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Saturday, 31 October

JEE Main 2023 · ChemistryMultiple choiceDiagram basedHardConceptual

JEE Main 8 April 2023, Shift 1, Chemistry Q73

Question 73 of 90 in this shift, Chemistry question 13 of 30, Section A.

Choose the halogen which is most reactive towards SN1\mathrm{S_N1} reaction in the given compounds (A, B, C & D) A. [structure] B. [structure] C. [structure] D. [structure]

The figure, in words

Four skeletal structures, halogens labelled (a)/(b). A: phenyl-CH(Br(a))-CH(Br(b))-CH3. B: zigzag chain with a C=C in the middle, I(a) at one end and I(b) at the other end. C: bicyclo[2.2.1]heptane (norbornane) skeleton with Br(a) on a bridgehead carbon, and an adjacent carbon bearing both Br(b) and Me. D: branched (gem-dimethyl-type) quaternary carbon on the left of a zigzag chain with Br(a) on the carbon next to the branch point and Br(b) at the far end of the chain.
  1. (1)A−Br(a) ; B−I(a) ; C−Br(b) ; D−Br(a)\mathrm{A-Br_{(a)}\ ;\ B-I_{(a)}\ ;\ C-Br_{(b)}\ ;\ D-Br_{(a)}}Official answer
  2. (2)A−Br(a) ; B−I(a) ; C−Br(a) ; D−Br(a)\mathrm{A-Br_{(a)}\ ;\ B-I_{(a)}\ ;\ C-Br_{(a)}\ ;\ D-Br_{(a)}}
  3. (3)A−Br(b) ; B−I(a) ; C−Br(a) ; D−Br(a)\mathrm{A-Br_{(b)}\ ;\ B-I_{(a)}\ ;\ C-Br_{(a)}\ ;\ D-Br_{(a)}}
  4. (4)A−Br(b) ; B−I(b) ; C−Br(b) ; D−Br(b)\mathrm{A-Br_{(b)}\ ;\ B-I_{(b)}\ ;\ C-Br_{(b)}\ ;\ D-Br_{(b)}}

Official answer

Option 1

NTA final key.

Chapter
Haloalkanes and Haloarenes
Topic
SN1 and SN2 Mechanisms
Idea tested
SN1 Carbocation Intermediate

Same idea in other shifts

Asked 2× in all
  1. 3 Sep 2020, Shift 1 · Q44The mechanism of SN1\mathrm{S_N1} reaction is given as :…MediumOtherHas a figure

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.