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Saturday, 31 October

JEE Main 2022 · ChemistryMultiple choiceDiagram basedMediumConceptual

JEE Main 29 June 2022, Shift 2, Chemistry Q73

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

Which of the following carbocations is most stable?

The figure, in words

Four line-drawn carbocations with methoxy groups, one per option.
  1. (1)[figure: line structure; a double bond to a carbon bearing an OCH3 group, and a single bond from that carbon to a carbon carrying a positive charge (circled plus)]
  2. (2)[figure: line structure; a terminal double bond to a carbon bearing an OCH3 group (drawn upward), then a single bond, then a C=C double bond, then a single bond to the end carbon carrying a positive charge (circled plus)]
  3. (3)[figure: line structure; H3CO attached to a carbon, then a C=C double bond, ending in a carbon carrying a positive charge (circled plus)]
  4. (4)[figure: line structure; H3CO attached to a zigzag chain with two C=C double bonds, ending in a carbon carrying a positive charge (circled plus)]Official answer

Official answer

Option 4

NTA final key.

Chapter
Organic Chemistry: Some Basic Principles and Techniques
Topic
Resonance and Hyperconjugation
Idea tested
Relative Stability

Same idea in other shifts

Asked 4× in all
  1. 9 Apr 2024, Shift 1 · Q71Relative stability of the contributing structures is : (I) CH2=CH−C∥O¨:−H\mathrm{CH_2=CH-\overset{\ddot{O}:}{\overset{\|}{C}}-H} ⟷\longleftrightarrow…MediumSingle correctHas a figure
  2. 9 Apr 2024, Shift 2 · Q73The correct stability order of the following resonance structures of CH3−CH=CH−CHO\mathrm{CH_3-CH=CH-CHO} is I:…MediumSingle correctHas a figure
  3. 29 Jan 2024, Shift 1 · Q73The difference in energy between the actual structure and the lowest energy resonance structure for the given compound isEasySingle correct

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.