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Question #45097
The Question
Consider the reaction of 1-(3,5-difluoro-2-nitrophenyl)ethan-1-one with 1.0 equivalent of \ce{NaOCH3} in \ce{CH3OH} at 298 K. After 1 hour, the reaction mixture is carefully neutralized with dilute aqueous \ce{HCl}. Identify the major organic product isolated.
Options
- A.
1-(3-fluoro-5-methoxy-2-nitrophenyl)ethan-1-one
- B.
1-(5-fluoro-3-methoxy-2-nitrophenyl)ethan-1-one
- C.
1-(3,5-dimethoxy-2-nitrophenyl)ethan-1-one
- D.
1-(3,5-difluoro-2-nitrophenyl)ethan-1-one
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
Tautomerism Conditions|Nucleophilic Aromatic Substitution (SNAr)|Reaction Intermediates Stability
Why This Question Is Tricky
Common Mistakes
This problem tests the competition between acid-base chemistry (enolization) and Nucleophilic Aromatic Substitution (SNAr).
Students typically focus on the electronic effects of the nitro group activating the ring for SNAr, predicting substitution at the less sterically hindered para position (Option A).
However, they overlook the 'Hidden Variable': the enhanced acidity of the alpha-protons due to the ortho-nitro group's ability to stabilize the enolate via intramolecular interactions.
The rapid formation of the enolate anion electrostatically deactivates the ring, halting SNAr under these mild conditions.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Organic Chemistry – Some Basic Principles and Techniques - Class 11 Part 2 |
| Concept | Tautomerism Conditions |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |