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Saturday, 31 October

JEE Main 2021 · ChemistryMultiple choiceDiagram basedMediumDiagram reading

JEE Main 3 August 2021, Shift 1, Chemistry Q50

Question 50 of 90 in this shift, Chemistry question 20 of 30, Section A.

Which of the following is the most stable conformer?

The figure, in words

Four Newman projections (circle with three lines meeting at the centre), described per option.
  1. (1)[figure: Newman projection; substituents drawn: H at top, OH at upper right, H at left, H at right, H at lower left, OH at lower right]
  2. (2)[figure: Newman projection; substituents drawn: OH at top, H at upper left, H at upper right, H at lower left, H at lower right, OH at bottom]
  3. (3)[figure: Newman projection; substituents drawn: OH at top, H at upper left, OH at upper right, H at lower left, H at lower right, H at bottom]Official answer
  4. (4)[figure: Newman projection; substituents drawn: OH at top, OH at upper right directly next to it, H at left, H at lower left, H at right, H at bottom]

Official answer

Option 3

NTA final key.

Chapter
Organic Chemistry: Some Basic Principles and Techniques
Topic
Alkanes and Free Radicals
Idea tested
Ethane and Butane Conformers

Same idea in other shifts

Asked 3× in all
  1. 25 Jun 2022, Shift 1 · Q72In the following structures, which one is having staggered conformation with maximum dihedral angle ?EasyDiagram basedHas a figure
  2. 31 Aug 2021, Shift 2 · Q42Arrange the following conformational isomers of n-butane in order of their increasing potential energy : [four Newman projections labelled…MediumDiagram 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.