Friedel-Crafts Acylation is a pivotal reaction in organic chemistry, enabling the introduction of acyl groups into aromatic compounds like benzene. This process, catalyzed by Lewis acids such as AlCl3, is essential for synthesizing pharmaceuticals, polymers, and other industrial chemicals. It offers advantages over Alkylation by preventing over-reactivity and carbocation rearrangement, making it a preferred method for creating aromatic ketones.
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Friedel-Crafts Acylation is a reaction that introduces an acyl group into an aromatic ring through an electrophilic aromatic substitution mechanism
Friedel-Crafts Acylation was discovered by Charles Friedel and James Crafts in 1877 and is typically catalyzed by Lewis acids such as aluminum chloride or ferric chloride
The Friedel-Crafts Acylation mechanism involves several stages, including the formation of an acylium ion and electrophilic aromatic substitution
An acyl halide reacts with a Lewis acid to generate an acylium ion, which is highly reactive and initiates the subsequent steps of the reaction
The acylium ion undergoes electrophilic aromatic substitution with an aromatic ring, forming a resonance-stabilized carbocation intermediate
The intermediate is then deprotonated by an AlCl4- ion, resulting in the formation of an aromatic ketone product and the release of HCl
Friedel-Crafts Acylation introduces an acyl group, while Friedel-Crafts Alkylation introduces an alkyl group, making them distinct methods for modifying aromatic rings
Acylation is preferred over Alkylation to prevent poly-substitution, over-reactivity, and carbocation rearrangement
Benzene is a typical substrate for Friedel-Crafts Acylation, resulting in the synthesis of a diverse array of aromatic ketones with significant industrial value
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Friedel-Crafts Acylation catalysts
Typically Lewis acids like AlCl3 or FeCl3, catalyze the reaction by forming a complex with acyl chloride.
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Electrophile in Friedel-Crafts Acylation
Acylium ion, formed from acyl chloride and Lewis acid, is the highly electrophilic species that reacts with the aromatic ring.
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Product of Friedel-Crafts Acylation
An acylated aromatic compound, where a hydrogen atom on the aromatic ring is replaced by an acyl group.
