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Question #44630
The Question
An organic compound \textbf{X}, 1-(2-bromopropyl)-2,4-dimethoxybenzene, is treated with Potassium fluoride () and [2.2.2]cryptand in anhydrous benzene at .
Identify the major product \textbf{P}.
Options
- A.
(E)-1-(2,4-dimethoxyphenyl)prop-1-ene
- B.
5,7-dimethoxy-2-methyl-2,3-dihydro-1H-indene
- C.
1-(2-fluoropropyl)-2,4-dimethoxybenzene
- D.
3-(2,4-dimethoxyphenyl)prop-1-ene
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
E1/E2 Solvent and Base Effects|Electrophilic Substitution Activation/Deactivation
Why This Question Is Tricky
Common Mistakes
The question tests the 'Naked Base' exception in elimination reactions.
Students typically learn that fluoride is a weak base and poor nucleophile due to strong hydrogen bonding in protic solvents.
The hidden variable is the use of a cryptand in a non-polar solvent, which strips the solvent shell and counterion, transforming F- into a superbase.
This forces an E2 elimination.
The primary trap is the intramolecular EAS pathway (Option B); students see a highly activated aromatic ring and an alkyl halide, mistakenly assuming a spontaneous Friedel-Crafts alkylation without realizing a Lewis acid is strictly required to generate the electrophile.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Haloalkanes and Haloarenes - Class 12 |
| Concept | E1/E2 Solvent and Base Effects |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |