Question

What is the major product formed when phenol is treated with sodium dichromate (\( \text{Na}_2\text{Cr}_2\text{O}_7 \)) and sulfuric acid (\( \text{H}_2\text{SO}_4 \))?

• A. Benzoic acid
• B. Benzaldehyde
• C. 2-Nitrophenol
• D. p-Benzoquinone

Hint:

Phenol reacts with strong oxidizing agents like dichromate in acid to form quinones, particularly p-benzoquinone via intermediate formation of hydroquinone.

Answer 1

The Correct Option is D

Step 1: Identify the starting compound.
The given compound is phenol (\( \text{C}_6\text{H}_5\text{OH} \)). Step 2: Understand the reagents.
\(\text{Na}_2\text{Cr}_2\text{O}_7\) in acidic medium is a strong oxidizing agent. It oxidizes phenol to p-benzoquinone. Step 3: Reaction mechanism overview.
Phenol undergoes oxidation first to form hydroquinone (1,4-dihydroxybenzene), which is then further oxidized to p-benzoquinone. \[ \text{Phenol} \xrightarrow[\text{H}_2\text{SO}_4]{\text{Na}_2\text{Cr}_2\text{O}_7} \text{p-Benzoquinone} \]