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'''Friedel–Crafts Reaction''' is a set of [[organic chemistry]] reactions developed by [[Charles Friedel]] and [[James Crafts]] in 1877. These reactions are crucial for the formation of carbon-carbon bonds, serving as a cornerstone for the synthesis of complex organic molecules. The Friedel–Crafts reactions are divided into two main types: the alkylation and the acylation reactions. Both types are employed in the synthesis of [[aromatic compounds]], making them invaluable tools in the fields of [[pharmaceuticals]], [[materials science]], and [[fine chemicals]] production.
= Friedel–Crafts Reaction =


==Friedel–Crafts Alkylation==
The '''Friedel–Crafts reaction''' is a set of reactions developed by [[Charles Friedel]] and [[James Crafts]] in 1877 to attach substituents to an [[aromatic ring]]. These reactions are of two main types: [[Friedel–Crafts alkylation]] and [[Friedel–Crafts acylation]].
The Friedel–Crafts alkylation involves the addition of an alkyl group to an aromatic ring. This reaction is typically facilitated by a [[Lewis acid]] catalyst such as aluminum chloride (AlCl3) or iron(III) chloride (FeCl3). The general mechanism involves the generation of a carbocation from the alkyl halide, which then undergoes an electrophilic aromatic substitution to form the alkylated aromatic compound.


==Friedel–Crafts Acylation==
== Friedel–Crafts Alkylation ==
In contrast, the Friedel–Crafts acylation entails the introduction of an acyl group into an aromatic ring. This reaction also requires a Lewis acid catalyst, but it uses an acyl chloride as the acylating agent. The acylation reaction is often preferred over alkylation for synthetic purposes because it avoids issues such as polyalkylation and offers better control over the product distribution.


==Mechanism==
[[File:Friedel-Crafts_Equation_Overview.svg|thumb|right|Overview of Friedel–Crafts reactions]]
Both the alkylation and acylation reactions proceed through a similar mechanism involving the activation of the alkyl halide or acyl chloride by the Lewis acid catalyst. This activation facilitates the formation of a highly reactive electrophile, which then attacks the aromatic ring to form a sigma complex. Subsequent loss of a proton restores the aromaticity, yielding the final product.


==Limitations==
The Friedel–Crafts alkylation involves the alkylation of an aromatic ring with an [[alkyl halide]] using a strong [[Lewis acid]] catalyst such as [[aluminum chloride]] (AlCl₃). This reaction is used to introduce an [[alkyl group]] into an aromatic compound.
Despite their utility, Friedel–Crafts reactions have limitations. They are typically not effective with substrates that are deactivated towards electrophilic substitution, such as nitrobenzenes. Moreover, the reactions can suffer from issues like rearrangement of the carbocation in alkylation reactions, leading to a mixture of products. Additionally, the strong Lewis acid catalysts required for these reactions can lead to side reactions or degradation of sensitive functional groups.


==Applications==
[[File:Benzene_ethylation.svg|thumb|left|Ethylation of benzene]]
The Friedel–Crafts reactions have wide-ranging applications in organic synthesis. They are used in the synthesis of important organic compounds, including [[terpenes]], [[flavonoids]], and [[alkaloids]]. In the pharmaceutical industry, these reactions are employed in the synthesis of active pharmaceutical ingredients (APIs). They also find applications in the synthesis of polymers and materials science, where the ability to construct complex carbon frameworks is invaluable.


==Environmental and Safety Considerations==
=== Mechanism ===
The use of strong Lewis acids and the generation of acidic waste pose environmental and safety concerns. Recent developments aim to mitigate these issues through the use of more environmentally benign catalysts and solvent systems.
 
The mechanism of the Friedel–Crafts alkylation involves the formation of a carbocation intermediate. The Lewis acid catalyst helps to generate the carbocation from the alkyl halide, which then attacks the aromatic ring to form the alkylated product.
 
[[File:Propylene+C6H6.svg|thumb|right|Reaction of propylene with benzene]]
 
=== Limitations ===
 
Friedel–Crafts alkylation has several limitations, including [[carbocation rearrangement]], [[polyalkylation]], and the deactivation of the aromatic ring by electron-withdrawing groups.
 
[[File:Friedel-CraftsAlkylationStericProtection.png|thumb|left|Steric protection in Friedel–Crafts alkylation]]
 
== Friedel–Crafts Acylation ==
 
The Friedel–Crafts acylation involves the acylation of an aromatic ring with an [[acyl chloride]] or [[acid anhydride]] in the presence of a Lewis acid catalyst. This reaction introduces an [[acyl group]] into the aromatic compound.
 
[[File:Friedel-Crafts-acylation-overview.png|thumb|right|Overview of Friedel–Crafts acylation]]
 
=== Mechanism ===
 
The mechanism of Friedel–Crafts acylation involves the formation of an acylium ion, which is a more stable electrophile than a carbocation. The acylium ion attacks the aromatic ring to form the acylated product.
 
=== Advantages ===
 
Friedel–Crafts acylation does not suffer from polyacylation because the acyl group is electron-withdrawing, which deactivates the aromatic ring towards further electrophilic substitution.
 
== Applications ==
 
Friedel–Crafts reactions are widely used in the synthesis of [[aromatic ketones]], [[alkylbenzenes]], and other aromatic compounds. They are important in the production of [[pharmaceuticals]], [[fragrances]], and [[polymers]].
 
[[File:Neophyl_chloride_synthesis.svg|thumb|left|Synthesis of neophyl chloride]]
 
== Related Reactions ==
 
Friedel–Crafts reactions are related to other electrophilic aromatic substitution reactions such as [[nitration]], [[sulfonation]], and [[halogenation]].
 
[[File:Friedel-Crafts-Alkylierung_2.svg|thumb|right|Example of Friedel–Crafts alkylation]]
 
== Related Pages ==


==See Also==
* [[Electrophilic aromatic substitution]]
* [[Electrophilic aromatic substitution]]
* [[Lewis acids and bases]]
* [[Aromaticity]]
* [[Organic synthesis]]
* [[Lewis acid]]
* [[Aromatic compounds]]
* [[Carbocation]]
 
[[File:1,3-Diisopropylbenzene_via_transalkylation.svg|thumb|left|Synthesis of 1,3-diisopropylbenzene via transalkylation]]


[[Category:Organic reactions]]
[[Category:Organic reactions]]
[[Category:Chemical reactions]]
[[Category:Aromatic compounds]]
[[Category:Named reactions]]
 
{{Chemistry-stub}}

Latest revision as of 14:18, 21 February 2025

Friedel–Crafts Reaction[edit]

The Friedel–Crafts reaction is a set of reactions developed by Charles Friedel and James Crafts in 1877 to attach substituents to an aromatic ring. These reactions are of two main types: Friedel–Crafts alkylation and Friedel–Crafts acylation.

Friedel–Crafts Alkylation[edit]

Overview of Friedel–Crafts reactions

The Friedel–Crafts alkylation involves the alkylation of an aromatic ring with an alkyl halide using a strong Lewis acid catalyst such as aluminum chloride (AlCl₃). This reaction is used to introduce an alkyl group into an aromatic compound.

Ethylation of benzene

Mechanism[edit]

The mechanism of the Friedel–Crafts alkylation involves the formation of a carbocation intermediate. The Lewis acid catalyst helps to generate the carbocation from the alkyl halide, which then attacks the aromatic ring to form the alkylated product.

Reaction of propylene with benzene

Limitations[edit]

Friedel–Crafts alkylation has several limitations, including carbocation rearrangement, polyalkylation, and the deactivation of the aromatic ring by electron-withdrawing groups.

Steric protection in Friedel–Crafts alkylation

Friedel–Crafts Acylation[edit]

The Friedel–Crafts acylation involves the acylation of an aromatic ring with an acyl chloride or acid anhydride in the presence of a Lewis acid catalyst. This reaction introduces an acyl group into the aromatic compound.

Overview of Friedel–Crafts acylation

Mechanism[edit]

The mechanism of Friedel–Crafts acylation involves the formation of an acylium ion, which is a more stable electrophile than a carbocation. The acylium ion attacks the aromatic ring to form the acylated product.

Advantages[edit]

Friedel–Crafts acylation does not suffer from polyacylation because the acyl group is electron-withdrawing, which deactivates the aromatic ring towards further electrophilic substitution.

Applications[edit]

Friedel–Crafts reactions are widely used in the synthesis of aromatic ketones, alkylbenzenes, and other aromatic compounds. They are important in the production of pharmaceuticals, fragrances, and polymers.

Synthesis of neophyl chloride

Related Reactions[edit]

Friedel–Crafts reactions are related to other electrophilic aromatic substitution reactions such as nitration, sulfonation, and halogenation.

Example of Friedel–Crafts alkylation

Related Pages[edit]

Synthesis of 1,3-diisopropylbenzene via transalkylation
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