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Question #43977
The Question
A chemist attempts to synthesize an azo dye starting from chlorobenzene via the following synthetic route:
Step 1: \ce{C6H5Cl} \textbf{P} (Major product)
Step 2: \textbf{P} \textbf{Q}
Step 3: \textbf{Q} \textbf{R}
Step 4: \textbf{R} \textbf{S} (after mild acidification)
Identify the final outcome (\textbf{S}) of this synthetic sequence.
Options
- A.
\ce{1-[(4-chlorophenyl)diazenyl]naphthalen-2-ol}
- B.
An unreacted mixture of \ce{4-chlorophenol} and \ce{naphthalen-2-ol}
- C.
\ce{4-[(2-hydroxynaphthalen-1-yl)diazenyl]phenol}
- D.
\ce{1-chloro-4-(naphthalen-2-yloxy)benzene}
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
DDT and Freon Chemistry|Azo Coupling Regioselectivity|Diazotization Temperature Sensitivity
Why This Question Is Tricky
Common Mistakes
This question tests the student's awareness of the strict thermal constraints of diazotization (Kinetic vs Thermodynamic stability of intermediates).
While mapping a synthetic route to an azo dye, students often mechanically apply the reagents without checking the temperature conditions.
By setting the diazotization temperature to 298 K instead of the required 273-278 K, the diazonium intermediate undergoes nucleophilic substitution with water (hydrolysis) to form a phenol.
This destroys the electrophile necessary for the subsequent electrophilic aromatic substitution (azo coupling), rendering the intended reaction impossible.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Haloalkanes and Haloarenes - Class 12 |
| Concept | DDT and Freon Chemistry |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |