Concept:The reactivity of an aromatic ring towards electrophiles is governed by the electron density of the ring. Groups that donate electrons into the ring activate it.
Formula:Not applicable to this conceptual question.
Solution:- The oxygen atom of the -OH group has lone pairs of electrons.
- Despite oxygen being more electronegative than carbon (which exerts an electron-withdrawing inductive effect, -I), the lone pairs heavily overlap with the \(\pi\)-system of the ring.
- This donates massive electron density via resonance, known as a strong positive mesomeric effect (+M).
- This +M effect vastly outweighs the -I effect, making the ring highly reactive.
Why other options are incorrect:Hydrogen bonding affects physical properties (boiling point, solubility) but not the internal ring electron density. The inductive effect of -OH is actually electron-withdrawing (-I), which would deactivate the ring if not for the overpowering mesomeric effect.
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