scholarly journals Synthesis and Oxidation ofCobalt(II) Pheophytin-α Complex

2011 ◽  
Vol 8 (s1) ◽  
pp. S297-S303 ◽  
Author(s):  
Ezekiel D. Dikio ◽  
David A. Isabirye
Keyword(s):  
Metal Ion ◽  
Oxidation Reaction ◽  
Dilute Hydrochloric Acid ◽  
Outer Sphere ◽  
Central Metal ◽  
First Order ◽  
First Order Kinetics ◽  
Mechanism Of Oxidation ◽  
Absorption Transitions ◽  
Sphere Mechanism

The mechanism of oxidation of natural pheophytin-aincorporated with cobalt as the central metal ion has been investigated. Natural pheophytin-aextracted from spinach was metallated with cobalt(II) to form the complex, cobalt(II) pheophytin-α[Cophe]. The complex was characterized by Ultraviolet and Visible, Fourier Transform Infrared and Electrospray ion Mass Spectroscopy. The synthesis of cobalt(II) pheophytin-awas carried out and the effect of the substitution on the chlorophyll macrocycle was studied by the reaction of hexaaquachromium(III) cation. The presence of cobalt as the central metal ion increases the energies of the chlorophyll main absorption transitions. The oxidation of the cobalt(II) pheophytin-α, [Cophe] by hexaaquachromium(III) cation in dilute hydrochloric acid has been studied and found to follow first-order kinetics. Rate constants for the oxidation reaction at 313, 322.8 and 332.9 K were found to be 5.4×10-5, 1.8×10-4and 5.9×10-4/s respectively. An outer-sphere mechanism has been proposed for the oxidation of cobalt(II) pheophytin-α.

Protonation effects on dynamic flux properties of aqueous metal complexes

2009 ◽  
Vol 74 (10) ◽  
pp. 1543-1557 ◽  
Author(s):  
Herman P. Van Leeuwen ◽  
Raewyn M. Town
Keyword(s):  
Complex Formation ◽  
Metal Ion ◽  
Good Description ◽  
Minor Component ◽  
Outer Sphere ◽  
Metal Species ◽  
Central Metal ◽  
Inner Sphere ◽  
A Minor ◽  
Protonated Ligand

The degree of (de)protonation of aqueous metal species has significant consequences for the kinetics of complex formation/dissociation. All protonated forms of both the ligand and the hydrated central metal ion contribute to the rate of complex formation to an extent weighted by the pertaining outer-sphere stabilities. Likewise, the lifetime of the uncomplexed metal is determined by all the various protonated ligand species. Therefore, the interfacial reaction layer thickness, μ, and the ensuing kinetic flux, Jkin, are more involved than in the conventional case. All inner-sphere complexes contribute to the overall rate of dissociation, as weighted by their respective rate constants for dissociation, kd. The presence of inner-sphere deprotonated H2O, or of outer-sphere protonated ligand, generally has a great impact on kd of the inner-sphere complex. Consequently, the overall flux can be dominated by a species that is a minor component of the bulk speciation. The concepts are shown to provide a good description of experimental stripping chronopotentiometric data for several protonated metal–ligand systems.

scholarly journals KINETICS OF REACTION BETWEEN MALACHITE GREEN AND HYDROXYL ION IN THE PRESENCE OF REDUCING SUGARS

2015 ◽  
Vol 23 (23) ◽  
pp. 61-72
Author(s):  
Dayo Felix Latona ◽  
Adewumi Oluwasogo Dada
Keyword(s):  
Malachite Green ◽  
Activation Parameters ◽  
Cell Compartment ◽  
First Order ◽  
Rate Determining Step ◽  
First Order Kinetics ◽  
Hydroxyl Ion ◽  
Kinetics Of Reaction ◽  
Kinetics Of ◽  
Sphere Mechanism

The reaction was studied via pseudo-first-order kinetics using a UV-1800 Shimadzu spectrophotometer with a thermostated cell compartment and interfaced with a computer. The reaction showed first order with respect to malachite green and sugar and hydroxyl ion concentrations. However, the reaction was independent of ionic strength and showed no dependence on the salt effect, indicating an inner sphere mechanism for the reaction. There was no polymerization of the reaction mixture with acrylonitrile, indicating the absence of radicals in the course of the reaction. Michaelis-Menten plot indicated the presence of a reaction intermediate in the rate-determining step. The activation parameters of the reaction have been calculated and products were elucidated by FTIR spectroscopy. The stoichiometry of the reaction is 1:1. A mechanism consistent with the above facts has been suggested.

Aerobic oxidative N-dealkylation of secondary amines in aqueous solution catalyzed by rhodium porphyrins

2014 ◽  
Vol 18 (10n11) ◽  
pp. 937-943 ◽  
Author(s):  
Lin Yun ◽  
Ling Zhen ◽  
Zikuan Wang ◽  
Xuefeng Fu
Keyword(s):  
Aqueous Solution ◽  
Oxidation Reaction ◽  
Catalyst Deactivation ◽  
Secondary Amines ◽  
First Order ◽  
Rate Determining Step ◽  
First Order Kinetics ◽  
Biochemical Oxidation ◽  
Iminium Ion ◽  
Rhodium Porphyrins

N-dealkylation demonstrates an important biochemical oxidation reaction by cytochrome P450 and other monooxygenases. In this article, catalytic oxidative N-dealkylation of secondary amines was achieved using rhodium(III) tetra (p-sulfonato-phenyl) porphyrin (( TSPP ) Rh III ) in aqueous solution with oxygen as the sole oxidant. Addition of benzaldehyde to trap primary amine product inhibited catalyst deactivation and dramatically increased reaction turnover numbers (TONs). Substrate scope examination suggested the reaction was performed with a preference for bulkier secondary amines. Kinetic study exhibited first-order kinetics with regard of ( TSPP ) Rh III catalyst. Results from the Hammett study gave a ρ value of -1.38, suggesting formation of an iminium ion intermediate in the rate determining step.

scholarly journals Kinetics and Mechanism of Redox Reaction of Neutral Red with Nitrite Ion in Aqueous Acidic Medium

2016 ◽  
Vol 67 ◽  
pp. 50-57
Author(s):  
Ismaila Ibrahim ◽  
Sulaiman Ola Idris ◽  
Ameh David Onu
Keyword(s):  
Redox Reaction ◽  
Outer Sphere ◽  
Neutral Red ◽  
Nitrite Ion ◽  
First Order ◽  
Hydrochloric Acid Medium ◽  
Plausible Mechanism ◽  
Kinetics Of ◽  
Sphere Mechanism ◽  
Aqueous Acidic Medium

The kinetics of redox reaction of neutral red, NR+, with nitrite ion, NO2-, was studied in aqueous hydrochloric acid medium under pseudo-first order conditions at 25 ± 1°C, [H+] = 2.0 × 10-3mol dm-3, I = 0.1 mol dm-3(NaCl) and λmax= 525 nm. The reaction was first order with respect to [NR+], [NO2-] and [H+]. The reaction displayed a negative Bronsted-Debye salt effect. There was no evidence of the formation of an intermediate complex of significant stability and free radicals are probably not present in the reaction. The observations above, coupled with the result of Michaelis-Menten plot suggests an outer sphere mechanism for the reaction. The reaction obeys the rate law: -d [NR+]/dt = (a + b [H+])[NR+][NO2-]. A plausible mechanism has been proposed for the reaction.

scholarly journals Kinetics and mechanism of the reduction of n-(2-hydroxyethyl)ethylenediaminetriacetatoiron(III) complex by thioglycol in bicarbonate buffer medium

2018 ◽  
Vol 6 (1) ◽  
pp. 102 ◽  
Author(s):  
I U. Nkole ◽  
C R. Osunkwo ◽  
A D. Onu ◽  
O D. Onu
Keyword(s):  
Salt Effect ◽  
Reaction Medium ◽  
Outer Sphere ◽  
Reaction Rates ◽  
Kinetics And Mechanism ◽  
Bicarbonate Buffer ◽  
First Order ◽  
Buffer Medium ◽  
Activated Complex ◽  
Sphere Mechanism

The kinetics and mechanism of reduction of N-(2-hydroxyethyl) ethylenediaminetriacetatoiron (III) complex (hereafter [Fe(III)HEDTAOH2]) by thioglycol (hereafter RSH) has been studied spectrophotometrically in a bicarbonate buffer medium. The study was carried out under pseudo-first order conditions of an excess of thioglycol concentration at 28 ± 1℃, I = 0.44 mol dm-3 (KNO3) and λmax = 490 nm. The reaction is first order in [Fe(III)HEDTAOH2] and half order in [RSH] and a stoichiometric mole ratio of [Fe(III)HEDTAOH2]: RSH is 2:1. Reaction rates increased with increase in ionic strength (I) and dielectric constant (D) of the reaction medium of the reaction. The reaction displayed positive primary salt effect, which suggests the composition of activated complex are likely charged reactants ions. Test for possibility of an intermediate complex formation shows negative as Michaelis-Menten plot was linear with very negligible intercept. Based on the findings, outer-sphere mechanism is proposed for the reaction. The experimental rate law obtained is; - = k2 [Fe(III)HEDTAOH2][RSH]½   

scholarly journals Reduction of tris(2,2’-bipyridine)cobalt(III) complex by thiosulphate ion in an aqueous acidic medium

2021 ◽  
Author(s):  
C.R. Osunkwo ◽  
I.U. Nkole
Keyword(s):  
Acidic Medium ◽  
Outer Sphere ◽  
Reaction Rates ◽  
Ion Concentration ◽  
Third Order ◽  
Hydrogen Ion Concentration ◽  
First Order ◽  
First Order Method ◽  
Sphere Mechanism ◽  
Aqueous Acidic Medium

Abstract The reduction of tris(2,2-bipyridine)cobalt(III) complex by thiosulphate ion in an aqueous acidic medium gave a notable outcome. The stoichiometric evaluation indicates that one mole of the reducing agent has been consumed by one mole of the oxidant, and the reaction complies with an overall equation: 2[Co(bpy)3]3+ + 2S2O32− 2[Co(bpy)3]2+ + S4O62− The kinetics study conducted under a pseudo-first-order method shows that the rate of the reaction was acid-reliant and third-order overall; zero-order in the [oxidant], second-order in the [reductant], and first-order in the hydrogen ion concentration. The empirical rate expression complies with the equation:− [Co(bpy)33+] = a [H+][S2O32−]2‘a’ = 77.82 dm6 mol−2 s−1; at [H+] = 2.0 × 10−2 mol dm−3, µ = 0.4 mol dm−3 (NaCl), T = 28 ± 1˚C and λmax = 560 nm.With increased ionic strength and decreased medium dielectric constant, the reaction rate increased. The inclusion of cations and anions accelerate and constricted the reaction rates respectively. Spectroscopic examination and kinetic evidence indicate an outer sphere mechanism, and the mechanism was therefore proposed via an outer-sphere route.

Kinetics and mechanism of oxidation of V(II) ions with trichloroacetic acid

1980 ◽  
Vol 45 (12) ◽  
pp. 3287-3292 ◽  
Author(s):  
Ľubica Adamčíková
Keyword(s):  
Exchange Rate ◽  
Redox Reaction ◽  
Trichloroacetic Acid ◽  
Outer Sphere ◽  
Kinetics And Mechanism ◽  
Kinetic Measurements ◽  
Exchange Rate Constant ◽  
Marcus Equation ◽  
Mechanism Of Oxidation ◽  
Sphere Mechanism

The kinetics and mechanism of the redox reaction of V(II) ions with trichloroacetic acid were studied in the medium of 0.04-2.0M-HClO. The results of kinetic measurements were compared with the analogous oxidation of U(III) ions with trichloroacetic acid, and the exchange rate constant for the reaction U3+ + *U4+ → U4+ + *U3+ was calculated. The influence of binary mixtures on the kinetic parameters of the reaction and the application of the Marcus' equation show that the oxidation of V2+ions with trichloroacetic acid proceeds by an outer-sphere mechanism.

scholarly journals Kinetics and mechanism of oxidation of mandelic acid with Bi(V) in phosphoric acid medium

2020 ◽  
Vol 16 (5) ◽  
pp. 50-57
Author(s):  
MUKESH KUMAR JHA ◽  
◽  
AVINASH KUMAR ◽  
Keyword(s):  
Electron Transfer ◽  
Phosphoric Acid ◽  
Acid Medium ◽  
Mandelic Acid ◽  
Reaction Rate ◽  
Outer Sphere ◽  
Kinetics And Mechanism ◽  
Opposite Charge ◽  
Mechanism Of Oxidation ◽  
Sphere Mechanism

The kinetics and mechanism of oxidation of Mandelic acid with Bi(V) has been investigated in phosphoric acid medium. The order with respect to substrate and oxidant each is one. The reaction rate is independent of [H+] ion as well as [Bi(III)]. The reaction rate decreases with increasing ionic strength indicating reactive species of opposite charge. The simple rate law explained all the experimental observations. The mode of electron transfer from the substrate to Bi(V) has been indicated is a bridged outer sphere mechanism.

scholarly journals Kinetics and Mechanism of Oxidation of Tartaric Acid by N-Chloronicotinamide (NCN)

2015 ◽  
Vol 52 ◽  
pp. 120-125 ◽  
Author(s):  
L. Pushpalatha
Keyword(s):  
Acetic Acid ◽  
Tartaric Acid ◽  
Fractional Order ◽  
Rate Constants ◽  
Activation Parameters ◽  
First Order ◽  
First Order Kinetics ◽  
Different Temperatures ◽  
Mechanism Of Oxidation ◽  
Experimental Findings

The oxidation of tartaric acid by N-chloronicotinamide in the presence of HClO4 is studied. First order kinetics with respect to NCN is observed. The kinetics results indicate fractional order dependence about [tartaric acid]. Inverse first order in [nicotinamide] and inverse fractional order about [H+] are noted. Rate of the reaction increases with a decrease in the percentage of acetic acid. The values of rate constants observed at four different temperatures were utilized to calculate the activation parameters. A suitable mechanism consistent with the experimental findings has been proposed.

Photo-catalytic degradation of gaseous pollutants in paper mills of southern China

TAPPI Journal ◽  
2018 ◽  
Vol 17 (03) ◽  
pp. 167-178 ◽  
Author(s):  
Xin Tong ◽  
Jiao Li ◽  
Jun Ma ◽  
Xiaoquan Chen ◽  
Wenhao Shen
Keyword(s):  
Degradation Rate ◽  
Southern China ◽  
Catalytic Degradation ◽  
Pulp And Paper ◽  
Gaseous Pollutants ◽  
Pulp And Paper Mills ◽  
Paper Mills ◽  
Initial Concentration ◽  
First Order ◽  
First Order Kinetics

Studies were undertaken to evaluate gaseous pollutants in workplace air within pulp and paper mills and to consider the effectiveness of photo-catalytic treatment of this air. Ambient air at 30 sampling sites in five pulp and paper mills of southern China were sampled and analyzed. The results revealed that formaldehyde and various benzene-based molecules were the main gaseous pollutants at these five mills. A photo-catalytic reactor system with titanium dioxide (TiO2) was developed and evaluated for degradation of formaldehyde, benzene and their mixtures. The experimental results demonstrated that both formaldehyde and benzene in their pure forms could be completely photo-catalytic degraded, though the degradation of benzene was much more difficult than that for formaldehyde. Study of the photo-catalytic degradation kinetics revealed that the degradation rate of formaldehyde increased with initial concentration fitting a first-order kinetics reaction. In contrast, the degradation rate of benzene had no relationship with initial concentration and degradation did not conform to first-order kinetics. The photo-catalytic degradation of formaldehyde-benzene mixtures indicated that formaldehyde behaved differently than when treated in its pure form. The degradation time was two times longer and the kinetics did not reflect a first-order reaction. The degradation of benzene was similar in both pure form and when mixed with formaldehyde.

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