Which of the following is/are more reactive towards...

Which of the following is/are more reactive towards nitration than benzene? (a) $\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CH}_{3} / \mathrm{HF}$ (b) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Cl} /$ Anh. $\mathrm{AlCl}_{3}$ (c) $\mathrm{CH}_{3}-\mathrm{CHCH}_{3} / \mathrm{Anh} . \mathrm{AlCl}_{3}$ (d) All of these

Which of the following is/are more reactive towards nitration than benzene?
(a) $\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CH}_{3} / \mathrm{HF}$
(b) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Cl} /$ Anh. $\mathrm{AlCl}_{3}$
(c) $\mathrm{CH}_{3}-\mathrm{CHCH}_{3} / \mathrm{Anh} . \mathrm{AlCl}_{3}$
(d) All of these

Key Concepts

Activating and Deactivating Substituents

In aromatic electrophilic substitution, substituents attached to the benzene ring can either increase (activate) or decrease (deactivate) its reactivity towards the electrophilic attack. Activating groups, such as alkyl groups, donate electron density through inductive effects or hyperconjugation, making the ring more reactive than benzene. Understanding how different groups influence reactivity is key in predicting and comparing the outcomes of aromatic substitution reactions.

Electrophilic Aromatic Substitution (EAS)

This concept refers to a fundamental reaction mechanism in aromatic chemistry in which an electrophile replaces a hydrogen atom on an aromatic ring. The process involves the formation of a resonance?stabilized arenium ion intermediate, and the overall reactivity is largely determined by the stability of this intermediate. Nitration, where a nitro group is introduced into the aromatic ring, is one of the quintessential examples of EAS.

Carbocation Formation and Stability in Friedel–Crafts Reactions

Many electrophilic aromatic substitutions, such as Friedel–Crafts alkylation, proceed via the formation of carbocations from alkyl halides in the presence of a Lewis acid catalyst (for example, AlCl3). The stability of the resulting carbocation, which may be primary, secondary, or even allylic in nature, plays a crucial role in determining the rate and the orientation of the aromatic substitution. More stable carbocations (often through rearrangement or resonance stabilization) lead to a higher reactivity compared to benzene that lacks such activating intermediates.

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