scholarly journals Kinetics and Mechanism of the Redox Reaction Between Pt(IV) Complex Ions and Sodium Thiosulfate in Aqueous Solution. Part II: Neutral and Alkaline Solution/ Kinetyka I Mechanizm Reakcji Redoks Pomiędzy Jonami Kompleksowymi Pt(Iv) I Tiosiarczanem Sodu W Roztworze Wodnym. Część II: Roztwór Obojętny I Zasadowy

2014 ◽  
Vol 59 (4) ◽  
pp. 1421-1426
Author(s):  
K. Pacławski ◽  
J. Piwowonska
Keyword(s):  
Rate Constant ◽  
Redox Reaction ◽  
Sodium Thiosulfate ◽  
Order Rate Constant ◽  
Reduction Reaction ◽  
Kinetics And Mechanism ◽  
Complex Ions ◽  
Entropy Of Activation ◽  
Enthalpy And Entropy ◽  
Mechanism Of The Reaction

Abstract In this work, spectrophotometric studies on the kinetics and mechanism of the reaction between [PtCl6]2- complex ions and sodium thiosulfate, in neutral (pH = 7) and alkaline (p = 12) solution, were carried out. Applying different conditions, the influence of initial concentrations of reductant and platinum(IV) complex ions as well as the influence of temperature and ionic strength on the rate constant, was experimentally determined. From the obtained results, the molecularity, the order and the value of enthalpy and entropy of activation of the reaction, were experimentally determined. It was found that in both cases the reduction reaction is relatively slow and in the studied conditions the second-order rate constant changes from 2.92 : 10-2 to 0.40 M-1:s-1 at pH = 7, and from 3.84 : 10-2 to 1.55 M-1s-1 at pH = 12. Additionally, depending on the pH, different mechanism of the reaction is present. However, regardless on the studied system the only platinum(II) chloride complex ions are the final product of the redox reaction.

scholarly journals Kinetics and Mechanism of the Redox Reaction Between Pt(IV) Chloride Complex Ions and Sodium Thiosulfate in Aqueous Solution. Part I: Acidic Solution/ Kinetyka I Mechanizm Reakcji Redox Pomiędzy Chlorkowymi Jonami Kompleksowymi Pt(Iv) I Tiosiarczanem Sodu W Roztworach Wodnych. Część I: Roztwór Kwaśny

2014 ◽  
Vol 59 (4) ◽  
pp. 1413-1420 ◽  
Author(s):  
K. Pacławski ◽  
J. Piwowonska
Keyword(s):  
Acidic Solution ◽  
Solid Phase ◽  
Sodium Thiosulfate ◽  
Chloride Complex ◽  
Elementary Step ◽  
Kinetics And Mechanism ◽  
Complex Ions ◽  
Mechanism Of Reaction ◽  
Entropy Of Activation ◽  
Enthalpy And Entropy

Abstract In this work, spectrophotometric studies of the kinetics and mechanism of reaction between [PtCl6]2- complex ions and sodium thiosulfate, were carried out. The influence of different conditions, such as: initial concentrations of reductant and platinum(IV) complex ions, ionic strength, pH and temperature on the rate constant, was experimentally determined. From the obtained results, the molecularity of the first elementary step, value of the enthalpy and entropy of activation in Eyring equation as well as corresponding rate equation, were experimentally determined. It was found that the reaction is relatively slow and leads to the S, Pt and PtS colloids formation. The best conditions for solid phase formation containing Pt are at pH = 5.

Kinetics and mechanism of the reaction of dimethyl acetylphosphonate with water. Expulsion of a phosphonate ester from a carbonyl hydrate

1978 ◽  
Vol 56 (13) ◽  
pp. 1792-1795 ◽  
Author(s):  
Ronald Kluger ◽  
David C. Pire ◽  
Jik Chin
Keyword(s):  
Rate Constant ◽  
Electronic Effect ◽  
Order Rate Constant ◽  
Ion Concentration ◽  
First Order ◽  
Cleavage Reactions ◽  
Ph Range ◽  
Rapid Hydrolysis ◽  
Hydrolysis Of ◽  
Mechanism Of The Reaction

Dimethyl acetylphosphonate (DAP) is rapidly cleaved in water to acetate and dimethylphosphonic acid. The half time for reaction at pH 7, 25 °C is estimated to be 3 s. The reaction is first order in hydroxide ion concentration and first order in DAP concentration. Rates of reaction were measured over the pH range 3.8 to 6.5 at 25 °C, 6.5 and 7.0 at 5 °C, 4.5 to 6.5 at 35 °C, and 4.5 to 6.0 at 45 °C. The average observed second-order rate constant at 25 °C is 2.4 × 106M−1 s−1. DAP is converted rapidly to a hydrated carbonyl adduct. The mechanism for the formation of the observed products is proposed to be analogous to cleavage reactions of other carbonyl hydrates, proceeding from a monoanion conjugate in this case. The estimated rate constant for the unimolecular cleavage of the carbonyl hydrate anion is 2 × 103 s−1. The rapid hydrolysis of DAP results from energetically favourable formation of a hydrate due to the electronic effect of the phosphonate diester. This effect also promoles ionization of the hydrate. The ionized hydrate readily expels the phosphonate diester to achieve the overall rapid hydrolysis.

scholarly journals Simultaneous Studies of Redox Reaction of Chromium(VI) and Arsenic(III) in Aqueous Phase: A Kinetic and Mechanistic Approach

2020 ◽  
pp. 18-29
Author(s):  
Iorhuna, T. Boniface ◽  
Wuana, A. Raymond ◽  
Yiase, G. Stephen
Keyword(s):  
Aqueous Phase ◽  
Rate Constant ◽  
Rate Equation ◽  
Redox Reaction ◽  
Order Rate Constant ◽  
Chromium Vi ◽  
Mechanistic Approach ◽  
Ester Formation ◽  
Plausible Mechanism ◽  
Uv Visible

A kinetic and mechanistic approach was used to simultaneously study the oxidation of As(III) and reduction of Cr(VI) in aqueous phase, and in the presence of Fe(III). Reactions were monitored by UV-visible spectrophotometry. The stoichiometry of the reaction was . The rate equation for the reaction is proposed as  where k2 is the second order rate constant. The reaction was not affected by Fe(III) ions within the studied concentration range of 0.001 – 0.009 molL-1. From the reaction between   a plausible mechanism involving an ester formation by the reactants leading to the eventual formation of As(V) and Cr(III) was proposed.

Electron self-exchange, oxidation, and reduction reactions of bis(2,9-dimethyl-4,7-diphenyl- 1,10-phenanthroline)copper(II/I) and bis(6,6'-dimethyl-2,2'-bipyridine)copper(II/I) couples in acetonitrile: gated ET for the reduction, oxidation, and self-exchange processes

1999 ◽  
Vol 77 (9) ◽  
pp. 1498-1507 ◽  
Author(s):  
Nobuyoshi Koshino ◽  
Yoshio Kuchiyama ◽  
Shigenobu Funahashi ◽  
Hideo D Takagi
Keyword(s):  
Exchange Rate ◽  
Rate Constant ◽  
Order Rate Constant ◽  
Reduction Reaction ◽  
Ligand Field ◽  
Oxidation Reactions ◽  
Reduction Reactions ◽  
Nmr Method ◽  
Exchange Processes ◽  
Exchange Rate Constant

The electron self-exchange rate constant for the Cu(dmbp)22+/+ couple (dmbp = 6,6'-dimethyl-2,2'-bipyridine) was measured in acetonitrile by the NMR method (kex = 5.5 × 103 kg mol-1 s-1, ΔH* = 35.0 ± 0.3 kJ mol-1 and ΔS* = -56 ± 1 J mol-1 K-1). Reduction reactions of Cu(bcp)22+ (bcp = 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) and Cu(dmbp)22+ with Co(bipy)32+ (bipy = 2,2'-bipyridine) and ferrocene (Fe(Cp)2 = bis(cyclopentadienyl)iron(II)), and oxidation reactions of Cu(bcp)2+ and Cu(dmbp)2+ by Ni(tacn)23+ (tacn = 1,4,7-triazacyclononane) and Mn(bipyO2)33+ (bipyO2 = N,N'-dioxo-2,2'-bipyridine) were also studied in acetonitrile. The electron self-exchange rate constants, kex, estimated for the Cu(bcp)22+/+ and Cu(dmbp)22+/+ couples from the oxidation reactions of Cu(bcp)2+ and Cu(dmbp)2+ by Ni(tacn)23+ and Mn(bipyO2)33+ were consistent with the directly measured values by NMR, while kex estimated from the reduction reactions of Cu(bcp)22+ and Cu(dmbp)22+ by Co(bipy)32+ ([Cu(bcp)22+]0, [Cu(dmbp)22+]0 >> [Co(bipy)32+]0) were 103 times smaller than those directly measured by the NMR method. The pseudo-first-order rate constant for the reduction reaction of Cu(bcp)22+ and Cu(dmbp)22+ by Fe(Cp)2 was not linear against the concentration of excess amounts of Fe(Cp)2. Analyses of the reactions revealed that the reductions of Cu(bcp)22+ and Cu(dmbp)22+ involve slow paths related to the deformation of Cu(II)N4 center from tetragonal to tetrahedral coordination. The energetic preference for the deformation of Cu(II) species rather than that of Cu(I) was discussed on the basis of the ligand field activation energy (LFAE).Key words: electron transfer, copper(II) and copper(I) complexes, gated behavior.

Kinetics and Mechanism of the Reaction of Mercury(II) with a Water-soluble Octabromoporphyrin

1998 ◽  
Vol 02 (05) ◽  
pp. 397-403 ◽  
Author(s):  
N. NAHAR ◽  
M. TABATA
Keyword(s):  
Rate Constant ◽  
Activation Parameters ◽  
High Reactivity ◽  
Kinetics And Mechanism ◽  
Water Soluble ◽  
First Order ◽  
Rate Expression ◽  
Ph Range ◽  
Mechanism Of The Reaction

The reaction of mercury(II) hydroxide with 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin, [Formula: see text]( H 2P4−), to form the mercury(II) porphyrin [( TPPSBr 8) Hg ]4−( HgP 4−) was investigated in the pH range 6.2-8.5. The observed rate constant was first-order with respect to the mercury(II) concentration and decreased with increasing pH from pH 6.2 to 7.5 and then increased from pH 7.5 to 8.5. The rate expression was written as d [ HgP 4−]/dt = (kHPK−1[ H +]−1 + k H 2 P + k H 3P K 1[ H +])(1 + K1[ H +] + K−1[ H +]−1)−1[ Hg ( OH )2][ H 2 P 4−]. The kHP, kH2P and kH3P values were found to be (1.33 ± 0.02) × 108, (5.50 ± 0.08) × 106 and (1.40 ± 0.08) × 108 M −1 s−1 respectively, with K1 = [ H 3 P 3−][ H 2 P 4−]−1[ H +]−1 = 104.83 ± 0.04 and K−1 = [ HP 5−][ H +][ H 2 P 4−]−1 = 1010.02 ± 0.02. The activation parameters were [Formula: see text] and ΔS‡ HP = 226 ± 22 J K −1 mol −1 for the k HP path, [Formula: see text] and [Formula: see text] for the k H 2 P path and [Formula: see text] and [Formula: see text] for the k H 3 P path. The kinetic results show the high reactivity of mercury(II) hydroxide towards the protonated porphyrin.

Kinetics and Mechanism of the Cleavage of N-Phthaloylglycine in Buffers of Some Primary Amines

2002 ◽  
Vol 2002 (12) ◽  
pp. 593-595 ◽  
Author(s):  
M. Niyaz Khan ◽  
Norsaadah H. Ismail
Keyword(s):  
Kinetic Parameters ◽  
Rate Constant ◽  
Kinetic Studies ◽  
Order Rate Constant ◽  
Second Order ◽  
Kinetics And Mechanism ◽  
Primary Amines ◽  
Buffer Concentration ◽  
Nucleophilic Cleavage ◽  
The Relationship

Kinetic studies on the nucleophilic cleavage of N-phthaloylglycine (NPG) in buffers of 2-methoxyethylamine, and 2-hydroxyethylamine reveal the relationship: knapp = A1 [Am]T/(1 + A2 [Am]T) where A1 and A2 are constants (kinetic parameters) and knapp and [Am]T represent apparent nucleophilic second-order rate constant and total amine buffer concentration, respectively.

scholarly journals The Mechanism of Redox Reaction between Palladium(II) Complex Ions and Potassium Formate in Acidic Aqueous Solution

2017 ◽  
Vol 62 (2) ◽  
pp. 737-745 ◽  
Author(s):  
M. Wojnicki ◽  
A. Podborska
Keyword(s):  
Redox Reaction ◽  
Arrhenius Equation ◽  
Complex Structure ◽  
Reduction Reaction ◽  
Chloride Ions ◽  
Chloride Complex ◽  
Complex Ions ◽  
Acidic Aqueous Solution ◽  
Process Dynamics ◽  
Kinetics Studies

AbstractThe kinetics studies of redox reaction between palladium(II) chloride complex ions and potassium formate in acidic aqueous solutions was investigated. It was shown, that the reduction reaction of Pd(II) is selective in respect to Pd(II) complex structure. The kinetic of the process was monitored spectrophotometrically. The influence of chloride ions concentration, Pd(II) initial concentration, reductant concentration, ionic strength as well as the temperature were investigated in respect to the process dynamics. Arrhenius equation parameters were determined and are equal to 65.8 kJ/mol, and A = 1.12×1011s−1.

scholarly journals XAFS in the Tracking of Reactions in Aqueous Solution: a Case of Redox Reaction Between [AuCl4]– Complex Ions and Ethanol / Metoda XAFS W Badaniach Reakcji Zachodzących W Roztworach Wodnych: Przykład Reakcji Redoks Pomiędzy Jonami Kompleksowymi [AuCl4]- I Alkoholem Etylowym

2012 ◽  
Vol 57 (4) ◽  
pp. 1011-1020 ◽  
Author(s):  
K. Pacławski ◽  
M. SIKORA
Keyword(s):  
Aqueous Solution ◽  
Rate Constant ◽  
Potential Application ◽  
Kinetic Curve ◽  
Order Rate Constant ◽  
Metallic Phase ◽  
Complex Ions ◽  
Kinetic Measurements ◽  
Kinetics Of ◽  
Continuous Flow Method

In this work the potential application of synchrotron radiation in the studies of reaction kinetics in aqueous phase were presented. After short introduction describing principles of technique and potential application of XAFS for the structural studies of reacting species, the experimental results of kinetic measurements of reaction between gold(III) chloride complex ions and ethanol were presented. Analyzing the changes of absorption intensity in the XANES spectra registered at Au-L3 edge during the reaction, the change of the valence state of Au central atom (form 3+to 0) of reacting complex ion was determined. Moreover, empirical XANES data gave the chance to register the kinetic curve and to determine the rate constant of the studied reaction. It was found that reaction is relatively slow (second-order rate constant k = 3.66 · 10-5 M-1s) and lead to the gold metallic phase formation in the system. Applying the continuous-flow method, within the first 600 ms of reaction the changes in XANES spectra were registered. From the obtained results, supported with numerical calculations, two intermediate forms of adducts appearing prior the electron transfer were suggested. It was concluded that when the classic methods, e.g. UV-Vis spectrophotometry, cannot be applied to studies of kinetics of reactions in aqueous solution, the XAFS technique can be a valuable and substitutive (or supplementary) tool for such measurements.

Kinetics and mechanism of the oxidation of mercury by peroxidase

1985 ◽  
Vol 63 (11) ◽  
pp. 2940-2944 ◽  
Author(s):  
Donald C. Wigfield ◽  
Season Tse
Keyword(s):  
Hydrogen Peroxide ◽  
Electron Transfer ◽  
Horseradish Peroxidase ◽  
Rate Constant ◽  
Order Rate Constant ◽  
Kinetics And Mechanism ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Iron Heme ◽  
Kinetics Of

The kinetics of oxidation of zero-valent mercury by the horseradish peroxidase system are reported. The reaction is first order in mercury and first order in peroxidase compound 1, and appear to obey these kinetics to completion of the reaction. The second order rate constant is 8.58 × 105 M−1 min−1 at 23 °C. The data are consistent with a simple two-electron transfer from mercury to the iron–heme system of peroxidase with the enzyme acting as a chemical oxidant that is continually being regenerated by reaction with hydrogen peroxide.

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