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Saturday, 31 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 idea in other shifts

Asked 3× in all
  1. 4 Apr 2024, Shift 1 · Q78Given below are two statements : Statements I : Acidity of α\alpha-hydrogens of aldehydes and ketones is responsible for Aldol reaction.…MediumTwo statements
  2. 28 Jun 2022, Shift 2 · Q76Isobutyraldehyde on reaction with formaldehyde and K2CO3\mathrm{K_2CO_3} gives compound ‘A’. Compound ‘A’ reacts with KCN and yields compound…HardDiagram 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 108 of the 174 JEE Main shifts held from 2017 to 2026.