Learn

Saturday, 31 October

JEE Main 2020 · ChemistryMultiple choiceOtherMediumConceptual

JEE Main 3 September 2020, Shift 1, Chemistry Q44

Question 44 of 75 in this shift, Chemistry question 19 of 25.

The mechanism of SN1\mathrm{S_N1} reaction is given as : R−X⟶R⊕X⊖⟶R⊕ ∥ X⊖→Y⊖R−Y+X⊖\mathrm{R-X\longrightarrow R^{\oplus}X^{\ominus}\longrightarrow R^{\oplus}\,\|\,X^{\ominus}\xrightarrow{Y^{\ominus}}R-Y+X^{\ominus}} Ion pair; Solvent Separated ion pair A student writes general characteristics based on the given mechanism as : (a) The reaction is favoured by weak nucleophiles. (b) R⊕\mathrm{R^{\oplus}} would be easily formed if the substituents are bulky. (c) The reaction is accompanied by racemization. (d) The reaction is favoured by non-polar solvents. Which observations are correct ?

The figure, in words

Reaction scheme printed in the stem: R-X, then an arrow to R(+) X(-) labelled "Ion pair", then an arrow to R(+) || X(-) labelled "Solvent Separated ion pair" (the word Solvent sits over the || ), then an arrow with Y(-) above it to R-Y + X(-).
  1. (1)(a) and (b)
  2. (2)(b) and (d)
  3. (3)(a), (b) and (c)Official answer
  4. (4)(a) and (c)

Official answer

Option 3

NTA final key (Sep 2020).

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

Same idea in other shifts

Asked 2× in all
  1. 8 Apr 2023, Shift 1 · Q73Choose the halogen which is most reactive towards SN1\mathrm{S_N1} reaction in the given compounds (A, B, C & D) A. [structure] B.…HardDiagram basedHas 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.