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Friday, 9 October

JEE Main 2021 · ChemistryMultiple choiceSingle correctHardMulti-step

JEE Main 25 July 2021, Shift 1, Chemistry Q44

Question 44 of 90 in this shift, Chemistry question 14 of 30, Section A.

[figure: 3,3-dimethylcyclopentanone (ketone C=O, gem-dimethyl on adjacent ring carbon) reacts with CH3CHO\mathrm{CH_3CHO}, NaOH to give 'P' (Major Product); then (i) I2/NaOH\mathrm{I_2/NaOH}, Filter (ii) Filtrate + HCl gives 'X'] Consider the given reaction, the product 'X' is :

The figure, in words

Reaction scheme starting from 3,3-dimethylcyclopentanone (as drawn: ketone with gem-dimethyl on the adjacent ring carbon) with CH3CHO/NaOH giving P, then I2/NaOH then HCl giving X.
  1. (1)[figure: 2,2-dimethyl-cyclopentanone ring bearing -COOH on the other alpha carbon]Official answer
  2. (2)[figure: 2,2-dimethylcyclopentanone ring bearing -CH(OH)CH3 on the other alpha carbon]
  3. (3)[figure: 2,2-dimethylcyclopentanone ring bearing -C(=O)CH3 on the other alpha carbon]
  4. (4)[figure: cyclopentane ring with OH and CH2CHO on the same carbon, adjacent carbon bearing gem-dimethyl]

Official answer

Option 1

NTA final key.

Chapter
Aldehydes, Ketones and Carboxylic Acids
Topic
Aldol and Cannizzaro
Idea tested
Cross-Aldol Condensation

Same topic in other shifts

All Aldol and Cannizzaro questions
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  3. 2 Apr 2025, Shift 1 · Q68Given below are two statements : Statement (I) : Vanillin ([structure: benzene ring with -CHO, -OH para to CHO and -OCH3 ortho to OH])…MediumTwo statementsHas a figure
  4. 3 Apr 2025, Shift 2 · Q68The major product (P) in the following reaction is : Ph−CO−CHO\mathrm{Ph{-}CO{-}CHO} →ΔKOH\xrightarrow[\Delta]{\mathrm{KOH}} P (Major Product)MediumDiagram basedHas a figure
  5. 8 Apr 2025, Shift 2 · Q68When [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…MediumSingle correctHas a figure
  6. 30 Jan 2024, Shift 2 · Q78m-chlorobenzaldehyde on treatment with 50% KOH solution yieldsEasyDiagram 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 42 of the 174 JEE Main shifts held from 2017 to 2026.