Phenol Acidity

Question

Phenol is a stronger acid than cyclohexanol because:

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1. **Acidity Logic**: The acidity of a compound depends on the stability of its conjugate base (the anion formed after losing $H^+$).
2. **Cyclohexanol**: Its conjugate base, the cyclohexoxide ion, is an alkoxide. The negative charge is localized on the Oxygen atom. There is also an $+I$ effect from the ring, which destabilizes the charge.
3. **Phenol**: Its conjugate base is the **phenoxide ion** ($C_6H_5O^-$).
4. **Resonance Stabilization**: The negative charge on the Oxygen is in conjugation with the aromatic $\pi$-system. It is delocalized over the ortho and para positions of the benzene ring.
5. **Conclusion**: Because the phenoxide ion is **resonance stabilized**, the equilibrium favors the loss of a proton more than in cyclohexanol, making phenol a significantly stronger acid.

Phenol Acidity

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