Concept:Phenol contains a tough \(\text{C}-\text{O}\) bond with partial double-bond character. Removing this oxygen (deoxygenation) to yield benzene requires a strong, specific reducing agent and heat.
Formula:$$ \text{C}_6\text{H}_5\text{OH} + \text{Zn (dust)} \xrightarrow{\Delta} \text{C}_6\text{H}_6 + \text{ZnO} $$
Solution:- When phenol vapors are passed over heated zinc dust, a redox reaction occurs.
- Zinc acts as a reducing agent, abstracting the oxygen atom to form solid zinc oxide (ZnO).
- The remaining hydrogen bonds to the phenyl radical, regenerating the aromatic ring to form pure benzene.
- This is definitively a reduction with zinc.
Why other options are incorrect:Reduction with \(\text{H}_2\)/Ni yields cyclohexanol (it reduces the double bonds in the ring, not the C-O bond). Alkalies form sodium phenoxide. Standard acids do not reduce phenol.
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