Kinetic control AND thermodynamic control
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I have a question for everyone! How can one determine whether a reaction is controlled by kinetics or thermodynamics? What are the characteristics of kinetically controlled reactions and thermodynamically controlled reactions? What are some common reactions controlled by kinetics and thermodynamics? Is the reaction between 2-methyl-1-butene and methanol to form TAME kinetically or thermodynamically controlled? How to understand it?
:victory: It seems like you’re a bit confused about some basic theoretical concepts! It is recommended to read more books! Kinetic control is a matter of speed. Any method that can change the speed can also alter dynamic control, such as temperature, pressure, and so on! ! Thermodynamic control is a balance problem, meaning that the rate is irrelevant. For example, under normal conditions, it is thermodynamically feasible for oxygen and hydrogen to react, but they simply do not react (due to an excessively slow kinetic rate!) ）
Kinetic control should be related to concentration; another factor is the influence of temperature； Thermodynamic control should be related only to Gibbs free energy, that is, to temperature.
Calculating the Gibbs free energy of the reaction shows that if it is much smaller than 0 (for example, negative by hundreds of kJ per mole), the reaction is irreversible; if no reaction occurs or the reaction proceeds slowly, it is kinetically controlled； A balance exists near 0 (which can be positive or negative), and it is under thermodynamic control ； Values much greater than 0 show no reaction.
Dynamic control is also closely related to the catalyst. Gibbs free energy is related to pressure as well, and pressure affects equilibrium
For the simple reactions cited by LZ, thermodynamic control mainly pertains to the equilibrium constraints of reversible reactions. Specifically, the reaction equilibrium constant can be determined using the data on reaction Gibbs free energy, and thereby the equilibrium conversion rate of the reaction can be calculated under certain feed composition conditions. If the reaction conversion is lower than the equilibrium conversion, the reaction is kinetically controlled; if it is close to the equilibrium conversion, the reaction is thermodynamically controlled. For complex reaction systems, the impact on selectivity also needs to be considered, making things more complicated.