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Thermodynamic versus kinetic reaction control



Thermodynamic reaction control or kinetic reaction control in a chemical reaction can decide the composition in a reaction product when competing reactions lead to different products under different reaction conditions. The distinction is relevant when product A forms faster (kinetics) than product B (The activation energy for A is lower than that of B) but B is a more stable (thermodynamics) product than A.

Reactions are considered to take place under thermodynamic reaction control when the reverse reaction is rapid and the Chemical equilibrium establishes itself quickly. In this way the thermodynamically more stable product is always favoured. Thermodynamic reaction control takes place with vigorous reaction conditions or when the reaction is allowed to continue over a long time to give a slow reaction time to reach equilibrium.

In kinetic reaction control, the forward reaction is much faster than the reverse reaction. As a result, the reaction favours the product with the lowest activation energy and goes forth regardless of relative product stabilities. Kinetic control is favoured with mild and low temperature conditions.

Examples

References

  • Organic Chemistry, 3rd ed., M. A. Foxe & J. K. Whitesell, Jones & Bartlett, 2004 ISBN 0-7637-2197-2
  • A Guidebook to Mechanism in Organic Chemistry, 6th Edition, Peter Sykes, Pearson Prentice Hall, 1986. ISBN 0-582-44695-3
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Thermodynamic_versus_kinetic_reaction_control". A list of authors is available in Wikipedia.
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