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Question #44927
The Question
Consider the reaction of \ce{1-(4-hydroxyphenyl)-4,4,4-trifluorobutane-1,3-dione} with one equivalent of benzenediazonium chloride (\ce{PhN2+ Cl-}) in an aqueous buffer at and . Identify the major product formed.
Options
- A.
\ce{1-(4-hydroxyphenyl)-4,4,4-trifluoro-2-(2-phenylhydrazono)butane-1,3-dione}
- B.
\ce{1-(4-hydroxy-3-(phenyldiazenyl)phenyl)-4,4,4-trifluorobutane-1,3-dione}
- C.
\ce{1-(4-hydroxyphenyl)-2-(2-phenylhydrazono)ethan-1-one}
- D.
\ce{4,4,4-trifluoro-1-(4-(phenyldiazenyloxy)phenyl)butane-1,3-dione}
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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
Azo Coupling Regioselectivity|Enolate Regioselectivity|Inductive Effect Trends
Why This Question Is Tricky
Common Mistakes
This question tests the student's ability to evaluate competing nucleophilic sites in a multifunctional molecule.
The core trap is the conditioned reflex to associate azo coupling exclusively with activated aromatic rings (phenols/anilines).
Students often ignore the active methylene or assume the phenol is more reactive.
The hidden variable is the profound inductive effect of the group, which lowers the of the active methylene, ensuring a high concentration of the kinetic enolate.
Furthermore, the carbonyl group deactivates the aromatic ring, shifting the regioselectivity entirely to the aliphatic chain.
Distractor C traps students who over-apply the Japp-Klingemann reaction, forgetting that cleavage only occurs when tautomerization to the hydrazone is impossible.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Amines - Class 12 |
| Concept | Azo Coupling Regioselectivity |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |