Question

Consider the following sequence of reactions and identify \( A \), \( B \), and \( C \) respectively.

• A. \( \text{C}_6\text{H}_5\text{OH}, \, \text{C}_6\text{H}_6, \, \text{C}_6\text{H}_4\text{Br}_2 \)
• B. \( \text{C}_6\text{H}_5\text{N}_2^+, \, \text{C}_6\text{H}_6, \, \text{C}_6\text{H}_5\text{Br} \)
• C. \( \text{C}_6\text{H}_5\text{NO}_2, \, \text{C}_6\text{H}_6\text{OH}, \, \text{C}_6\text{H}_5\text{Br} \)
• D. \( \text{C}_6\text{H}_5\text{Cl}, \, \text{C}_6\text{H}_6\text{OH}, \, \text{C}_6\text{H}_5\text{Cl} \)

Hint:

When working with aromatic compounds, use the appropriate reagents to form diazonium salts and understand their subsequent reactions such as coupling and bromination.

Answer 1

The Correct Option is B

Step 1: Reaction with \( \text{NaNO}_2 \) and \( \text{HCl} \).
The reaction of an amine group with nitrous acid (\( \text{NaNO}_2 \)) in dilute HCl produces a diazonium salt. Hence, compound \( A \) will be \( \text{C}_6\text{H}_5\text{N}_2^+ \). Step 2: Reaction with \( \text{H}_3\text{PO}_4 \).
The diazonium salt undergoes further transformation to form benzene, so compound \( B \) will be \( \text{C}_6\text{H}_6 \). Step 3: Reaction with \( \text{Br}_2 \) and \( \text{FeBr}_3 \).
Bromination of benzene with \( \text{FeBr}_3 \) gives bromobenzene, so compound \( C \) will be \( \text{C}_6\text{H}_5\text{Br} \). Step 4: Conclusion.
Thus, the correct compounds are \( A = \text{C}_6\text{H}_5\text{N}_2^+ \), \( B = \text{C}_6\text{H}_6 \), and \( C = \text{C}_6\text{H}_5\text{Br} \). Final Answer: \[ \boxed{\text{C}_6\text{H}_5\text{N}_2^+, \, \text{C}_6\text{H}_6, \, \text{C}_6\text{H}_5\text{Br}} \]