Chemical Kinetics

2021 ◽  
pp. 228-254
Author(s):  
Christopher O. Oriakhi
Keyword(s):  
Activation Energy ◽  
Chemical Kinetics ◽  
Chemical Reactions ◽  
Half Life ◽  
Reaction Rates ◽  
Effect Of Temperature ◽  
Collision Theory ◽  
Rate Laws ◽  
Reaction Orders

Chemical Kinetics discusses the rate at which chemical reactions occur and how these rates can be expressed mathematically, with a review of the factors which affect reaction rates. Topics presented with a numerical focus include reaction rate measurements, rate laws and their components including rate constants, determination of reaction orders from integrated rate laws, and effects of temperature on rates. Reaction half life and its determination are discussed. Collision theory, which forms the basis of the rate law, is presented with emphasis on the effect of temperature on the rate constant and the rate. The Arrhenius equation and the concept of activation energy are discussed with illustrative calculations for determining the energy of activation.

scholarly journals A General Fitting Function to Estimate Apparent Reaction Orders of Kinetic Profiles

2019 ◽  
Author(s):  
Robert Pollice
Keyword(s):  
Chemical Reactions ◽  
Catalyst Deactivation ◽  
Rapid Development ◽  
Product Inhibition ◽  
Time Profile ◽  
Time Data ◽  
Concentration Time ◽  
Wide Range ◽  
Reaction Orders

The rapid development of analytical methods in recent decades has resulted in a wide range of readily available and accurate reaction-monitoring techniques, which allow for easy determination of high-quality concentration-time data of chemical reactions. However, while the acquisition of kinetic data has become routine in the development of new chemical reactions and the study of their mechanisms, not all the information contained therein is utilized because of a lack of suitable analysis tools which unnecessarily complicates mechanistic studies. Herein, we report on a general method to analyze a single concentration-time profile of chemical reactions and extract information regarding the reaction order with respect to substrates, the presence of multiple kinetic regimes, and the presence of kinetic complexities, such as catalyst deactivation, product inhibition, and substrate decomposition.<br>

Determination of Activation Energy of the Iron Acceptor Pair Association and Dissociation Reaction

2015 ◽  
Vol 242 ◽  
pp. 230-235
Author(s):  
Kevin Lauer ◽  
Christian Möller ◽  
D. Debbih ◽  
Manuel Auge ◽  
Dirk Schulze
Keyword(s):  
Activation Energy ◽  
Iron Content ◽  
Reaction Rates ◽  
Activation Energies ◽  
Illumination Intensity ◽  
Dissociation Reaction ◽  
Acceptor Pair ◽  
Association Reaction

A method to measure the reaction rates of the iron acceptor pair association and dissociation is presented and applied. The activation energies of the dissociation and association reaction are determined for the acceptors boron, aluminum, gallium and indium. Additionally, the activation energies are reported for different illumination intensities. It is found that the activation energy of the association reaction varies for the investigated acceptors and that the activation energy of the dissociation reaction depends strongly on the illumination intensity. It is shown that neglecting of the dissociation reaction in the evaluation of relative interstitial iron content decrease causes a considerable overestimation of the activation energy of the iron acceptor association.

scholarly journals On the theory of time dilation in chemical kinetics

2017 ◽  
Vol 31 (26) ◽  
pp. 1750177
Author(s):  
Mirza Wasif Baig
Keyword(s):  
Transition State ◽  
Chemical Kinetics ◽  
Chemical Reactions ◽  
Lorentz Transformation ◽  
Half Life ◽  
Special Theory ◽  
Time Dilation ◽  
Theory Of Relativity ◽  
Special Theory Of Relativity ◽  
Methylamine Dehydrogenase

The rates of chemical reactions are not absolute but their magnitude depends upon the relative speeds of the moving observers. This has been proved by unifying basic theories of chemical kinetics, which are transition state theory, collision theory, RRKM and Marcus theory, with the special theory of relativity. Boltzmann constant and energy spacing between permitted quantum levels of molecules are quantum mechanically proved to be Lorentz variant. The relativistic statistical thermodynamics has been developed to explain quasi-equilibrium existing between reactants and activated complex. The newly formulated Lorentz transformation of the rate constant from Arrhenius equation, of the collision frequency and of the Eyring and Marcus equations renders the rate of reaction to be Lorentz variant. For a moving observer moving at fractions of the speed of light along the reaction coordinate, the transition state possess less kinetic energy to sweep translation over it. This results in the slower transformation of reactants into products and in a stretched time frame for the chemical reaction to complete. Lorentz transformation of the half-life equation explains time dilation of the half-life period of chemical reactions and proves special theory of relativity and presents theory in accord with each other. To demonstrate the effectiveness of the present theory, the enzymatic reaction of methylamine dehydrogenase and radioactive disintegration of Astatine into Bismuth are considered as numerical examples.

Analysis of chemical reaction systems by means of network thermodynamics

1989 ◽  
Vol 54 (9) ◽  
pp. 2335-2344
Author(s):  
José Horno ◽  
Carlos F. González-Fernández
Keyword(s):  
Steady State ◽  
Chemical Kinetics ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Reaction Rates ◽  
Rate Equations ◽  
Mathematical Treatment ◽  
Reaction Systems ◽  
Chemical Reaction Systems ◽  
Simple Network

The simple network thermodynamics approach is applied to chemical reaction systems, whereby chemical reactions can be studied avoiding complex mathematical treatment. Steady state reaction rates are obtained for two chemical reaction systems, viz. the decomposition of ozone and the reaction of hydrogen with bromine. The rate equations so obtained agree with those derived from the chemical kinetics concept.

Chemical Kinetics

2009 ◽  
Author(s):  
Christopher O. Oriakhi
Keyword(s):  
Chemical Kinetics ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Kinetic Data ◽  
Average Rate ◽  
Reaction Rates ◽  
Instantaneous Rate ◽  
Rate Of Reaction ◽  
Line Tangent ◽  
The Given

Chemical kinetics is the aspect of chemistry that deals with the speed or rate of chemical reactions and the mechanisms by which they occur. The rate of a chemical reaction is a measure of how fast the reaction occurs, and it is defined as the change in the amount or concentration of a reactant or product per unit time. The mechanism of a reaction is the series of steps or processes through which it occurs. Most experimental techniques for determining reaction rates involve measuring of the rate of disappearance of a reactant, or the rate of appearance of a product. For a reaction in which the reactant Y is converted to some products: Rate = Concentration of Y at time t2 −Concentration of Y at time t1/t2 −t1 Rate = Δ [Y]/ Δt where [Y] indicates the molar concentration of the reactant of interest, and Δ refers to a change in the given amount. Rate for a reactant, by this definition, is a negative number. For a product, it is positive. The value of the rate at a particular time is known as the instantaneous rate and will be different from the average rate. Its value can be obtained from the plot of concentration (mol/L) vs. time (s) as the slope of a line tangent to the curve at a given point. Consider the following kinetic data for the decomposition of N2O5 to gaseous NO2 and O2 at 40°C (see table 16-3). A plot of [N2O5] vs. time is shown in figure 16-2. From this curve, the instantaneous rate of reaction at any time t can be obtained from the slope of the tangent to the curve. This corresponds to the value of Δ [N2O5]/ Δt for the tangent at a given instant. The instantaneous rate at the beginning of the reaction (t =0) is known as the initial rate.

6. Changing the identity of matter

2014 ◽  
pp. 86-105
Author(s):  
Peter Atkins
Keyword(s):  
Activation Energy ◽  
Reaction Mechanism ◽  
Equilibrium Constant ◽  
Chemical Kinetics ◽  
Chemical Reactions ◽  
Chemical Dynamics ◽  
Rate Determining Step ◽  
Constant Rate ◽  
Key Terms ◽  
Spontaneous Reaction

A great deal of chemistry is concerned with changing the identity of matter by the deployment of chemical reactions. Physical chemists are interested in a variety of aspects of chemical reactions, including the rates at which they take place (chemical kinetics) and the details of the steps involved during the transformation (chemical dynamics). Chemical reactions can be achieved simply by mixing and heating, but some are stimulated by light (photochemistry) and others by electricity (electrochemistry). ‘Changing the identity of matter’ explains the key terms of chemical kinetics and chemical dynamics such as spontaneous reaction, reaction quotient, equilibrium constant, rate law, reaction mechanism, rate-determining step, activation energy, and catalysis.

scholarly journals A General Fitting Function to Estimate Apparent Reaction Orders of Kinetic Profiles

2019 ◽  
Author(s):  
Robert Pollice
Keyword(s):  
Chemical Reactions ◽  
Catalyst Deactivation ◽  
Rapid Development ◽  
Product Inhibition ◽  
Time Profile ◽  
Time Data ◽  
Concentration Time ◽  
Wide Range ◽  
Reaction Orders

The rapid development of analytical methods in recent decades has resulted in a wide range of readily available and accurate reaction-monitoring techniques, which allow for easy determination of high-quality concentration-time data of chemical reactions. However, while the acquisition of kinetic data has become routine in the development of new chemical reactions and the study of their mechanisms, not all the information contained therein is utilized because of a lack of suitable analysis tools which unnecessarily complicates mechanistic studies. Herein, we report on a general method to analyze a single concentration-time profile of chemical reactions and extract information regarding the reaction order with respect to substrates, the presence of multiple kinetic regimes, and the presence of kinetic complexities, such as catalyst deactivation, product inhibition, and substrate decomposition.<br>

Development of HPLC Method for the Purity Test by Design of Experiments and Determination of Activation Energy of Hydrolytic Degradation Reactions of Sofosbuvir

2020 ◽  
Vol 16 (7) ◽  
pp. 976-987
Author(s):  
Jakub Petřík ◽  
Jakub Heřt ◽  
Pavel Řezanka ◽  
Filip Vymyslický ◽  
Michal Douša
Keyword(s):  
Activation Energy ◽  
Design Of Experiments ◽  
Mobile Phase ◽  
Hydrolytic Degradation ◽  
Isoconversional Method ◽  
Hplc Method ◽  
Organic Modifier ◽  
Calculation Methods ◽  
Degradation Reactions

Background: The present study was focused on the development of HPLC method for purity testing of sofosbuvir by the Design of Experiments and determination of the activation energy of hydrolytic degradation reactions of sofosbuvir using HPLC based on the kinetics of sofosbuvir degradation. Methods: Following four factors for the Design of Experiments were selected, stationary phase, an organic modifier of the mobile phase, column temperature and pH of the mobile phase. These factors were examined in two or three level experimental design using Modde 11.0 (Umetrics) software. The chromatographic parameters like resolution, USP tailing and discrimination factor were calculated and analysed by partial least squares. The chromatography was performed based on Design of Experiments results with the mobile phase containing ammonium phosphate buffer pH 2.5 and methanol as an organic modifier. Separation was achieved using gradient elution on XBridge BEH C8 at 50 °C and a flow rate of 0.8 mL/min. UV detection was performed at 220 nm. The activation energy of hydrolytic degradation reactions of sofosbuvir was evaluated using two different calculation methods. The first method is based on the slope of dependence of natural logarithm of the rate constant on inverted thermodynamic temperature and the second approach is the isoconversional method. Results and Conclusion: Calculated activation energies were 77.9 ± 1.1 kJ/mol for the first method and 79.5 ± 3.2 kJ/mol for the isoconversional method. The results can be considered to be identical, therefore both calculation methods are suitable for the determination of the activation energy of degradation reactions.

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