Radical substitution
This article will address the topic of Radical substitution, which represents a fundamental aspect in the _var2 scope. Throughout history, Radical substitution has held a prominent place in society, playing a crucial role in _var3. Through a comprehensive analysis, the evolution of Radical substitution will be examined, as well as its implications in different areas such as _var4, _var5 and _var6. Various points of view from experts on the topic will be explored, with the aim of providing a comprehensive perspective that allows us to understand the importance and relevance of Radical substitution today. Through a multidisciplinary approach, the aim is to offer readers a complete and updated vision of Radical substitution, with the purpose of generating an enriching debate and promoting greater understanding of this significant topic.
In organic chemistry, a radical-substitution reaction is a substitution reaction involving free radicals as a reactive intermediate.[1]
The reaction always involves at least two steps, and possibly a third.
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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 are collectively known as propagation (4,5). This is because a new radical is created, able to participate in 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, as well as production of certain lab hazards such as diethyl ether peroxide.
More radical substitutions are listed below:
- The Barton–McCombie deoxygenation involves substitution of a hydroxyl group for a proton.
- The Wohl–Ziegler reaction involves allylic bromination of alkenes.
- The Hunsdiecker reaction converts silver salts of carboxylic acids to alkyl halides.
- The Dowd–Beckwith reaction involves ring expansion of cyclic β-keto esters.
- The Barton reaction involves synthesis of nitrosoalcohols from nitrites.
- The Minisci reaction involves generation of an alkyl radical from a carboxylic acid and a silver salt, and subsequent substitution at an aromatic compound
References
- ^ March Jerry; (1985). Advanced organic chemistry reactions, mechanisms and structure (3rd ed.). New York: John Wiley & Sons, inc. ISBN 0-471-85472-7
- ^ Ashenhurst, James (6 September 2013). "Initiation, Propagation, Termination". Master Organic Chemistry. Retrieved 3 November 2025.