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Saturday, 31 October

JEE Main 2022 · ChemistryMultiple choiceOtherHardMulti-step

JEE Main 26 June 2022, Shift 1, Chemistry Q75

Question 75 of 90 in this shift, Chemistry question 15 of 30, Section A.

[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 line] + CH3−C(=O)−CH2−C(=O)−CH3\mathrm{CH_3-C(=O)-CH_2-C(=O)-CH_3} (each C=O drawn with O above) →\rightarrow 'A' →H2O\xrightarrow{\mathrm{H_2O}} 'B' Major Product Consider the above reaction sequence and identify the product B.

The figure, in words

Stem shows a drawn bis-MgBr structure plus a diketone; options are drawn ring structures with OH/CH3/C=O labels as described.
  1. (1)[structure: five-membered carbon ring with labels HO, OH, CH3 and CH3 attached to ring carbons]Official answer
  2. (2)[structure: six-membered carbon ring with OH at the top vertex and OH at the bottom vertex]
  3. (3)[structure: five-membered carbon ring with OH at the top vertex, OH at a lower-right vertex, and two H3C labels on the left side]
  4. (4)[structure: five-membered carbon ring with O= at the upper-left and upper-right vertices, an H3C label at the lower left and a CH3 label at the lower right]

Official answer

Option 1

NTA final key.

Chapter
Aldehydes, Ketones and Carboxylic Acids
Topic
Nucleophilic Addition
Idea tested
Grignard Reagent Addition

Same idea in other shifts

Asked 7× in all
  1. 12 Apr 2023, Shift 1 · Q76In the following reaction [figure: CH3-C(=O)-CH2-CH(CH3)-Br, (i) Mg (ii) H2O\mathrm{H_2O} -> 'A' (Major Product)] A isHardSingle correctHas a figure
  2. 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
  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.