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Haloalkanes and Haloarenes question

2017 · 8 Apr · Shift 1 · Q5
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  5. /2017 · 8 Apr · Shift 1 · Q5

Haloalkanes and Haloarenes question

2017 · 8 Apr · Shift 1 · Q5

JEE MainChemistryHaloalkanes and HaloarenesMCQ+4 / −1
Which of the following compounds will not undergo Friedel Craft’s reaction with benzene ?
  1. A
    JEE Main 2017 (Online) 8th April Morning Slot Chemistry - Haloalkanes and Haloarenes Question 146 English Option 1
  2. B
    JEE Main 2017 (Online) 8th April Morning Slot Chemistry - Haloalkanes and Haloarenes Question 146 English Option 2
  3. C
    JEE Main 2017 (Online) 8th April Morning Slot Chemistry - Haloalkanes and Haloarenes Question 146 English Option 3
  4. D
    JEE Main 2017 (Online) 8th April Morning Slot Chemistry - Haloalkanes and Haloarenes Question 146 English Option 4
View written solutionFree

Correct answer: B

  1. Key idea of Friedel–Crafts reaction

    Friedel–Crafts alkylation/acylation of benzene requires formation of a suitable electrophile.

    • Alkyl halides react with a Lewis acid such as AlCl3\mathrm{AlCl_3}AlCl3​ to generate an alkyl electrophile.
    • Aryl halides and vinyl halides generally do not undergo Friedel–Crafts alkylation because they do not form the required carbocation/electrophilic species easily.
  2. Important exception/check

    In such questions, the compound that does not undergo Friedel–Crafts reaction is usually one where the halogen is attached to an:

    • sp2sp^2sp2 carbon of an alkene (vinyl halide), or
    • aromatic ring carbon (aryl halide).

    These fail because:

    • the C−X\mathrm{C-X}C−X bond has partial double bond character or is stronger,
    • formation of the corresponding cation is highly unstable.
  3. Using the stored answer

    Since the options are not visible in the prompt, I cannot independently inspect structures A,B,C,DA, B, C, DA,B,C,D. However, the stored correct answer is B, which indicates that option BBB is the compound that will not undergo Friedel–Crafts reaction with benzene.

  4. Conclusion

    Therefore, the answer is: B\boxed{B}B​

  5. Note

    If you provide the actual structures of options AAA to DDD, I can verify the mechanism explicitly for each one.

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