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Question #44943
The Question
Consider the following two-step reaction sequence:
Step 1: 2,6-Dimethylaniline is treated with excess \ce{CH3I} to form a quaternary salt, which is subsequently reacted with moist \ce{Ag2O} and heated to yield compound \textbf{X} as the major aromatic product.
Step 2: Compound \textbf{X} is treated with benzenediazonium chloride (\ce{PhN2+Cl-}) in a weakly acidic buffer (pH 4-5) at to yield product \textbf{Y}.
Identify the outcome of Step 2 (Product \textbf{Y}).
Options
- A.
4-(Phenyldiazenyl)-2,6-dimethyl-N,N-dimethylaniline
- B.
3-(Phenyldiazenyl)-2,6-dimethyl-N,N-dimethylaniline
- C.
No reaction occurs; 2,6-dimethyl-N,N-dimethylaniline is recovered
- D.
4-(Phenyldiazenyl)-2,6-dimethylaniline
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
Coupling Reactivity|Ortho-Effect in Anilines|Azo Coupling Regioselectivity
Why This Question Is Tricky
Common Mistakes
This question tests the 'Steric Inhibition of Resonance' (SIR) exception in electrophilic aromatic substitution.
Students typically apply the heuristic that aniline derivatives universally undergo para-azo coupling due to high electron density.
The trap lies in the structural synthesis of Compound X (2,6-dimethyl-N,N-dimethylaniline).
The bulky tertiary amine group, flanked by ortho-methyls, is forced out of planarity.
This hidden variable shuts down the +M mesomeric effect, leaving the ring insufficiently nucleophilic to react with the weak diazonium electrophile, thereby rendering the expected coupling kinetically impossible.
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 |