Question

What is the major product 'Z' in the given reaction sequence?

• A. Benzene
• B. Phenol
• C. p-benzoquinone
• D. Chlorophenol

Hint:

Diazonium salts are extremely versatile intermediates in aromatic chemistry. Key replacement reactions to remember:
- with H\(_3\)PO\(_2\) or CH\(_3\)CH\(_2\)OH: Replaced by -H (deamination).
- with H\(_2\)O/warm: Replaced by -OH (forms phenol).
- with CuCl/HCl (Sandmeyer): Replaced by -Cl.
- with KI: Replaced by -I.

Answer 1

The Correct Option is A

To determine the major product 'Z' in the given reaction sequence, we need to analyze each step carefully.

1. Start with the nitrobenzene (\(\text{C}_6\text{H}_5\text{NO}_2\)) and react it with Fe/HCl. This step reduces the nitro group to an amino group. Hence, the product 'X' is aniline (\(\text{C}_6\text{H}_5\text{NH}_2\)).
2. The next reaction involves treating aniline with NaNO₂ and HCl at 273 K, which leads to the formation of a diazonium salt. Thus, 'Y' is benzene diazonium chloride (\(\text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^-\)).
3. Finally, when benzene diazonium chloride is treated with hypophosphorous acid (H₃PO₂) and water, it undergoes a reduction to form benzene (\(\text{C}_6\text{H}_6\)). Therefore, the major product 'Z' is benzene.

Thus, the correct answer to the question is: 

Benzene

This sequence of reactions is an example of the utilization of diazonium chemistry in the conversion of nitrobenzene to benzene.