A Kinetic Study of the Cytochrome c-Hydrogen Peroxide Reaction

2006 ◽  
Vol 71 (11-12) ◽  
pp. 1588-1610 ◽  
Author(s):  
Joaquin F. Perez-Benito
Keyword(s):  
Hydrogen Peroxide ◽  
Oxidative Degradation ◽  
Activation Parameters ◽  
Base Catalysis ◽  
Appreciable Effect ◽  
Prosthetic Group ◽  
Reduction Of Iron ◽  
Initial Reduction ◽  
Heme Prosthetic Group ◽  
Kinetics Of

The kinetics of the reaction of cytochrome c with H2O2 was studied in aqueous phosphate media near physiological pH (5.7-7.2). The UV-VIS spectra indicated that the heme prosthetic group of the protein suffered an oxidative degradation during the reaction. The experimental rate law was v = kexp [cytochrome c] [H2O2], with kexp = (A + B [H+])/(1 + C [H+]). The apparent activation parameters associated with kexp were Ea = 46 ± 2 kJ mol-1, ∆Ho≠ = 43 ± 2 kJ mol-1 and ∆So≠ = -111 ± 5 J K-1 mol-1. The reaction showed base catalysis and was also catalyzed by both CrO42- and acrylamide. It was inhibited by the oxidants WO42-, MoO42-, VO3- and [Fe(CN)6]3- as well as by the reductants [Fe(CN)6]4- and D-mannitol, whereas Zn2+ and superoxide dismutase had no appreciable effect. The results are consistent with initial reduction of iron from Fe(III) to Fe(II) (supported by inhibition caused by most oxidants), followed by a hydroxyl-radical mediated oxidative degradation of the heme prosthetic group (supported by the inhibition caused by both [Fe(CN)6]4- and D-mannitol).

Kinetics and Activation Parameters for the Alkaline Aqueous Rearrangement of Trichorfon [O,O-Dimethyl-(2,2,2-Trichloro-1-Hydroxyethyl) Phosphonate] to Dichlorvos [O,O-Dimethyl-O-(2,2-Dichloroethenyl)Phosphate]

2001 ◽  
Vol 36 (3) ◽  
pp. 589-604 ◽  
Author(s):  
Julian M. Dust ◽  
Christopher S. Warren
Keyword(s):  
Activation Energy ◽  
High Pressure ◽  
Activation Parameters ◽  
Base Catalysis ◽  
Rearrangement Product ◽  
Exponential Factor ◽  
First Order ◽  
Pseudo First Order ◽  
Order Plot ◽  
Kinetics Of

Abstract The kinetics of the alkaline rearrangement of O,O-dimethyl-(2,2,2-trichloro-1- hydroxyethyl)phosphonate, (trichlorfon, 1), the active insecticidal component in such formulations as Dylox, was followed at 25±0.5°C by high pressure liquid chromatography (UV-vis detector, 210 nm). The rearrangement product, O,Odimethyl- O-(2,2-dichloroethenyl)phosphate (dichlorovos, 2), which is a more potent biocide than trichlorfon, undergoes further reaction, and the kinetics, consequently, cannot be treated by a standard pseudo-first-order plot. A two-point van't Hoff (initial rates) method was used to obtain pseudo-first-order rate constants (kѱ) at 25, 35 and 45°C: 2.6 × 10-6, 7.4 × 10-6 and 2.5 × 10-5 s-1, respectively. Arrhenius treatment of this data gave an activation energy (Ea) of 88 kJ·mol-1 with a pre-exponential factor (A) of 5.5 × 109 s-1. Kinetic trials at pH 8.0 using phosphate and tris buffer systems show no buffer catalysis in this reaction and indicate that the rearrangement is subject to specific base catalysis. Estimates are reported for pseudo-first-order half-lives for trichlorfon at pH 8.0 for environmental conditions in aqueous systems in the Corner Brook region of western Newfoundland, part of the site of a recent trichlorfon aerial spray program.

Kinetics of metribuzin degradation by colloidal manganese dioxide in absence and presence of surfactants

2014 ◽  
Vol 68 (1) ◽  
Author(s):  
Qamruzzaman ◽  
Abu Nasar
Keyword(s):  
Sodium Dodecyl ◽  
Oxidative Degradation ◽  
Activation Parameters ◽  
Water Soluble ◽  
Ionic Surfactant ◽  
Ammonium Bromide ◽  
Pseudo First Order Reaction ◽  
First Order ◽  
Colloidal Mno2 ◽  
Kinetics Of

AbstractThe kinetics of the degradation of metribuzin by water-soluble colloidal MnO2 in acidic medium (HClO4) were studied spectrophotometrically in the absence and presence of surfactants. The experiments were performed under pseudo-first-order reaction conditions in respect of MnO2. The degradation was observed to be of the first order in respect of MnO2 while of fractional order for both metribuzin and HClO4. The rate constant for the degradation of metribuzin was observed to decrease as the concentration of MnO2 increased. The anionic surfactant, sodium dodecyl sulphate (SDS), was observed to be ineffective whereas the non-ionic surfactant, Triton X-100 (TX-100), accelerated the reaction rate. However, the cationic surfactant, cetyltrimethyl ammonium bromide (CTAB), caused flocculation with oppositely-charged colloidal MnO2; hence further study was not possible. The catalytic effect of TX-100 was discussed in the light of the available mathematical model. The kinetic data were exploited to generate the various activation parameters for the oxidative degradation of metribuzin by colloidal MnO2 in the absence as well as the presence of the non-ionic surfactant, TX-100.

Kinetics of the Oxidative Degradation of KU-2×8 Cation-Exchange Resin Using Hydrogen Peroxide

2020 ◽  
Vol 94 (12) ◽  
pp. 2450-2458
Author(s):  
M. M. Kozlova ◽  
V. F. Markov ◽  
L. N. Maskaeva ◽  
M. I. Smol’nikov ◽  
S. D. Savinykh
Keyword(s):  
Hydrogen Peroxide ◽  
Cation Exchange ◽  
Exchange Resin ◽  
Cation Exchange Resin ◽  
Oxidative Degradation ◽  
Kinetics Of

Spinel ferrites as catalysts: A study on catalytic effect of coprecipitated ferrites on hydrogen peroxide decomposition

1991 ◽  
Vol 69 (1) ◽  
pp. 33-36 ◽  
Author(s):  
Preeti Lahiri ◽  
Susanta K. Sengupta
Keyword(s):  
Hydrogen Peroxide ◽  
Compensation Effect ◽  
Activation Parameters ◽  
Neutral Medium ◽  
Specific Rate ◽  
Hydrogen Peroxide Decomposition ◽  
Peroxide Decomposition ◽  
Co Precipitation ◽  
Kinetics Of ◽  
Catalytic Power

Some ferrospinels act as catalysts for the decomposition of H2O2, their effectiveness is dependent on the composition of the catalyst. This study is to find the most effective catalyst of stoichiometry MIIFe2IIIO4. A set of ferrites of different composition MIIFe2II04 (MII = Mn, Co, Ni, Cu, Zn, Cd) was synthesized by co-precipitation and characterized by chemical analysis, X-ray diffractometry, and B.E.T. technique. A comparative assessment of the catalytic power of these ferrites from investigations of their influence on the kinetics of H2O2 decomposition in a neutral medium was made. An analysis of the data on specific rate, and the Eyrings activation parameters for the reaction sharply reveal the following: (a) The catalytic power follows the order MnFe2O4 > CoFe2O4 > CuFe2O4 > NiFe2O4 > CdFe2O4 > ZnFe2O4, MnFe2O4 is much more highly effective than the others (50–100 fold). (b) A compensation effect has been noted from the observed linearity with slightly less than unity slope between TΔ≠S0 and Δ≠H0 over the entire series. Key words: Ferrospinels, catalysis, hydrogen peroxide decomposition kinetics.

scholarly journals Kinetics of Micellar Effect of Non-Ionic Surfactant on Oxidative Degradation of Ciprofloxacin

2019 ◽  
Vol 32 (2) ◽  
pp. 359-368
Author(s):  
Ajaya Kumar Singh ◽  
Alpa Shrivastava ◽  
Dilip R. Shrivastava ◽  
Rajmani Patel ◽  
Neerja Sachdev
Keyword(s):  
Degradation Kinetics ◽  
Oxidative Degradation ◽  
Activation Parameters ◽  
Solvent Polarity ◽  
Degradation Process ◽  
Oxidation Products ◽  
Ionic Surfactant ◽  
Reaction Conditions ◽  
Chloramine T ◽  
Kinetics Of

Oxidative degradation kinetics of leading fluoroquinolone family drug ciprofloxacin (CIP) by chloramine-T (CAT) in TX-100 micelle media was studied spectrophotometrically at 275 nm and 298 K. In pseudo-first-order conditions the rate constant (kobs) decreased regularly with increasing [TX-100]. To understand the self-organizing activities of TX-100, CMC values in varying reaction conditions had been evaluated. The role of non-ionic surfactant in the oxidative degradation process of ciprofloxacin by chlorinating agent chloramine-T is explained in terms of mathematical model explained by Menger-Portnoy. The reaction showed first to zero order dependence on [CAT] and fractional order on [CIP]. Increasing [H+] decreased the rate of reaction. The effect of ionic strength and solvent polarity of the medium in reaction conditions were studied. The effects of added salts [HSO4Na], [KCl], [KNO3] and [K2SO4] had also been studied. The stoichiometry of the reaction determined was 1:2 and the oxidation products were identified by LC-EI-MS. The analysis of degradation product of ciprofloxacin evidently reveals that the piperazine moiety is active site for oxidation in the reaction. Activation parameters were studied to propose appropriate mechanism for the reaction.

Kinetics of oxidation of the bis(ethylenediamine)mercaptoacetatocobalt(III) and cysteinato-bis(ethylenediamine)cobalt(III) ions by hydrogen peroxide in mixed aqueous-nonaqueous solutions

1988 ◽  
Vol 53 (3) ◽  
pp. 554-562
Author(s):  
Ján Benko ◽  
Oľga Vollárová ◽  
Miroslav Kovarčík
Keyword(s):  
Hydrogen Peroxide ◽  
Reaction Rate ◽  
Activation Parameters ◽  
Butyl Alcohol ◽  
Acid Base ◽  
Kinetics Of Oxidation ◽  
Tert Butyl Alcohol ◽  
Alcohol Water ◽  
Acid Base Equilibrium ◽  
Kinetics Of

The kinetics of oxidation of the coordinatively bonded sulphur in the cysteinato-bis(ethylenediamine)cobalt(III) and bis(ethylenediamine)mercaptoacetatocobalt(III) complexes by hydrogen peroxide to the sulphoxides was examined in HClO4 solutions (c(HClO4) = 1 – 500 mmol l-1) with a view to obtaining data characterizing the effect of the acid-base equilibria of the reactants on the reaction rate. The reaction rate was found affected particularly by the acid-base equilibrium of the oxidant, which plays a role in strongly acid solutions. The oxidation was also studied in water-methyl alcohol, water-tert-butyl alcohol and water-ethylene glycol mixtures, and the effect of the mole fraction of the nonaqueous component on the rate constant and thermodynamic activation parameters was examined.

The oxidation of hydrogen peroxide by tris(polypyridine) complexes of osmium(III), iron(III), ruthenium(III), and nickel(III) in aqueous media

1986 ◽  
Vol 64 (9) ◽  
pp. 1936-1942 ◽  
Author(s):  
Donal H. Macartney
Keyword(s):  
Hydrogen Peroxide ◽  
Exchange Rate ◽  
Rate Constant ◽  
Aqueous Media ◽  
Activation Parameters ◽  
Exchange Rate Constant ◽  
Oxidation Of Hydrogen ◽  
Polypyridine Complexes ◽  
Ph Range ◽  
Kinetics Of

The stoichiometry and kinetics of the oxidation of hydrogen peroxide by tris(2,2′-bipyridine) and tris(4,4′-dimethyl-2,2′-bipyridine) complexes of osmium(III), iron(III), ruthenium(III), and nickel (III) were studied in acidic and neutral aqueous media at 25 °C and I = 0.50 M (LiCF3SO3). The reaction 2M(bpy)33+ + H2O2 → 2M(bpy)32+ + O2 + 2H+ is observed with quantitative yields of dioxygen gas. The observed rate constants displayed an inverse acid dependence over the pH range 6.0–8.5; kobsd = k1 + k2K1/[H+], attributed to the oxidations of H2O2(k1) and HO2− (k2). An application of the Marcus theory relationship to the cross-reaction data gave a self-exchange rate constant of 10−2–10−1 M−1 s−1 for the HO2−/HO2 couple. The electron exchange rate constant is evaluated in terms of the inner-sphere and solvent reorganizational barriers and is compared to values reported for other small molecule couples. Rate and activation parameters for the reduction of the nickel(III) complexes by the hydroxide ion have been determined and are compared with the corresponding values for other metal tris(poly pyridine) complexes.

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