MCQ Detailed View

When phenol (C₆H₅OH) is heated strongly with zinc metal, a reduction reaction takes place. Zinc acts as a reducing agent and removes the hydroxyl group (–OH) from phenol in the form of zinc oxide (ZnO). The aromatic ring remains intact, and the final product formed is benzene (C₆H₆). The reaction can be represented as:

C₆H₅OH + Zn → C₆H₆ + ZnO

This reaction is a classic laboratory method for converting phenol back into benzene. It demonstrates the strong reducing property of zinc, which facilitates the removal of oxygen atoms from organic molecules.

Let us analyze the options:

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  Benzene is the correct product because the –OH group is completely removed, restoring the simple aromatic hydrocarbon.

  
  


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  Toluene (C₆H₅CH₃) is incorrect because no methyl group is added in this reaction.

  
  


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  Cyclohexane (C₆H₁₂) is also incorrect since the aromaticity is not lost; only the –OH group is removed.

  
  


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  Aniline (C₆H₅NH₂) is not possible because no amination occurs with zinc.

  
  

The importance of this reaction lies in its application in organic synthesis and understanding phenol reactivity. Phenol is more reactive than benzene due to the electron-donating effect of the –OH group, but when reduced, it gives back the parent aromatic hydrocarbon. This reaction is also an excellent demonstration of aromatic stability, as the system tends to revert to benzene, a highly stable aromatic molecule.

In industry and labs, this method is sometimes used when benzene is required from phenolic compounds. It also serves as an experimental proof that the hydroxyl group in phenol is directly attached to the aromatic ring, since its removal regenerates benzene.

Hence, heating phenol with zinc produces benzene as the major product.