Recognising how resonance contribtutes to the arrangement of charge around a ring helps to understand the reactivity of a substituted benzene.Consider the resonance contributors of the following compoundAccording to resonance, is the ring: activated or deactivated to electrophilic substitution. And which site/s are the most susceptible to substitution?

Question

BlackTom AI · Accepted Answer

The question asks us to assess how resonance affects the reactivity of the substituted benzene ring toward electrophilic substitution, specifically whether the ring is activated or deactivated and which positions (ortho, meta, para) are most susceptible.

Option a: 'Deactivated - meta sites are the most active.' This would imply the substituent withdraws electrons and directs electrophiles to the meta position. In many cases, strong electron-withdrawing groups deactivate the ring and favor meta substitution, but the given compound features a substituent capable of donating electron density via resonance (a nitrogen-containing group with lone pair delocalization). This makes activation and ortho/para directing more consistent with resonance donation, not deactivation. Therefore this option is unlikely.

Option b: 'Deactivated - ortho sites are the most active.' Here, deactivation is paired with ortho-directing. If the ring were deactivated, electrophilic substitution would be slow, and directing to ortho could occur with some electron-withdrawing groups like carbonyls, but the presence of a resonance-donating nitrogen substituent generally increases electron density and directs to ortho and para, not simply ortho. This combination (deactivation with ortho-directed) is not consistent with standard resonance effects of an electron-donating substituent.

Option c: 'Deactivated - ortho and para sites are the most active.' This says the ring is deactivated overall but still shows ortho/para preference. In typical cases, deactivation tends to reduce reactivity across the ring, and when deactivated, meta often becomes favored for some substituents. The coexistence of deactivation with ortho/para activation contradicts common directing rules for a resonance-donating substituent. This option is inconsistent with the expected directing outcome given the resonance contributors shown.

Option d: 'Activated - ortho and para sites are the most active.' This aligns with a substituent that donates electron density via resonance into the ring, increasing the overall reactivity (activation) and directing electrophilic attack to the ortho and para positions due to higher electron density at these positions from resonance structures. The resonance contributors shown (with lone-pair delocalization toward the ring and positive charge on the nitrogen in some forms) illustrate back-donation of electron density into the ring, supporting activation and ortho/para control.

Option e: 'Activated - meta sites are the most active.' Activation with meta directing would be unusual for an electron-donating substituent; meta activation is typically associated with electron-withdrawing groups that cannot donate electron density to the ortho/para positions but can stabilize positive charge at meta through certain resonance forms. Since the resonance forms in the diagram emphasize donation into the ring, this option contradicts the observed directing pattern. Therefore this choice is incorrect.

Overall, the reasoning for the provided resonance structures indicates electron donation into the ring, increasing reactivity (activation) and favoring ortho and para substitution, making option d the consistent choice with the resonance narrative.

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