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Saturday, 31 October

JEE Main 2020 · ChemistryMultiple choiceDiagram basedHardMulti-step

JEE Main 9 January 2020, Shift 1, Chemistry Q45

Question 45 of 75 in this shift, Chemistry question 20 of 25, Section A.

Identify (A) in the following reaction sequence : (A) Gives Positive iodoform test →(iii) Conc. H2SO4/Δ(i) CH3MgBr (ii) H+,H2O\xrightarrow[\text{(iii) Conc. } \mathrm{H_2SO_4}/\Delta]{\text{(i) } \mathrm{CH_3MgBr}\ \text{(ii) } \mathrm{H^+, H_2O}} (B) →O3/Zn,H2O\xrightarrow{\mathrm{O_3/Zn, H_2O}} (drawn product)

The figure, in words

Reaction scheme with the final product drawn: a ring with a circle inside, with a substituent O=C-H (O double-bonded to C, C bonded to H) on one vertex and, on the adjacent vertex, a carbon bonded to H3C, CH3 and a C=O carbon that has CH3 below it. Reagents printed: (i) CH3MgBr\mathrm{CH_3MgBr}, (ii) H+,H2O\mathrm{H^+, H_2O}, (iii) Conc. H2SO4/Δ\mathrm{H_2SO_4}/\Delta giving (B), then O3/Zn,H2O\mathrm{O_3/Zn, H_2O}. Options are drawn structures.
  1. (1)[figure: ring with a circle inside, attached to a CH=CH\mathrm{CH{=}CH} unit (double bond between the two carbons) that is bonded to a C=O\mathrm{C{=}O} carbon carrying CH3\mathrm{CH_3}]
  2. (2)[figure: ring with a circle inside, attached to a carbon bearing CH3\mathrm{CH_3} above, double bond to a carbon bearing CH3\mathrm{CH_3} at upper right and a C=O\mathrm{C{=}O} carbon below it carrying CH3\mathrm{CH_3}]
  3. (3)[figure: ring with a circle inside, attached to a carbon bearing CH3\mathrm{CH_3} above, double bond to a CH, then a C=O\mathrm{C{=}O} carbon carrying CH3\mathrm{CH_3}]
  4. (4)[figure: ring with a circle inside, attached to a CH, double bond to a carbon bearing CH3\mathrm{CH_3} at upper right and a C=O\mathrm{C{=}O} carbon below it carrying CH3\mathrm{CH_3}]Official answer

Official answer

Option 4

NTA final key (Jan 2020).

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. 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
  4. 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
  5. 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
  6. 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

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.