Question

In the following reaction, condition 'A' is -

• A. Reduction with Zinc dust
• B. Dehydration with \(\text{H}_2\text{SO}_4\) / 443 K
• C. Treatment with \(\text{CS}_2\) / low temperture
• D. Oxidation with \(\text{CrO}_3\)

Hint:

Phenol is oxidised to p-benzoquinone by chromic acid.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
The figure shows phenol, a benzene ring with one OH, turning into a ring with two C=O groups on opposite carbons. This product is p-benzoquinone, so the change is an oxidation.

Step 2: Check the options
(A) Reduction with zinc dust removes the OH and gives benzene. It does not add oxygen.
(B) Dehydration with \(\text{H}_2\text{SO}_4\) at 443 K is used to turn alcohols into alkenes, not for phenols.
(C) Treatment with \(\text{CS}_2\) at low temperature is used for bromination in a non-polar solvent to give mono-bromophenols.
(D) Oxidation with \(\text{CrO}_3\) (chromic acid) converts phenol into p-benzoquinone, a conjugated cyclic diketone. Correct.

Final Answer:
Phenol is oxidised by chromic acid to p-benzoquinone, option (D). \[ \boxed{\text{Oxidation with CrO}_3} \]