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Question #44038

Difficulty: 8/10 | 🟢 Free

The Question

An organic compound \textbf{X} (4-methylbenzamide) is treated with \ce{Br2 (l)} and \ce{NaOH (aq)} to form intermediate \textbf{Y}. Due to improper thermal regulation during the highly exothermic neutralization and subsequent addition of \ce{NaNO2 (aq)} and \ce{HCl (aq)}, the reaction mixture temperature reaches $40^\circ\text{C}$ , yielding product \textbf{Z}. Finally, \textbf{Z} is treated with a freshly prepared solution of 4-nitrobenzenediazonium chloride \ce{(aq)} in an aqueous buffer of pH 9.5 to form the major product \textbf{W}. Identify the structure of \textbf{W}.

Options

A.
4-methyl-2-[(4-nitrophenyl)diazenyl]phenol
B.
No reaction occurs in the final step
C.
4-methyl-3-[(4-nitrophenyl)diazenyl]phenol
D.
4-methyl-2-[(4-nitrophenyl)diazenyl]aniline

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.

Concepts Behind This Question

Hoffmann Bromamide Rearrangement|Diazotization Temperature Sensitivity|Azo Coupling Regioselectivity

Why This Question Is Tricky

Common Mistakes

This problem tests the student's awareness of the strict thermal constraints of diazotization and regioselectivity in azo coupling.

Students often blindly follow the Amide -> Amine -> Diazonium sequence without noting the $40^\circ\text{C}$ condition.

The hidden variable is the thermal decomposition of the diazonium salt into a phenol.

If missed, students will falsely assume \textbf{Z} is a diazonium salt and conclude that the final coupling step fails (Option B).

Furthermore, it tests regioselectivity: recognizing that since the para position of $p$ -cresol is blocked, coupling must occur at the ortho position dictated by the dominant activating group (-OH).

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Amines - Class 12
Concept	Hoffmann Bromamide Rearrangement
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free