Learn

Saturday, 31 October

JEE Main 2023 · ChemistryMultiple choiceSingle correctHardApplication

JEE Main 12 April 2023, Shift 1, Chemistry Q76

Question 76 of 90 in this shift, Chemistry question 16 of 30, Section A.

In the following reaction [figure: CH3-C(=O)-CH2-CH(CH3)-Br, (i) Mg (ii) H2O\mathrm{H_2O} -> 'A' (Major Product)] A is

The figure, in words

Skeletal structure of 4-bromopentan-2-one, i.e. CH3-C(=O)-CH2-CH(CH3)-Br, treated with (i) Mg, (ii) H2O giving 'A' (Major Product).
  1. (1)[figure: 1,2-dimethylcyclopropan-1-ol; cyclopropane ring with OH and CH3 on one carbon and CH3 on an adjacent carbon]
  2. (2)[figure: CH3C(=O)CH2CH(CH3)C(CH3)(OH)CH2CH(CH3)Br\mathrm{CH_3C(=O)CH_2CH(CH_3)C(CH_3)(OH)CH_2CH(CH_3)Br} skeletal structure, ketone C=O at the left end, tertiary C bearing CH3 and OH, Br on a terminal CH(CH3)]Official answer
  3. (3)[figure: CH3C(=O)CH2CH(CH3)MgBr\mathrm{CH_3C(=O)CH_2CH(CH_3)MgBr} skeletal structure]
  4. (4)[figure: CH3C(OH)2CH2CH(CH3)MgBr\mathrm{CH_3C(OH)_2CH_2CH(CH_3)MgBr} skeletal structure, gem-diol carbon bearing two OH]

Official answer

Option 2

NTA final key.

Chapter
Haloalkanes and Haloarenes
Topic
Nucleophilic Addition
Idea tested
Grignard Reagent Addition

Same idea in other shifts

Asked 7× in all
  1. 25 Jun 2022, Shift 2 · Q76In the given reaction 2A2\mathrm{A} →(iii) H2O / H+(i) 2 Mg, THF; (ii) Methyl benzoate\xrightarrow[\text{(iii) } \mathrm{H_2O\ /\ H^+}]{\text{(i) 2 Mg, THF; (ii) Methyl benzoate}} [drawn…MediumDiagram basedHas a figure
  2. 26 Jun 2022, Shift 1 · Q75[figure: drawn structure with the label MgBr at its upper end and the label MgBr at its lower end, the two joined by a bracket-shaped…HardOtherHas a figure
  3. 4 Aug 2021, Shift 2 · Q44The major products A and B in the following reaction sequence are [reaction scheme: see figure_note] (Ph = - C6H5\mathrm{C_6H_5})MediumDiagram basedHas a figure
  4. 27 Aug 2021, Shift 2 · Q44Which one of the following is the major product of the given reaction ? [reaction drawn: a fused bicyclic compound - a benzene ring (drawn…HardDiagram basedHas a figure
  5. 25 Jul 2021, Shift 2 · Q50A reaction of benzonitrile with one equivalent CH3MgBr\mathrm{CH_3MgBr} followed by hydrolysis produces a yellow liquid "P". The compound "P"…MediumSingle correct
  6. 9 Jan 2020, Shift 1 · Q45Identify (A) in the following reaction sequence : (A) Gives Positive iodoform test…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.