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Friday, 16 October

JEE Main 2020 · ChemistryMultiple choiceDiagram basedHardMulti-step

JEE Main 8 January 2020, Shift 1, Chemistry Q43

Question 43 of 75 in this shift, Chemistry question 18 of 25, Section A.

The major products A and B in the following reactions are : (CH3)2CH−CH(CH3)−CN(\mathrm{CH_3})_2\mathrm{CH{-}CH(CH_3){-}CN} →HeatPeroxide\xrightarrow[\text{Heat}]{\text{Peroxide}} [A] [A] + (an unbranched zigzag terminal alkene) ⟶\longrightarrow B

The figure, in words

Skeletal structures. Substrate: isopropyl-CH(CH3)-CN. Alkene is an unbranched terminal alkene. Options give radical A (dot position differs) and product B skeletal structures; B drawings approximate.
  1. (1)[figure: A = radical on the carbon bearing CN (alpha to CN); B = skeletal structure with CN on a quaternary carbon carrying an isopropyl-type branch and a short ethyl-type chain]
  2. (2)[figure: A = radical on the isopropyl carbon, (CH3)2C˙−CH(CH3)−CN(CH_3)_2\dot{C}-CH(CH_3)-CN; B = zigzag chain joined to a carbon bearing methyl branches, followed by CH(CH3)-CN]
  3. (3)[figure: A = radical on the carbon bearing CN, (CH3)2CH−C˙(CH3)−CN(CH_3)_2CH-\dot{C}(CH_3)-CN; B = unbranched zigzag chain joined to a quaternary carbon bearing CN, methyl and isopropyl groups]Official answer
  4. (4)[figure: A = radical on the isopropyl carbon, (CH3)2C˙−CH(CH3)−CN(CH_3)_2\dot{C}-CH(CH_3)-CN; B = long zigzag chain joined to a quaternary carbon bearing two methyls, adjacent to CH(CH3)-CN]

Official answer

Option 3

NTA final key (Jan 2020).

Chapter
Hydrocarbons
Topic
No close match in our taxonomy
Idea tested
No close match in our taxonomy

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 42 of the 174 JEE Main shifts held from 2017 to 2026.