Before You Begin
Question #44944
The Question
An aqueous solution of 4-methylbenzenediazonium chloride () is prepared at in dilute . The thermal decomposition of this diazonium salt to 4-methylphenol and proceeds via an mechanism. The first-order rate constant for this decomposition is at .
During a synthesis protocol, the cooling bath fails, and the acidic reaction mixture is inadvertently exposed to for exactly 20 minutes. The mixture is then rapidly quenched to , and an excess of alkaline naphthalen-2-ol (-naphthol) is immediately added to achieve complete electrophilic aromatic substitution.
Assuming no volume change and quantitative coupling of the surviving diazonium ions, identify the major organic products in the final mixture (excluding unreacted naphthalen-2-ol) and their exact molar ratio. (Given: )
Options
- A.
1-(p-tolylazo)naphthalen-2-ol and 4-methylphenol in a molar ratio
- B.
1-(p-tolylazo)naphthalen-2-ol and 4-methylphenol in a molar ratio
- C.
4-(p-tolylazo)naphthalen-2-ol and 4-methylphenol in a molar ratio
- D.
1-(p-tolylazo)naphthalen-2-ol and 4-methylphenol in a molar ratio
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Exception_Exposure
Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.
Concepts Behind This Question
Coupling Reactivity|Diazotization Temperature Sensitivity|Sandmeyer vs Gattermann
Why This Question Is Tricky
Common Mistakes
This question tests the thermodynamic and kinetic instability of diazonium salts, a frequently overlooked concept.
Students often assume diazonium salts are indefinitely stable and ready for coupling regardless of temperature.
The trap introduces a thermal threshold conflict: at , the diazonium salt undergoes competitive decomposition to a phenol faster than it can be preserved.
The problem requires integrating first-order chemical kinetics with organic synthesis, recognizing that coupling with the formed phenol is suppressed in acidic media, and correctly identifying the C-1 regioselectivity of -naphthol coupling.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Amines - Class 12 |
| Concept | Coupling Reactivity |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |