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JEE Main 2026 Jan 21 Shift 2, Chemistry Q9: Properties of Alkyl Halides (Halo Alkanes) & Aryl Halides (Halo Arenes)

JEE Main2026Jan 21, Shift 2Chemistry
Q.

The correct order of reactivity of the following benzyl halides towards reaction with KCN is:

  1. A

    a > b > c > d

  2. B

    b > a > d > c

  3. C

    b > a > c > d

  4. D

    a > b > d > d

Solution

This is an -type process where rate stability of the benzyl carbocation intermediate.

Electron-donating groups at para stabilise the cation via resonance: is a stronger -donor than , so (b) > (a).

Electron-withdrawing destabilises the cation. At the para position, withdraws through both resonance and induction directly into the carbocation centre. At meta, only the inductive effect is felt (no direct resonance into the benzyl cation). So m- destabilises less than p-, giving (d) > (c).

Overall: b > a > d > c.

Concept behind this question

Properties of Alkyl Halides (Halo Alkanes) & Aryl Halides (Halo Arenes)Notes, formulas and examples →

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