Statement-1 Alkylation of benzene by Friedel -Crafts reaction gives polyalkylated benzene.Statement-2 The ring gets activated for further substitution after the introduction of one alkyl group.a)Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1.b)Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1c)Statement-1 is True, Statement-2 is Falsed)Statement-1 is False, Statement-2 is TrueCorrect answer is option 'A'. Can you explain this answer?

Question

Answer

Statement-1: Alkylation of benzene by Friedel-Crafts reaction gives polyalkylated benzene.

The Friedel-Crafts alkylation reaction involves the substitution of a hydrogen atom on an aromatic ring with an alkyl group. In this reaction, an alkyl halide reacts with a Lewis acid catalyst, usually aluminum chloride (AlCl3), to form a carbocation intermediate. The carbocation then reacts with the aromatic ring to form a new carbon-carbon bond, resulting in the addition of an alkyl group to the benzene ring.

Statement-2: The ring gets activated for further substitution after the introduction of one alkyl group.

After the introduction of one alkyl group through Friedel-Crafts alkylation, the benzene ring becomes activated for further substitution reactions. This activation is due to the presence of the electron-donating alkyl group, which increases the electron density of the ring. The alkyl group donates electron density to the ring through inductive and resonance effects, making it more susceptible to electrophilic attack.

Explanation:

The correct answer is (A) Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1.

When benzene undergoes Friedel-Crafts alkylation, the first alkyl group substitutes one of the hydrogen atoms on the ring. This substitution introduces an electron-donating alkyl group onto the benzene ring, which activates the ring for further substitution reactions.

The presence of an alkyl group increases the electron density of the ring through inductive effects, where the alkyl group donates electron density through sigma bonds. Additionally, the alkyl group can also donate electron density to the ring through resonance effects, where the lone pair of electrons on the alkyl group can delocalize into the pi-system of the benzene ring.

The increased electron density of the ring makes it more nucleophilic and more susceptible to electrophilic attack. Therefore, after the introduction of one alkyl group, the benzene ring becomes activated for further substitution reactions. This activation allows for the possibility of polyalkylation, where multiple alkyl groups can substitute on the benzene ring.

In summary, Friedel-Crafts alkylation of benzene gives polyalkylated benzene, and the introduction of one alkyl group activates the ring for further substitution reactions.

Answer

Option A is correct.

When benzene reacts with ethyl chloride and AlCl3 as a catalyst we get ethyl benzene as the product. Here the first alkylated product is more nucleophilic than the starting benzene due to the presence of an electron donating group by which the ring gets activated for futher substitution and thus it undergoes alkylation which futher leads to poly alkylation.

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