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Energy profile diagram for kinetic versus thermodynamic product reaction. Thermodynamic reaction control or kinetic reaction control in a chemical reaction can decide the composition in a reaction product mixture when competing pathways lead to different products and the reaction conditions influence the selectivity or stereoselectivity.
A reaction coordinate diagram can also be used to qualitatively illustrate kinetic and thermodynamic control in a reaction. Figure 9:Kinetic and Thermodynamic Control: A. Product B is both the kinetic and thermodynamic product and B. Product A is the kinetic product while B is the thermodynamic product. [4]
At 298 K, a reaction with ΔG ‡ = 23 kcal/mol has a rate constant of k ≈ 8.4 × 10 −5 s −1 and a half life of t 1/2 ≈ 2.3 hours, figures that are often rounded to k ~ 10 −4 s −1 and t 1/2 ~ 2 h. Thus, a free energy of activation of this magnitude corresponds to a typical reaction that proceeds to completion overnight at room ...
Chemical kinetics, also known as reaction kinetics, is the branch of physical chemistry that is concerned with understanding the rates of chemical reactions. It is different from chemical thermodynamics, which deals with the direction in which a reaction occurs but in itself tells nothing about its rate.
The ideal kinetic resolution is that in which only one enantiomer reacts, i.e. k R >>k S. The selectivity (s) of a kinetic resolution is related to the rate constants of the reaction of the R and S enantiomers, k R and k S respectively, by s=k R /k S, for k R >k S. This selectivity can also be referred to as the relative rates of reaction.
The main feature of thermodynamic diagrams is the equivalence between the area in the diagram and energy. When air changes pressure and temperature during a process and prescribes a closed curve within the diagram the area enclosed by this curve is proportional to the energy which has been gained or released by the air.
In chemistry, chemical stability is the thermodynamic stability of a chemical system, in particular a chemical compound or a polymer. [1] Colloquially, it may instead refer to kinetic persistence , the shelf-life of a metastable substance or system; that is, the timescale over which it begins to degrade.
In a multistep reaction, the rate-determining step does not necessarily correspond to the highest Gibbs energy on the reaction coordinate diagram. [ 8 ] [ 6 ] If there is a reaction intermediate whose energy is lower than the initial reactants, then the activation energy needed to pass through any subsequent transition state depends on the ...