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Saturday, 31 October

JEE Main 2024 · ChemistryMultiple choiceDiagram basedEasyApplication

JEE Main 5 April 2024, Shift 2, Chemistry Q77

Question 77 of 90 in this shift, Chemistry question 17 of 30, Section A.

Identify the major product in the following reaction. 1-bromo-1-methylcyclopentane →C2H5OHOˉH\xrightarrow[\mathrm{C_2H_5OH}]{\bar{\mathrm{O}}\mathrm{H}} Major Product

The figure, in words

Reactant: cyclopentane ring with Br and CH3\mathrm{CH_3} on the same ring carbon; reagent OˉH\bar{\mathrm{O}}\mathrm{H} in C2H5OH\mathrm{C_2H_5OH} over arrow.
  1. (1)methylenecyclopentane (cyclopentane ring with exocyclic =CH2=\mathrm{CH_2})
  2. (2)1-methylcyclopentene (ring double bond, CH3\mathrm{CH_3} on the alkene carbon)Official answer
  3. (3)1-bromocyclopentene (ring double bond, Br on the alkene carbon)
  4. (4)methylcyclopentane

Official answer

Option 2

NTA final key.

Chapter
Haloalkanes and Haloarenes
Topic
Alkenes and Alkynes
Idea tested
Saytzeff vs. Hofmann Elimination

Same idea in other shifts

Asked 7× in all
  1. 2 Apr 2025, Shift 2 · Q75Consider the above sequence of reactions. 151 g of 2-bromopentane is made to react. Yield of major product P is 80% whereas Q is 100%.…MediumNumerical valueHas a figure
  2. 25 Jun 2022, Shift 1 · Q75The major product in the reaction [figure: CH3−C(CH3)(CH3)−Cl\mathrm{CH_3-C(CH_3)(CH_3)-Cl} (central C with CH3\mathrm{CH_3} above, CH3\mathrm{CH_3} below,…EasySingle correctHas a figure
  3. 31 Aug 2021, Shift 2 · Q41The major product of the following reaction is : [reaction: starting material drawn as a five-membered ring; reagent above/below arrow:…MediumDiagram basedHas a figure
  4. 2 Sep 2020, Shift 2 · Q44The major product obtained from E2\mathrm{E_2}-elimination of 3-bromo-2-fluoropentane is :HardSingle correctHas a figure
  5. 2 Apr 2017 (offline) · Q52Which of the following, upon treatment with *tert*-BuONa followed by addition of bromine water, fails to decolourize the colour of bromine ?HardSingle correctHas a figure
  6. 2 Apr 2017 (offline) · Q56The major product obtained in the following reaction is : [reaction: (+)-C6H5CH(Br)CH2C6H5\mathrm{C_6H_5CH(Br)CH_2C_6H_5} (Br on wedge, H on hash at the…MediumSingle correctHas 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.