiens (1.3) und des 10.12-octadecadiensäuremethylest…
1955
Die spontane Autoxydation des Dimethylbutadiens, die zu polymeren Peroxyden fuhrt, wird kinetische verfolgt und mit der Autoxydation des konjugierten 10, 12-Octadecadiensauremethylesters verglichen. Beide Reaktionen verlaufen autokatalytisch. Die Reaktionsgeschwindigkeit ist zu Beginn der Wurzel aus dem Autoxydationsgrad (Mol O2/Mol Substrat) proportional. Die gebildeten Peroxyde zerfallen monomolekular in kettenstartende Radikale. Die Brutto-aktivierungsenergieen werden angegeben. Die Einwirkung von Azodiisobuttersaurenitril, Ascaridol, Di-tert.-Butylperoxyd und Cu++ -oktoat auf die Autoxydation des 10,12-Octadecadiensauremethylesters wird untersucht. Es ergibt sich, das auch die Autoxydat…
Versuche zur Öltrocknung an Modellverbindungen. Die gemeinsame Autoxydation von Styrol und substituierten Styrolen
1962
Die gemeinsame Autoxydation von Styrol und p-substituierten Styrolen wird als Copolymerisation aufgefast. Aus der Zusammensetzung der copolymeren Peroxyde wird uber die Copolymerisations-Parameter auf die Reaktivitat der Peroxy-Radikale und Monomeren geschlossen. Die verschiedenen p-substituierten Styrolperoxy-Radikale zeigen eine unterschiedliche Reaktivitat gegenuber Styrol. Diese Methode erlaubt auch die Reaktivitaten ungesattigter Fettsaureester und der entsprechenden Peroxy-Radikale zu erfassen. Studies on Drying Oils with Model Substances. The Combined Autoxydation of Styrene and Substituted Styrenes The combined autoxidation of styrene and p-substituted styrenes is a copolymerization…
ChemInform Abstract: Electroorganic Synthesis of Nitriles via a Halogen-Free Domino Oxidation-Reduction Sequence.
2016
A direct electroorganic sequence yielding nitriles from oximes in undivided cells is reported. Despite the fact that intermediate nitrile oxides might be formed, the method is viable to prepare benzonitriles without substituents ortho to the aldoxime moiety. This constant current method is easy to perform for a broad scope of substrates and employs common electrodes, such as graphite and lead.
Der nachweis der primärreaktion bei der autoxydation des tetralins
1964
Die Autoxydation des Tetralins wurde bei kleinen Umsatzen durch polarographische oder kolorimetrische Bestimmung des Peroxidgehaltes verfolgt und eine Anfangsgeschwindigkeit gefunden, die groser ist, als sie nach dem Peroxidgehalt des Tetralins sein sollte. Diese zusatzliche Reaktionsgeschwindigkeit ist die der Primarreaktion der Autoxydation. Dabei bilden sich aus Tetralin und molekularem Sauerstoff Radikale. Diese Primarreaktion ist nur dann beobachtbar, wenn der Peroxidgehalt des Tetralins etwa 10−5 Mol/l betragt oder kleiner ist. The autoxidation of tetraline was measured to a low degree of conversion by polarographic or colorimetric determination of tetraline hydroperoxide. The extrapo…