ChemInform Abstract: Synthesis of Perhydrocyclopenta(c)pyrroles by a Tandem Rearrangement- Autoxidation Reaction.

ChemInform ◽  
2010 ◽  
Vol 26 (22) ◽  
pp. no-no
Author(s):  
J.-L. MALLERON ◽  
J.-F. PEYRONEL ◽  
P. DESMAZEAU ◽  
C. M'HOUMADI ◽  
C. PLANIOL
Keyword(s):  
Autoxidation Reaction

A Computational Fluid Dynamics and Chemistry Model for Jet Fuel Thermal Stability

1992 ◽  
Vol 114 (1) ◽  
pp. 104-110 ◽  
Author(s):  
J. L. Krazinski ◽  
S. P. Vanka ◽  
J. A. Pearce ◽  
W. M. Roquemore
Keyword(s):  
Fluid Dynamics ◽  
Activation Energy ◽  
Computational Fluid Dynamics ◽  
Dissolved Oxygen ◽  
Deposition Process ◽  
Decomposition Reaction ◽  
Heated Tube ◽  
Precursor Decomposition ◽  
Autoxidation Reaction ◽  
Decomposition Chemistry

This paper describes the development of a model for predicting the thermal decomposition rates of aviation fuels. A thermal deposition model was incorporated into FLANELS-2D, an existing computational fluid dynamics (CFD) code that solves the Reynolds-averaged conservation equations of mass, momentum, and energy. The decomposition chemistry is modeled by three global Arrhenius expressions in which the fuel decomposition was assumed to be due to an autoxidation reaction with dissolved oxygen. The deposition process was modeled by assuming that all deposit-forming species transported to the wall adhered and formed a deposit. Calibration of the model required the determination of the following parameters for a given fuel: (1) the pre-exponential constant and activation energy for the wall reaction, (2) the pre-exponential constant and activation energy for the bulk autoxidation reaction, and (3) the pre-exponential constant and activation energy for the precursor decomposition reaction. Values for these parameters were estimated using experimental data from published heated-tube experiments. Results show that the FLANELS-2D code performed well in estimating the fuel temperatures and that the three-equation chemistry model performed reasonably well in accounting for both the rate of deposition and the amount of dissolved oxygen present in the fuel at the end of the heated tube.

Über die Bildung von Wasserstoffperoxyd bei der Hemmung der Glykolyse von Ascites-Tumorzellen durch Phenanthrenchinon

1961 ◽  
Vol 16 (2) ◽  
pp. 120-126 ◽  
Author(s):  
Heinz Tiedemann ◽  
Hans-Jörg Risse
Keyword(s):  
Tumor Cell ◽  
Cell Suspension ◽  
Tumor Cells ◽  
Respiratory Chain ◽  
Kidney Cell ◽  
Ehrlich Ascites Tumor Cells ◽  
Ascites Tumor ◽  
Ehrlich Ascites ◽  
Autoxidation Reaction ◽  
Stimulation Of

Under aerobic conditions hydrogenperoxide is formed in a glycolyzing suspension of Ehrlich-Ascites tumor cells after incubation with phenanthraquinone(9.10). Not glycolyzing tumor cells and also a kidney cell suspension produce very little hydrogenperoxide only.In glycolyzing tumor cells phenanthraquinone(9.10) is reduced rapidly to the corresponding hydroquinone. During the autoxidation of the hydroquinone hydrogenperoxide is formed. A great stimulation of O2-uptake is related with the autoxidation reaction. This stimulation also appears after blocking the respiratory chain by cyanide.The inhibition of tumor cell glycolysis is caused by an inhibition of glycerinaldehydphosphatdehydrogenase and a decrease of the DPN level.

Electron transfer and autoxidation kinetics of the bis(imidazole)bis(dimethylglyoximato)iron(II) complex

1986 ◽  
Vol 64 (7) ◽  
pp. 1230-1235 ◽  
Author(s):  
Henrique E. Toma ◽  
Antonio Carlos C. Silva
Keyword(s):  
Aqueous Solution ◽  
Electron Transfer ◽  
Cyclic Voltammetry ◽  
Stopped Flow ◽  
Imidazole Ligand ◽  
Autoxidation Reaction ◽  
Stopped Flow Kinetics ◽  
Kinetics Of

The properties and reactivity of the bis(imidazole)bis-(dimethylglyoximato)iron(II) complex have been studied based on spectroelectrochemistry, cyclic voltammetry, and stopped-flow kinetics in aqueous solution. The autoxidation reaction was found to be inhibited by the imidazole ligand in excess but susceptible to copper(II) catalysis. In this case a mechanism has been proposed, consisting of a rapid electron transfer followed by the reoxidation of the resulting Cu(I) species by O2.

scholarly journals Autoxidation of soluble trypsin-cleaved microsomal ferrocytochrome b5 and formation of superoxide radicals

1976 ◽  
Vol 157 (1) ◽  
pp. 237-246 ◽  
Author(s):  
M C Berman ◽  
C M Adnams ◽  
K M Ivanetich ◽  
J E Kench
Keyword(s):  
Superoxide Dismutase ◽  
Rate Constant ◽  
Phosphate Buffer ◽  
Electron Flow ◽  
Cytochrome B5 ◽  
Significant Proportion ◽  
Intrinsic Property ◽  
Order Rate Constant ◽  
Rapid Phase ◽  
Autoxidation Reaction

The rate and mechanism of autoxidation of soluble ferrocytochrome b5, prepared from liver microsomal suspensions, appear to reflect an intrinsic property of membrane-bound cytochrome b5. The first-order rate constant for autoxidation of trypsin-cleaved ferrocytochrome b5, prepared by reduction with dithionite, was 2.00 × 10(−3) +/− 0.19 × 10(−3) S-1 (mean +/− S.E.M., n =8) when measured at 30 degrees C in 10 mM-phosphate buffer, pH 7.4. At 37 degrees C in aerated 10 mM-phosphate buffer (pH 7.4)/0.15 M-KCl, the rate constant was 5.6 × 10(-3) S-1. The autoxidation reaction was faster at lower pH values and at high ionic strengths. Unlike ferromyoglobin, the autoxidation reaction of which is maximal at low O2 concentrations, autoxidation of ferrocytochrome b5 showed a simple O2-dependence with an apparent Km for O2 of 2.28 × 10(-4) M (approx. 20kPa or 150mmHg)9 During autoxidation, 0.25 mol of O2 was consumed per mol of cytochrome oxidized. Cyanide, nucleophilic anions, EDTA and catalase each had little or no effect on autoxidation rates. Adrenaline significantly enhanced autoxidation rates, causing a tenfold increase at 0.6 mM. Ferrocytochrome b5 reduced an excess of cytochrome c in a biphasic manner. An initial rapid phase, independent of O2 concentration, was unaffected by superoxide dismutase. A subsequent slower phase, which continued for up to 60 min, was retarded at low O2 concentrations and inhibited by 65% by superoxide dismutase at a concentration of 3 mug/ml. It is concluded that autoxidation is responsible for a significant proportion of electron flow between cytochrome b5 and O2 in liver endoplasmic membranes, this reaction being capable of generating superoxide anions. A biological role for the reaction is discussed.

scholarly journals Thiol oxidation coupled to DT-diaphorase-catalysed reduction of diaziquone. Reductive and oxidative pathways of diaziquone semiquinone modulated by glutathione and superoxide dismutase

1992 ◽  
Vol 286 (2) ◽  
pp. 481-490 ◽  
Author(s):  
I D Ordoñez ◽  
E Cadenas
Keyword(s):  
Superoxide Dismutase ◽  
H2o2 Production ◽  
Kinetic Properties ◽  
Thiol Oxidation ◽  
Relative Contribution ◽  
Autoxidation Reaction ◽  
Redox Transitions ◽  
Electron Reduction ◽  
Dt Diaphorase ◽  
State Concentration

DT-diaphorase [NAD(P)H:quinone oxidoreductase; EC 1.6.99.2] catalysed the two-electron reduction of the anti-tumour quinone 2,5-bis-(1-aziridinyl)-3,6-bis(ethoxycarbonylamino)-1,4-benzoquino ne (AZQ) to the hydroquinone form (AZQH2). Although DT-diaphorase catalysis of AZQ was not significantly affected by pH, the hydroquinone product was effectively stabilized by protonation at pH values below 7, whereas, above that pH, hyroquinone autoxidation, evaluated in terms of H2O2 production, increased exponentially. The autoxidation of AZQH2 entailed the formation of diverse radicals, such as O2-.,HO., and the semiquinone form of AZQ (AZQ-.), which contributed to different extents to the e.p.r. spectrum. Superoxide dismutase enhanced the autoxidation of AZQH2 and suppressed the e.p.r. signal ascribed to AZQ-., in agreement with a displacement of the equilibrium of the semiquinone autoxidation reaction (AZQ-.+O2 in equilibrium with AZQ+O2-.) upon enzymic withdrawal of O2-.. GSH increased the steady-state concentration of AZQH2 formed during DT-diaphorase catalysis and inhibited temporarily its autoxidation. This effect was accompanied by oxidation of the thiol to the disulphide within a process involving glutathionyl radical (GS.) formation, the relative contribution of which to the e.p.r. spectrum was enhanced by increasing GSH concentrations. GS. formation in this experimental model can be rationalized as originating from the reaction of GSH with AZQ-., rather than with O2-. or HO., for thiol oxidation was not affected significantly by superoxide dismutase, and GS. formation was insensitive to catalase. In addition, GSH suppressed the e.p.r. signal attributed to AZQ-.. No glutathionyl-quinone conjugate was detected during the DT-diaphorase-catalysed reduction of AZQ; although the chemical requirements for alkylation were partly fulfilled (quinone ring aromatization and acid-assisted aziridinyl ring opening), the negligible dissociation of GSH (GS(-)+H+ in equilibrium with GSH) at low pH prevented any nucleophilic addition to occur. Therefore the redox transitions of AZQ during DT-diaphorase catalysis seemed to be centred on the semiquinone species, the fate of which was inversely affected by catalytic amounts of superoxide dismutase and large amounts of GSH: the former enhanced AZQ-. autoxidation and the latter favoured AZQ-. reduction. Accordingly, superoxide dismutase and GSH suppressed the semiquinone e.p.r. signal. These results are discussed in terms of three interdependent redox transitions (comprising one-electron transfer reactions involving the quinone, oxygen and the thiol) and the thermodynamic and kinetic properties of the reactions involved.

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