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Saturday, 31 October

JEE Main 2020 · ChemistryMultiple choiceDiagram basedMediumMulti-step

JEE Main 9 January 2020, Shift 1, Chemistry Q43

Question 43 of 75 in this shift, Chemistry question 18 of 25, Section A.

The major product (Y) in the following reactions is : CH3−CH(CH3)−C≡CH\mathrm{CH_3-CH(CH_3)-C{\equiv}CH} →H2OHgSO4, H2SO4\xrightarrow[\mathrm{H_2O}]{\mathrm{HgSO_4,\ H_2SO_4}} X X →(ii) Conc. H2SO4/Δ(i) C2H5MgBr, H2O\xrightarrow[\text{(ii) Conc. } \mathrm{H_2SO_4}/\Delta]{\text{(i) } \mathrm{C_2H_5MgBr,\ H_2O}} Y

The figure, in words

Reaction scheme drawn: CH3−CH−C≡CH\mathrm{CH_3-CH-C{\equiv}CH} with a CH3\mathrm{CH_3} above the CH, over an arrow labelled HgSO4, H2SO4\mathrm{HgSO_4,\ H_2SO_4} (above) and H2O\mathrm{H_2O} (below), giving X; then a second arrow from X labelled (i) C2H5MgBr, H2O\mathrm{C_2H_5MgBr,\ H_2O} (above) and (ii) Conc. H2SO4/Δ\mathrm{H_2SO_4}/\Delta (below) giving Y. Options are drawn chain structures.
  1. (1)[figure: CH3−C=C−CH3\mathrm{CH_3-C=C-CH_3} drawn with a double bond between the two middle carbons, CH3\mathrm{CH_3} attached above the first of them and CH2CH3\mathrm{CH_2CH_3} attached below the second]Official answer
  2. (2)[figure: CH3−CH−C=CH2\mathrm{CH_3-CH-C=CH_2} with CH3\mathrm{CH_3} attached above the CH and CH2CH3\mathrm{CH_2CH_3} attached below the C]
  3. (3)[figure: CH3−CH−C=CH−CH3\mathrm{CH_3-CH-C=CH-CH_3} with CH3\mathrm{CH_3} attached above the CH and CH3\mathrm{CH_3} attached below the C]
  4. (4)[figure: H3C−C−CH−CH3\mathrm{H_3C-C-CH-CH_3} with CH2\mathrm{CH_2} attached above the first C by a double bond and C2H5\mathrm{C_2H_5} attached below the CH]

Official answer

Option 1

NTA final key (Jan 2020).

Chapter
Hydrocarbons
Topic
Alkenes and Alkynes
Idea tested
Kucherov Alkyne Hydration

Same idea in other shifts

Asked 4× in all
  1. 6 Apr 2026, Shift 2 · Q65An optically active alkyl bromide C4H9Br\mathrm{C_4H_9Br}, reacts with ethanolic KOH to form major compound [A] which reacts with bromine to…MediumSingle correct
  2. 2 Apr 2025, Shift 1 · Q66An optically active alkyl halide C4H9Br\mathrm{C_4H_9Br} [A] reacts with hot KOH dissolved in ethanol and forms alkene [B] as major product…MediumSingle correct
  3. 24 Feb 2021, Shift 2 · Q44Which one of the following carbonyl compounds cannot be prepared by addition of water on an alkyne in the presence of HgSO4\mathrm{HgSO_4}…EasySingle correctHas 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.