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Friday, 9 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 topic in other shifts

All Alkenes and Alkynes questions
  1. 4 Apr 2026, Shift 1 · Q64An alkene (X) on ozonolysis followed by reduction gives following products. H−CHO\mathrm{H-CHO} (2 moles), OHC−CO−CHO\mathrm{OHC-CO-CHO}…HardDiagram basedHas a figure
  2. 4 Apr 2026, Shift 2 · Q64Compound (X) is subjected to the sequence of reactions as shown above. Molar mass of the major product (Y) formed is ________…MediumDiagram basedHas a figure
  3. 5 Apr 2026, Shift 1 · Q64"P" is a hydrocarbon of molecular formula:- C8H14\mathrm{C_8H_{14}}. On ozonolysis, "P" forms "Q". "Q" on treatment with alkali under reflux…HardDiagram basedHas a figure
  4. 6 Apr 2026, Shift 1 · Q66Given below are two statements: Statement I: 3-phenylpropene reacts with HBr and gives secondary alkyl bromide having a chiral carbon atom…MediumTwo statements
  5. 6 Apr 2026, Shift 2 · Q65An optically active alkyl bromide C4H9Br\mathrm{C_4H_9Br}, reacts with ethanolic KOH to form major compound [A] which reacts with bromine to…MediumSingle correct
  6. 2 Apr 2025, Shift 1 · Q66An optically active alkyl halide C4H9Br\mathrm{C_4H_9Br} [A] reacts with hot KOH dissolved in ethanol and forms alkene [B] as major product…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 42 of the 174 JEE Main shifts held from 2017 to 2026.