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Saturday, 31 October

JEE Main 2025 · ChemistryMultiple choiceSingle correctMediumApplication

JEE Main 8 April 2025, Shift 2, Chemistry Q68

Question 68 of 75 in this shift, Chemistry question 18 of 25, Section A.

When [structure: CH3C(=O)CH2CH2CH2CH2CHO\mathrm{CH_3C(=O)CH_2CH_2CH_2CH_2CHO}, a skeletal zigzag chain with a methyl ketone at one end and an aldehyde (C=O with H) at the other] undergoes intramolecular aldol condensation, the major product formed is :

The figure, in words

Stem shows the skeletal formula of a keto-aldehyde: CH3-C(=O)-(CH2)4-CHO.
  1. (1)[figure: cyclohept-2-en-1-one, seven-membered ring with C=O and an adjacent C=C]
  2. (2)[figure: 2-methylcyclopent-2-en-1-one, five-membered ring with C=O, adjacent ring C=C, methyl on the alkene carbon next to C=O]
  3. (3)[figure: 1-acetylcyclopentene, five-membered ring with ring C=C and an acetyl group on the alkene carbon]Official answer
  4. (4)[figure: 2-methylcyclopent-1-ene-1-carbaldehyde, five-membered ring with C=C, CHO on one alkene carbon and methyl on the other]

Official answer

Option 3

NTA final key.

Chapter
Aldehydes, Ketones and Carboxylic Acids
Topic
Aldol and Cannizzaro
Idea tested
Intramolecular Aldol

Same idea in other shifts

Asked 5× in all
  1. 12 Apr 2023, Shift 1 · Q77[figure: Me−C(=O)\mathrm{Me-C(=O)}-(zig-zag chain)-C(=O)−CH3\mathrm{C(=O)-CH_3} --OEt−\mathrm{OEt^-}, Δ\Delta--> 'A' major Product] A in the above…MediumSingle correctHas a figure
  2. 30 Jun 2022, Shift 1 · Q76Which among the following will be the major product of the given reaction ? [structure: skeletal chain: a terminal bond to a C=O carbon (O…MediumDiagram basedHas a figure
  3. 26 Feb 2021, Shift 2 · Q44Identify A in the given chemical reaction. [structure drawn: benzene ring with two adjacent CH2CH2CHO\mathrm{CH_2CH_2CHO} substituents]…MediumDiagram basedHas a figure
  4. 9 Jan 2020, Shift 2 · Q44In the following reaction A is : A…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.