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Radical substitution

In organic chemistry, a radical-substitution reaction is a substitution reaction involving free radicals as a reactive intermediate.March Jerry; (1985). Advanced organic chemistry reactions, mechanisms and structure (3rd ed.). New York: John Wiley & Sons, inc. The reaction always involves at least two steps, and possibly a third. In the first step called initiation (2,3) a free radical is created by homolysis. Homolysis can be brought about by heat or ultraviolet light but also by radical initiators such as organic peroxides or azo compounds. UV Light is used to create two free radicals from one diatomic species. The final step is called termination (6,7) in which the radical recombines with another radical species. If the reaction is not terminated, but instead the radical group(s) go on to react further, the steps where new radicals are formed and then react is collectively known as propagation (4,5) because a new radical is created available for secondary reactions.

Radical substitution reactions

In free radical halogenation reactions radical substitution takes place with halogen reagents and alkane substrates. Another important class of radical substitutions involve aryl radicals. One example is the hydroxylation of benzene by Fenton's reagent. Many oxidation and reduction reactions in organic chemistry have free radical intermediates, for example the oxidation of aldehydes to carboxylic acids with chromic acid. Coupling reactions can also be considered radical substitutions. Certain aromatic substitutions takes place by radical-nucleophilic aromatic substitution. Auto-oxidation is a process responsible for deterioration of paints and food and lab hazards such as diethyl ether peroxide. More radical substitutions are listed below:

References

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This article based upon the http://en.wikipedia.org/wiki/Radical_substitution, the free encyclopaedia Wikipedia and is licensed under the GNU Free Documentation License.
Further informations available on the list of authors and history: http://en.wikipedia.org/w/index.php?title=Radical_substitution&action=history
presented by: Ingo Malchow, Mirower Bogen 22, 17235 Neustrelitz, Germany