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Reaction intermediate

The IUPAC Gold Book[1] defines a reaction intermediate or an intermediate as a molecular entity (atom, ion, molecule...) with a lifetime appreciably longer than a molecular vibration (corresponding to a local potential energy minimum of depth greater than RT; R being the gas constant and T is temperature) that is formed (directly or indirectly) from the reactants and reacts further to give (either directly or indirectly) the products of a chemical reaction.

Most chemical reactions are stepwise, that is they take more than one elementary step to complete. An intermediate is the reaction product of each of these steps (except for the last one, which forms the final product).

For example in a hypothetical stepwise reaction:

A + 2B → C + D + E,

That includes these elementary steps:

A + B → C + X
X → D + Y
B + Y → E

The chemical species X and Y are intermediates.

Reactive intermediates are usually short lived and are very seldom isolated


The main carbon reactive intermediates

Common features of carbon intermediates

Other reactive intermediates


  • Carey,Francis A.; Sundberg, Richard J.; (1984). Advanced Organic ChemistryPart A Structure and Mechanisms (2nd ed.). New York N.Y.: Plenum Press.ISBN 0-306-41198-9.
  • MarchJerry; (1885). Advanced Organic Chemistry reactions, mechanisms andstructure (3rd ed.). New York: John Wiley & Sons, inc. ISBN 0-471-85472-7
  • Gilchrist T.C.;Rees C.W.; (1969) carbenes, nitrenes and arynes. Nelson. London.


  1. ^ IUPAC Goldbook definition of intermediate
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Reaction_intermediate". A list of authors is available in Wikipedia.
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