Concept:The stability of a conjugate base determines the acidity of the parent compound. Resonance delocalization significantly enhances stability.
Formula:Not applicable to this conceptual question.
Solution:- In the phenoxide ion (\(\text{C}_6\text{H}_5\text{O}^-\)), the negative charge resides on the oxygen atom.
- One of the lone pairs on the oxygen atom resides in a p-orbital that is perfectly parallel to the \(\pi\)-system of the aromatic ring, allowing the negative charge to be delocalized over the ortho and para carbon atoms of the ring.
- This dispersion of charge heavily stabilizes the phenoxide ion relative to the ethoxide ion, where the charge is completely localized on the oxygen.
Why other options are incorrect:Option C is factually wrong (the charge is delocalized, not localized). Option D is wrong because ethoxide has no \(\pi\)-system for delocalization. Option B is a structural fact but doesn't explain the
mechanism of stability like resonance (Option A) does.
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