# Concerted reaction

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{{short description|Chemical reaction in which all bond reformation occurs in one step}}
{{redirect|Concerted|the organization|Concerted (organization)}}
[[File:Sn2EtCl+bromide.png|thumb|[S{{sub|N}}2](/source/SN2) reaction of a [bromide ion](/source/bromide_ion) with [chloroethane](/source/chloroethane) showing the concerted nature of the reaction, the transition state and the predictable [stereochemistry](/source/stereochemistry) through [Walden inversion](/source/Walden_inversion).]]

In [chemistry](/source/chemistry), a '''concerted reaction''' is a [chemical reaction](/source/chemical_reaction) in which all [bond](/source/Chemical_bond) breaking and bond making occurs in a single [step](/source/Reaction_step). [Reactive intermediate](/source/Reactive_intermediate)s or other unstable high energy intermediates are not involved.<ref>Carey, Francis A.; Sundberg, Richard J.; (1984). Advanced Organic Chemistry Part A Structure and Mechanisms (2nd ed.). New York N.Y.: Plenum Press. {{ISBN|0-306-41198-9}}.</ref><ref>{{Cite journal|url = http://goldbook.iupac.org/CT07011.html|title = IUPAC Gold Book - concerted reaction|doi = 10.1351/goldbook.CT07011|date = 24 February 2014|accessdate = 12 April 2014|publisher = [IUPAC](/source/IUPAC)|doi-access = free|url-access = subscription}}</ref> Concerted [reaction rate](/source/reaction_rate)s tend not to depend on [solvent](/source/solvent) [polarity](/source/Chemical_polarity) ruling out large buildup of [charge](/source/electrical_charge) in the [transition state](/source/transition_state). The reaction is said to progress through a '''concerted mechanism''' as all bonds are formed and broken ''in concert''. [Pericyclic](/source/Pericyclic) reactions, the [S{{sub|N}}2](/source/SN2) reaction, and some [rearrangements](/source/Rearrangement_reaction) - such as the [Claisen rearrangement](/source/Claisen_rearrangement) - are concerted reactions.

The rate of the S<sub>N</sub>2 reaction is second order overall due to the reaction being [bimolecular](/source/bimolecular) (i.e. there are two molecular species involved in the [rate-determining step](/source/rate-determining_step)). The reaction does not have any intermediate steps, only a [transition state](/source/transition_state). This means that all the bond making and bond breaking takes place in a single step. In order for the reaction to occur both molecules must be situated correctly.

==References==
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Category:Organic reactions

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Adapted from the Wikipedia article [Concerted reaction](https://en.wikipedia.org/wiki/Concerted_reaction) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Concerted_reaction?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.