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Saturday, 31 October

JEE Main 2021 · ChemistryMultiple choiceDiagram basedMediumDiagram reading

JEE Main 25 July 2021, Shift 1, Chemistry Q41

Question 41 of 90 in this shift, Chemistry question 11 of 30, Section A.

Which one among the following resonating structures is not correct ?

The figure, in words

Four resonance structures of a nitro-substituted conjugated diene system, differing in charge placement.
  1. (1)[figure: structure CH2=CH-CH(-)-CH(+)-N(+)(=O)O(-), i.e. vinyl group, carbanion carbon, adjacent carbocation carbon bearing the nitro group]Official answer
  2. (2)[figure: structure CH2=CH-CH(+)-CH(-)-N(+)(=O)O(-), i.e. vinyl group, carbocation carbon, adjacent carbanion carbon bearing the nitro group]
  3. (3)[figure: structure (+)CH2-CH(-)-CH=CH-N(+)(=O)O(-)... drawn as +, then carbon bearing -, then CH=CH attached to N(+)(=O)O(-)]
  4. (4)[figure: structure (+)CH2-CH=CH-CH=N(+)(O(-))O(-), i.e. extended conjugated chain ending in N with two O(-) and a positive charge on N]

Official answer

Option 1

NTA final key.

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

Same idea in other shifts

Asked 3× in all
  1. 22 Jul 2021, Shift 2 · Q43Which one of the following compounds does not exhibit resonance ?MediumSingle correctHas a figure
  2. 25 Jul 2021, Shift 2 · Q38Identify the species having one π\pi-bond and maximum number of canonical forms from the following :MediumSingle 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.