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Friday, 9 October

JEE Main 2025 · ChemistryMultiple choiceSingle correctMediumConceptual

JEE Main 2 April 2025, Shift 1, Chemistry Q64

Question 64 of 75 in this shift, Chemistry question 14 of 25, Section A.

Consider the following compound (X) H−C≡C−CH2−CH(CH3)−CH3\mathrm{H-C{\equiv}C-CH_2-CH(CH_3)-CH_3} with the carbons numbered I (the terminal ≡\equivC-H carbon), II (CH2\mathrm{CH_2}), III (the CH bearing the CH3\mathrm{CH_3} branch) and IV (the terminal CH3\mathrm{CH_3}). The most stable and least stable carbon radicals, respectively, produced by homolytic cleavage of corresponding C−-H bond are :

The figure, in words

Structural formula of compound (X): H-C≡C-CH2-CH(CH3)-CH3, i.e. H-C(I)≡C-CH2(II)-CH(III)-CH3(IV) with a CH3 substituent hanging below the CH(III) carbon. Labels I, II, III, IV are written above the carbons.
  1. (1)II, IOfficial answer
  2. (2)III, II
  3. (3)II, IV
  4. (4)I, IV

Official answer

Option 1

NTA final key.

Chapter
Organic Chemistry: Some Basic Principles and Techniques
Topic
Alkanes and Free Radicals
Idea tested
Free Radical Stability Trends

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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.