Question: The reaction \( {{\text{C}}_{6}}{{\text{H}}_{6}}+\text{C}{{\text{H}}_{3}}\xrightarrow[anhydrous]{AlC...

Question

The reaction ${{\text{C}}_{6}}{{\text{H}}_{6}}+\text{C}{{\text{H}}_{3}}\xrightarrow[anhydrous]{AlC{{l}_{3}}}\text{HCl}+{{\text{C}}_{6}}{{\text{H}}_{5}}\text{C}{{\text{H}}_{3}}$ is:
(A) Friedel-Crafts alkylation
(B) addition reaction
(C) Friedel-Crafts acylation
(D) Friedel -Crafts benzylation

Answer 1

Solution

An organic coupling reaction involving an electrophilic aromatic replacement that is used to attach substituents to aromatic rings is a Friedel-Crafts reaction. Alkylation and acylation reactions are the two primary types of Friedel-Crafts reactions.

Complete step by step solution:
It can be noted that the replacement of a hydrogen atom with an electrophile is involved in this reaction. Aluminium trichloride ( $AlC{{l}_{3}}$ ) is often used in Friedel-Crafts reactions as a catalyst because it acts as a Lewis acid and coordinates with halogens, delivering an electrophile in the process.
Friedel-Crafts Alkylation refers to an aromatic proton being replaced by an alkyl group. This is achieved using a carbocation through an electrophilic attack on the aromatic ring. A method of generating alkylbenzene by using alkyl halides as reactants is the Friedel-Crafts alkylation reaction.
To form a carbocation by facilitating the removal of the halide, a Lewis acid catalyst such as $FeC{{l}_{3}}$ or $AlC{{l}_{3}}$ is used in this reaction. Prior to proceeding with the alkylation reaction, the resulting carbocation undergoes a rearrangement.
Thus, the correct answer is option A.

Additional Information:
The French chemist Charles Friedel and the American chemist James Crafts developed these reactions in the year 1877.

Note:
There are some significant limitations to Friedel-Crafts alkylation. Since aryl and vinyl halide-formed carbocations are extremely unstable, they cannot be used in this reaction. Due to the formation of complexes, the presence of a deactivating group on the aromatic ring (such as the $N{{H}_{2}}$ group) can lead to the catalyst being deactivated. In these reactions, an excess of the aromatic compound must be used to avoid polyalkylation (addition of more than one alkyl group to the aromatic compound). In the Friedel-Crafts alkylation reaction, aromatic compounds that are less reactive than mono-halobenzene do not participate.