Kinetics and mechanism of oxidation of nickel(II) tetraazamacrocycles by the peroxydisulphate anion in aqueous and binary aqueous mixtures

1992 ◽  
Vol 70 (11) ◽  
pp. 2785-2791 ◽  
Author(s):  
Robert I. Haines ◽  
Sandra J. Northcott
Keyword(s):  
Rate Constants ◽  
Metal Ion ◽  
Ion Pairing ◽  
Ion Pair ◽  
Aqueous Mixtures ◽  
Kinetics Of Oxidation ◽  
Steric Factors ◽  
Temperature Dependences ◽  
Mechanism Of Oxidation ◽  
Kinetics Of

The kinetics of oxidation of several nickel(II) tetraazamacrocycles by the peroxydisulphate anion have been studied in water and in binary aqueous mixtures. The reactions proceed via an ion-pairing pre-equilibrium, followed by metal ion-assisted peroxy-bond fissure within the ion-pair solvent shell. The derived rate law is[Formula: see text]Ion-pairing constants have been determined and have been found to be little influenced by steric factors, but do depend on solvent composition. Rate constants have been extracted using the rate expression and activation energies have been estimated from temperature dependences.

Kinetics of the Oxidation of L-Cysteine by trans- and cis-Cobalt(III) and Iron(III) Complexes

2006 ◽  
Vol 61 (11) ◽  
pp. 1346-1350 ◽  
Author(s):  
Hamzeh M. Abdel-Halim ◽  
Adnan S. Abu-Surrah ◽  
Hutaf M. Baker
Keyword(s):  
Transition Metal ◽  
Rate Constants ◽  
Metal Ion ◽  
Oxidation Process ◽  
Geometrical Isomers ◽  
Kinetics Of Oxidation ◽  
The Difference ◽  
Kinetics Of ◽  
Solution Kinetics ◽  
Cis Isomer

Kinetics of oxidation of L-cysteine by pairs of trans and racemic cis isomers of cobalt(III) and iron(III) based transition metal complexes have been studied in aqueous solution. Kinetics measurements were run under pseudo first order conditions in which the concentration of cysteine is between one and two orders of magnitude greater than that of the isomers of the transition metal complex. The orders of the reaction with respect to both cysteine and the isomer were determined. The observed rate constants and the overall rate constants of the oxidation process were measured. For all geometrical isomers, it was found that the rate constant of oxidation of L-cysteine by the trans isomer is between one to three orders of magnitude greater than that by the cis isomer. The difference in rates can be explained by a geometric factor around the metal ion center in the complex. The less crowded isomer (trans) makes electron transfer easier and hence facilitates the oxidation process which leads to a higher oxidation rate.

Kinetics and mechanism of the reaction of iron(III) with 6-methyl-2,4-heptanedione and 3,5-heptanedione

1990 ◽  
Vol 55 (8) ◽  
pp. 1984-1990 ◽  
Author(s):  
José M. Hernando ◽  
Olimpio Montero ◽  
Carlos Blanco
Keyword(s):  
Aqueous Solution ◽  
Metal Ion ◽  
Activation Parameters ◽  
Enol Form ◽  
Kinetics And Mechanism ◽  
Kinetic Constants ◽  
Steric Factors ◽  
Kinetics Of ◽  
Mechanism Of The Reaction

The kinetics of the reactions of iron(III) with 6-methyl-2,4-heptanedione and 3,5-heptanedione to form the corresponding monocomplexes have been studied spectrophotometrically in the range 5 °C to 16 °C at I 25 mol l-1 in aqueous solution. In the proposed mechanism for the two complexes, the enol form reacts with the metal ion by parallel acid-independent and inverse-acid paths. The kinetic constants for both pathways have been calculated at five temperatures. Activation parameters have also been calculated. The results are consistent with an associative activation for Fe(H2O)63+ and dissociative activation for Fe(H2O)5(OH)2+. The differences in the results for the complexes of heptanediones studied are interpreted in terms of steric factors.

Kinetics of Ion-Pair Effect of Aquation of Bromopentaammine Cobalt(III) Complex in Different Dicarboxylate Media

2011 ◽  
Vol 324 ◽  
pp. 166-169 ◽  
Author(s):  
Farah Zeitouni ◽  
Gehan El-Subruiti ◽  
Ghassan Younes ◽  
Mohammad Amira
Keyword(s):  
Free Energy ◽  
Solvent Effect ◽  
Compensation Effect ◽  
Ion Pairing ◽  
Reaction Rates ◽  
Ion Pair ◽  
Free Energy Of Activation ◽  
Different Types ◽  
Different Temperatures ◽  
Kinetics Of

The rate of aquation of bromopentaammine cobalt(III) ion in the presence of different types of dicarboxylate solutions containing tert-butanol (40% V/V) have been measured spectrophotometrically at different temperatures (30-600°C) in the light of the effects of ion-pairing on reaction rates and mechanism. The thermodynamic and extrathermodynamic parameters of activation have been calculated and discussed in terms of solvent effect on the ion-pair aquation reaction. The free energy of activation ∆Gip* is more or less linearly varied among the studied dicarboxylate ion-pairing ligands indicating the presence of compensation effect between ∆Hip* and ∆Sip*. Comparing the kip values with respect of different buffers at 40% of ter-butanol is introduced.

scholarly journals KINETICS OF OZONE REACTIONS WITH ADENINE AND CYTOSINE IN AQUEOUS SOLUTIONS

2020 ◽  
Vol 63 (10) ◽  
pp. 17-22
Author(s):  
Aigul A. Maksyutova ◽  
Elvina R. Khaynasova ◽  
Yuriy S. Zimin
Keyword(s):  
Aqueous Solutions ◽  
Rate Constants ◽  
Correlation Coefficients ◽  
Activation Parameters ◽  
Second Order ◽  
Order Kinetic ◽  
Temperature Dependences ◽  
Ozone Reactivity ◽  
Kinetics Of ◽  
Ozone Reactions

The ultraviolet spectroscopy method has been applied to study the kinetics of the ozone reactions with nitrogenous bases (NB), namely adenine and cytosine in aqueous solutions. At the first research stage, the range of NB working concentrations has been determined. It was found that linear dependences between optical densities and concentrations of nitrogenous bases aqueous solutions are quite reliable, with correlation coefficients r ≥ 0.998, are satisfied up to [NB] = 2.3 ∙ 10–4 mol/l. According to the Bouguer-Lambert-Beer law, adenine and cytosine extinction coefficients in aqueous solutions were determined and subsequently used to calculate their residual concentrations. At the next stage, the kinetics of nitrogenous bases ozonized oxidation was studied with equal initial concentrations of the starting substances ([NB]0 = [О3]0). The results revealed that the kinetic consumption curves of the starting reagents are fairly well linearized (r ≥ 0.996) in the second-order reaction equation coordinates. As found with the bubbling installation, 1 mol of the absorbed ozone falls on 1 mol of the used NB. Thus, the reactions of ozone with adenine and cytosine explicitly proceed according to the second-order kinetic laws (the first – according to О3 and the first – according to NB). The rate constants were calculated by the integral reaction equations, the values of which indicate a higher ozone reactivity in relation to nitrogen bases. The temperature dependences of the second-order rate constants was studied ranging 285-309 K, and the activation parameters (pre-exponential factors and activation energies) of the ozone reactions with adenine and cytosine in aqueous solutions were determined.

Influence of Aqueous Mixtures of Amides on the Kinetics of Electro Reduction of Ni(II) and Co(II) at d. m. e.

1975 ◽  
Vol 30 (11-12) ◽  
pp. 859-861 ◽  
Author(s):  
S. K. Jha ◽  
S. Jha ◽  
S. N. and
Keyword(s):  
Rate Constants ◽  
Electrode Potential ◽  
Gradual Decrease ◽  
Electrode Kinetics ◽  
Aqueous Mixtures ◽  
Aqueous Mixture ◽  
Kinetics Of ◽  
Remarkable Agreement ◽  
Amide Content

Electroreduction of Ni(II) and Co(II) has been carried out in aqueous mixtures of formamide, acetamide and urea. Electrode kinetics in terms of theories of irreversible waves have been studied. After calculating the rate constants by DELAHAY1 and Kou-TECKY2 treatments separately their variation with electrode potential has been used to calculate the product ‘ana’. The rate constants and ‘ana’ calculated from two different approaches show remarkable agreement. `ana’ records a gradual decrease with increasing amide content of the aqueous mixture.

KINETICS OF THE OXIDATION OF URANIUM (IV) BY IRON (III) IN AQUEOUS SOLUTIONS OF PERCHLORIC ACID

1955 ◽  
Vol 33 (12) ◽  
pp. 1780-1791 ◽  
Author(s):  
R. H. Betts
Keyword(s):  
Electron Transfer ◽  
Ionic Strength ◽  
Aqueous Solutions ◽  
Perchloric Acid ◽  
Rate Constants ◽  
Kcal Mole ◽  
Kinetics Of Oxidation ◽  
Temperature Coefficients ◽  
Kinetics Of ◽  
Rate Controlling Step

The kinetics of oxidation of uranium (IV) by iron (III) in aqueous solutions of perchloric acid have been investigated at four temperatures between 3.1 °C. and 24.8 °C. The reaction was followed by measurement of the amount of ferrous ion formed. For the conditions (H+) = 0.1–1.0 M, ionic strength = 1.02, (FeIII) = 10−4–10−5 M, and (UIV) = 10−4–10−5 M, the observed rate law is d(Fe2+)/dt = −2d(UIV)/dt[Formula: see text]K1 and K2 are the first hydrolysis constants for Fe3+ and U4+, respectively, and K′ and K″ are pseudo rate constants. At 24.8 °C., K′ = 2.98 sec.−1, and K″ = 10.6 mole liter−1 sec−1. The corresponding temperature coefficients are ΔH′ = 22.5 kcal./mole and ΔH″ = 24.2 kcal./mole. The kinetics of the process are consistent with a mechanism which involves, as a rate-controlling step, electron transfer between hydrolyzed ions.

Kinetics of oxidation of reduced cytochrome c by aquacopper(II) and chlorocopper(II) complexes in the presence of oxygen

1981 ◽  
Vol 34 (1) ◽  
pp. 99 ◽  
Author(s):  
JK Yandell
Keyword(s):  
Reaction Mechanism ◽  
Ionic Strength ◽  
Cytochrome C ◽  
Rate Constants ◽  
Kinetics Of Oxidation ◽  
Ferrocytochrome C ◽  
Kinetics Of

The rate constants for the oxidation of reduced cytochrome c by aquacopper(II) ion, aquachloro- copper(II) ion and aquadichlorocopper(II) were found to be 5.7�0.3 1. mol-1 s-1, 2.3×102 1. mol-1 s-1 and 5.6xl031. mol-1 s-1 respectively at 25�C, ionic strength 0.1 and pH 4.0. At low ratios of aquacopper(II) ion to ferrocytochrome c, when oxygen is required to completely oxidize the cytochrome, the reaction mechanism was found to be complex. No evidence for the involvement of copper bound to the cytochrome was found.

Kinetics and mechanism of oxidation of iodide ion by the molybdenum (VI) – hydrogen peroxide system

1990 ◽  
Vol 68 (9) ◽  
pp. 1499-1503 ◽  
Author(s):  
Conchita Arias ◽  
Fernando Mata ◽  
Joaquin F. Perez-Benito
Keyword(s):  
Hydrogen Peroxide ◽  
Rate Constants ◽  
Reaction Rate ◽  
Sodium Molybdate ◽  
Initial Reaction Rate ◽  
Initial Reaction ◽  
Kinetics Of Oxidation ◽  
Iodide Ion ◽  
Aqueous Perchloric Acid ◽  
Kinetics Of

The kinetics of oxidation of potassium iodide by hydrogen peroxide in aqueous perchloric acid has been studied both in the absence and in the presence of sodium molybdate by means of the initial-rates method. The law found for the total initial reaction rate is[Formula: see text]The activation energies associated with rate constants k1, k2, and k3 are 52 ± 1, 49 ± 1, and 42 ± 3 kJ mol−1, respectively. A mechanism in agreement with the experimental kinetic data is proposed, according to which rate constants k1, k2, and k3 correspond to the oxidations of iodide ion by H2O2, H3O2+ and H2MoO5, respectively. Keywords: catalysis, hydrogen peroxide, iodide ion, kinetics, molybdate ion.

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