Friedel Craft acylation Reaction

Friedel Craft acylation Reaction

In this Friedel craft acylation reaction Arenes, an acyl group is introduced on the benzene or arene ring by using the acyl halide in presence of anhydrous AlCl₃. The reagents can be represented as

1. _{Anhydrous AlCl3}
2. Anhydrous FeCl₃
3. BF₃
4. TiCl₃
5. ZnCl₂
6. SnCl₄

The mechanism of the reaction starts with the formation of an Acyl carbonium ion. Acyl halide reacts with anhydrous AlCl3 and acts as a halogen carrier to produce an acyl carbonium ion (electrophile).

The acyl carbonium ion formed reacts with an aromatic ring to produce resonating forms of the arene. This positive charge on the aromatic ring a stabilized by resonating forms.
In resonance hybrid structure the positive charges are distributed over five carbon atoms so relative positive charge density on each carbon atom is very less and thus it is stabilized.

The structure three formed in the resonating forms further stabilizes to give a mono-substituted acyl derivative.

The H+ ion release in this reaction joins with the conjugate base to form a byproduct.

The monosubstituted derivative of arenes uses an acyl halide to give the monosubstituted derivative. While deciding the products of acylation the alkyl group selection decides the product formed.

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