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Saturday, 31 October

JEE Main 2020 · ChemistryMultiple choiceDiagram basedHardApplication

JEE Main 2 September 2020, Shift 1, Chemistry Q41

Question 41 of 75 in this shift, Chemistry question 16 of 25.

The major product in the following reaction is : 1-methyl-1-vinylcyclopentane (H3C\mathrm{H_3C} and CH=CH2\mathrm{CH=CH_2} on the same ring carbon of cyclopentane) →HeatH3O+\xrightarrow[\text{Heat}]{\mathrm{H_3O^+}}

The figure, in words

Reactant: cyclopentane ring with a quaternary carbon bearing H3C and CH=CH2; reagent H3O+, Heat. Options are skeletal structures.
  1. (1)[figure: 1,2-dimethylcyclohexene, cyclohexene ring with double bond between two carbons each bearing a CH3]Official answer
  2. (2)[figure: 3,3-dimethylcyclohexene, cyclohexene ring with gem-dimethyl carbon next to the double bond]
  3. (3)[figure: 1-(1-methylcyclopentyl)ethanol, cyclopentane with CH3 and CH(OH)CH3 on the same ring carbon]
  4. (4)[figure: 1-isopropylcyclopentene, cyclopentene ring with CH(CH3)2 on a double-bond carbon]

Official answer

Option 1

NTA final key (Sep 2020).

Chapter
Hydrocarbons
Topic
Alkenes and Alkynes
Idea tested
Carbocation Rearrangements

Same idea in other shifts

Asked 5× in all
  1. 6 Apr 2023, Shift 2 · Q75In the following reaction, 'B' isHardDiagram basedHas a figure
  2. 24 Feb 2021, Shift 1 · Q41What is the major product formed by HI on reaction with [figure] ?MediumDiagram basedHas a figure
  3. 24 Feb 2021, Shift 1 · Q44What is the final product (major) ‘A’ in the given reaction ? [figure] →HCl\xrightarrow{\mathrm{HCl}} ‘A’ (major product)MediumDiagram basedHas a figure
  4. 17 Mar 2021, Shift 1 · Q43[reaction drawn: see figure_note] Product “A” in the above chemical reaction is :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.