Competitive chemical reactions in DC polarography: Influence of fast protonation equilibria on CE and ECE mechanisms

1991 ◽  
Vol 56 (1) ◽  
pp. 68-77 ◽  
Author(s):  
Eulogia Muñoz ◽  
José L. Avila ◽  
Juan J. Ruiz ◽  
Luis Camacho
Keyword(s):  
Kinetic Parameters ◽  
Chemical Reactions ◽  
Limiting Current ◽  
Quasi Equilibrium ◽  
Polarographic Study ◽  
Protonation Equilibria ◽  
Direct Competition ◽  
Dc Polarography ◽  
Catalytic Effects

We carried out a DC polarographic study of the limiting current for CE and ECE processes with chemical stages subject to potential catalytic effects and in direct competition with protonation reactions in quasi-equilibrium. The aforesaid competition may result in the appearance of maxima in the limiting current vs pH plots for CE mechanisms. We established the conditions required for the rise of such maxima, and developed methods for the calculation of kinetic parameters. The competition did not result in any maxima in the above-mentioned plots for ECE mechanisms; however, we established criteria for their potential identification.

Parallel Global Search Algorithm for Optimization of the Kinetic Parameters of Chemical Reactions

2021 ◽  
pp. 198-211
Author(s):  
Irek Gubaydullin ◽  
Leniza Enikeeva ◽  
Konstantin Barkalov ◽  
Ilya Lebedev
Keyword(s):  
Kinetic Parameters ◽  
Chemical Reactions ◽  
Search Algorithm ◽  
Global Search ◽  
Global Search Algorithm

Polarographic Study of the Electrode Reaction of Zn(II) in Formamide and Dimethylformamide

1975 ◽  
Vol 30 (5-6) ◽  
pp. 350-354 ◽  
Author(s):  
Sudhindra Swarup Sharma ◽  
Mukhtar Singh
Keyword(s):  
Kinetic Parameters ◽  
Organic Solvents ◽  
Metal Ion ◽  
Supporting Electrolyte ◽  
Electrode Reaction ◽  
Polarographic Study ◽  
Aqueous Mixtures ◽  
Diffusion Controlled ◽  
And Diffusion

The reduction of Zn(II) at the d.m.e. has been studied in aqueous mixtures of formamide and dimethylformamide. The general polarographic characteristics have been determined, using 0.1 M NaNO3 as the supporting electrolyte. The reduction of Zn(II) in these organic solvents is irreversible and diffusion controlled. The kinetic parameters, αna and kf,h have been calculated separately by KOTECKY and DELAHAY treatments. The change of polarographic characteristics and kinetic parameters is explained in terms of solvation of the metal ion in these solvents. The electrocapillary curves in the presence of these solvents have also been studied.

scholarly journals Kinetic parameters of the acyl-enzyme mechanism and conditions for quasi-equilibrium and for optimal catalytic characteristics

1990 ◽  
Vol 270 (2) ◽  
pp. 561-563 ◽  
Author(s):  
K Brocklehurst ◽  
C M Topham
Keyword(s):  
Kinetic Parameters ◽  
Enzyme Mechanism ◽  
Quasi Equilibrium

scholarly journals Design principles of autocatalytic cycles constrain enzyme kinetics and force low substrate saturation at flux branch points

2016 ◽  
Author(s):  
Uri Barenholz ◽  
Dan Davidi ◽  
Ed Reznik ◽  
Yinon Bar-On ◽  
Niv Antonovsky ◽  
...  
Keyword(s):  
Kinetic Parameters ◽  
Chemical Reactions ◽  
Carbon Metabolism ◽  
Quantitative Proteomics ◽  
Central Carbon Metabolism ◽  
Branch Points ◽  
The Core ◽  
Intermediate Metabolites ◽  
Central Carbon ◽  
Substrate Saturation

AbstractA set of chemical reactions that require a metabolite to synthesize more of that metabolite is an autocatalytic cycle. Here we show that most of the reactions in the core of central carbon metabolism are part of compact autocatalytic cycles. Such metabolic designs must meet specific conditions to support stable fluxes, hence avoiding depletion of intermediate metabolites. As such, they are subjected to constraints that may seem counter-intuitive: the enzymes of branch reactions out of the cycle must be overexpressed and the affinity of these enzymes to their substrates must be relatively weak. We use recent quantitative proteomics and fluxomics measurements to show that the above conditions hold for functioning cycles in central carbon metabolism of E.coli. This work demonstrates that the topology of a metabolic network can shape kinetic parameters of enzymes and lead to seemingly wasteful enzyme usage.

Determination of the basis for nonlinear parametric functions of chemical reactions

2020 ◽  
pp. 29-34
Author(s):  
Зульфия Абударовна Хамидуллина ◽  
Альбина Сабирьяновна Исмагилова ◽  
Семен Израилевич Спивак
Keyword(s):  
Kinetic Parameters ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Computer Modelling ◽  
Theoretical Interpretation ◽  
Structural Mechanism ◽  
Complex Chemical ◽  
Complex Chemical Reaction ◽  
Complex Chemical Reactions ◽  
Parametric Functions

Настоящая работа посвящена математическому и компьютерному моделированию кинетики сложных химических реакций. Сформулирована и доказана теорема о соответствии структуры механизма сложной химической реакции с матрицей связей. Разработан и автоматизирован алгоритм определения базиса нелинейных параметрических функций. Реализована теоретико-графовая интерпретация механизма сложной химической реакции Mathematical and computer modelling of the kinetics of complex chemical reactions is considered in the present study. It was formulated that the structural mechanism of complex chemical reaction corresponds to the matrix of bonds. The appropriate theorem was proved. A graph and theoretical technique that allows determining the functional dependences of kinetic parameters directly from the graph of the reaction mechanism is developed. Based on the proposed algorithm, a program for determining the basis of nonlinear parametric functions of kinetic parameters is proposed. The program implements a graph and theoretic interpretation of the mechanisms of complex chemical reactions for constructing stationary kinetic models of catalytic reactions. An algorithm for determining the basis of nonlinear parametric functions is developed and automated. A graph and theoretical interpretation of the mechanism of a complex chemical reaction is implemented

Factors influencing the limiting current in pulse polarography

1987 ◽  
Vol 52 (3) ◽  
pp. 587-591
Author(s):  
Jorge A. Bolzan
Keyword(s):  
Time Delay ◽  
Pulse Width ◽  
Adsorption Kinetic ◽  
Limiting Current ◽  
Powerful Technique ◽  
Factors Influencing ◽  
Pulse Polarography ◽  
Dc Polarography ◽  
Mercury Column ◽  
Catalytic Processes

The variation of the limiting current as a function of h, the corrected height of the mercury column, and t, the time delay plus pulse width, are studied and compared with the similar relationships of DC polarography. Diffusion, adsorption, kinetic and catalytic processes are examined. Though pulse polarography is in almost every respect a much more powerful technique than DC polarography, it is shown that while the latter allows a distinction to be drawn between the different processes, by using the above mentioned relationships, the former is not suitable for the same purpose.

scholarly journals A simple and effective method for the accurate extraction of kinetic parameters using differential Tafel plots

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Prashant Khadke ◽  
Tim Tichter ◽  
Tim Boettcher ◽  
Falk Muench ◽  
Wolfgang Ensinger ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Kinetic Parameters ◽  
Correction Method ◽  
Limiting Current ◽  
Accurate Estimation ◽  
Research Groups ◽  
First Order ◽  
Straight Line ◽  
Charging Current ◽  
Definition Of

AbstractThe practice of estimating the transfer coefficient ($$\alpha$$ α ) and the exchange current ($${i}_{0}$$ i 0 ) by arbitrarily placing a straight line on Tafel plots has led to high variance in these parameters between different research groups. Generating Tafel plots by finding kinetic current, $${i}_{k}$$ i k from the conventional mass transfer correction method does not guarantee an accurate estimation of the $$\alpha$$ α and $${i}_{0}$$ i 0 . This is because a substantial difference in values of $$\alpha$$ α and $${i}_{0}$$ i 0 can arise from only minor deviations in the calculated values of $${i}_{k}$$ i k . These minor deviations are often not easy to recognise in polarisation curves and Tafel plots. Recalling the IUPAC definition of $$\alpha$$ α , the Tafel plots can be alternatively represented as differential Tafel plots (DTPs) by taking the first order differential of Tafel plots with respect to overpotential. Without further complex processing of the existing raw data, many crucial observations can be made from DTP which is otherwise very difficult to observe from Tafel plots. These for example include a) many perfectly looking experimental linear Tafel plots (R2 > 0.999) can give rise to incorrect kinetic parameters b) substantial differences in values of $$\alpha$$ α and $${i}_{0}$$ i 0 can arise when the limiting current ($${i}_{L}$$ i L ) is just off by 5% while performing the mass transfer correction c) irrespective of the magnitude of the double layer charging current ($${i}_{\mathrm{c}}$$ i c ), the Tafel plots can still get significantly skewed when the ratio of $${i}_{0}/{i}_{c}$$ i 0 / i c is small. Hence, in order to determine accurate values of $$\alpha$$ α and $${i}_{0}$$ i 0 , we show how the DTP approach can be applied to experimental polarisation curves having well defined $${i}_{L}$$ i L , poorly defined $${i}_{L}$$ i L and no $${i}_{L}$$ i L at all.

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