Concept:The rate of electrophilic aromatic substitution (like sulfonation) depends on the electron density of the aromatic ring. Electron-donating groups activate the ring (making it react faster), while electron-withdrawing groups deactivate it.
Solution:- Benzene: The baseline standard.
- Nitrobenzene: The \( -\text{NO}_2 \) group is highly electronegative and strongly withdraws electrons via resonance, heavily deactivating the ring.
- Chlorobenzene: Halogens withdraw electrons inductively, making the ring mildly deactivated compared to benzene.
- Toluene (Methylbenzene): The methyl group (\( -\text{CH}_3 \)) pushes electron density into the ring through inductive effects and hyperconjugation. This makes the ring significantly more electron-rich and thus most reactive/readily sulphonated among the choices.
Why other options are incorrect:- Benzene lacks the activating methyl group.
- Chlorobenzene and Nitrobenzene are deactivated and react much slower than pure benzene.
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