Question

What is Friedel-Crafts alkylation and Friedel-Crafts acylation reactions? Explain with examples

Answer 1

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✧ $\sf\green{Friedel\: - \: Crafts \: Alkylation :}$

⇝Friedel-Crafts Alkylation refers to the replacement of an aromatic proton with an alkyl group.

⇝This is done through an electrophilic attack on the aromatic ring with the help of a carbocation.

⇝The Friedel-Crafts alkylation reaction is a method of generating alkylbenzenes by using alkyl halides as reactants.

↝$\sf\blue{Example:}$

➛ the addition of a methyl group to a benzene ring.

➛ The mechanism for this reaction begins with the generation of a methyl carbocation from methylbromide

✧ $\sf\green{Friedel\: - \: Crafts\: Acylation :}$

⇝The Friedel-Crafts acylation reaction involves the addition of an acyl group to an aromatic ring.

⇝The halogen belonging to the acyl halide forms a complex with the Lewis acid, generating a highly electrophilic acylium ion, which has a general formula of RCO+ and is stabilized by resonance.

↝$\sf\blue{Example:}$

➛ The reaction of acetyl chloride with aluminum chloride forms an electrophile.

➛ The electrophile attracts the π electron system of the benzene ring to form a nonaromatic carbocation.

➛ The positive charge on the carbocation that is formed is delocalized throughout the molecule.

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