Thermodynamic versus kinetic reaction control

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.


*The Diels-Alder reaction of cyclopentadiene with furan serves as an example. At room temperature kinetic reaction control prevails and the less stable endo isomer 2 is the main reaction product. At 81°C and long reaction time the chemical equilibrium can assert itself and the thermodynamically stable exo isomer 1 is formed.

*In the protonation of an enolate ion the kinetic product is the enol and the thermodynamic product is a ketone.
* In carbohydrate acetalisation choice of acetone precursor determines reaction outcome.
* The electrophilic addition reaction of hydrogen bromide to 1,3-butadiene at 60°C leads predominantly to the thermodynamically stable 1,4 adduct 1-bromo-2-butene but decreasing the reaction temperature to -60°C favours the kinetic 1,2 product 3-bromo-1-butene.


* 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

Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • Control de reacción cinético y termodinámico — La distinción (también conocida como selectividad) entre las trayectorias de una reacción química controlada cinéticamente o termodinámicamente es relevante cuando el producto A se forma más rápidamente (el llamado producto cinéticamente… …   Wikipedia Español

  • electrochemical reaction — ▪ chemistry Introduction       any process either caused or accompanied by the passage of an electric current and involving in most cases the transfer of electrons between two substances one a solid and the other a liquid.       Under ordinary… …   Universalium

  • Energy — This article is about the scalar physical quantity. For other uses, see Energy (disambiguation). Energetic redirects here. For other uses, see Energetic (disambiguation) …   Wikipedia

  • Glossary of fuel cell terms — The Glossary of fuel cell terms lists the definitions of many terms used within the fuel cell industry. The terms in this glossary may be used by fuel cell industry associations, in education material and fuel cell codes and standards to name but …   Wikipedia

  • Spacecraft propulsion — A remote camera captures a close up view of a Space Shuttle Main Engine during a test firing at the John C. Stennis Space Center in Hancock County, Mississippi Spacecraft propulsion is any method used to accelerate spacecraft and artificial… …   Wikipedia

  • fluid mechanics — an applied science dealing with the basic principles of gaseous and liquid matter. Cf. fluid dynamics. [1940 45] * * * Study of the effects of forces and energy on liquids and gases. One branch of the field, hydrostatics, deals with fluids at… …   Universalium

  • Albert Einstein — Einstein redirects here. For other uses, see Einstein (disambiguation) …   Wikipedia

  • climate — /kluy mit/, n. 1. the composite or generally prevailing weather conditions of a region, as temperature, air pressure, humidity, precipitation, sunshine, cloudiness, and winds, throughout the year, averaged over a series of years. 2. a region or… …   Universalium

  • Fluorescence correlation spectroscopy — (FCS) is a common technique used by physicists, chemists, and biologists to experimentally characterize the dynamics of fluorescent species (e.g. single fluorescent dye molecules in nanostructured materials, autofluorescent proteins in living… …   Wikipedia

  • Antithrombin — Serpin peptidase inhibitor, clade C (antithrombin), member 1 Antithrombin monomer drawn from PDB 2ANT …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”