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Friday, 9 October

JEE Main 2021 · ChemistryMultiple choiceSingle correctMediumMulti-step

JEE Main 16 March 2021, Shift 2, Chemistry Q43

Question 43 of 90 in this shift, Chemistry question 13 of 30, Section A.

An unsaturated hydrocarbon X on ozonolysis gives A. Compound A when warmed with ammonical silver nitrate forms a bright silver mirror along the sides of the test tube. The unsaturated hydrocarbon X is :

The figure, in words

Option 4 is a drawn structure: CH3-C(CH3)= attached by a double bond to a cyclopropane ring.
  1. (1)CH3−C≡C−CH3\mathrm{CH_3-C\equiv C-CH_3}
  2. (2)(CH3)2C=C(CH3)2\mathrm{(CH_3)_2C=C(CH_3)_2}
  3. (3)HC≡C−CH2−CH3\mathrm{HC\equiv C-CH_2-CH_3}Official answer
  4. (4)[figure: isopropylidenecyclopropane, (CH3)2C=\mathrm{(CH_3)_2C=} cyclopropylidene, i.e. a cyclopropane ring double-bonded to a carbon bearing two CH3 groups]

Official answer

Option 3

NTA final key.

Chapter
Hydrocarbons
Topic
Alkenes and Alkynes
Idea tested
Alkyne Ozonolysis

Same topic in other shifts

All Alkenes and Alkynes questions
  1. 4 Apr 2026, Shift 1 · Q64An alkene (X) on ozonolysis followed by reduction gives following products. H−CHO\mathrm{H-CHO} (2 moles), OHC−CO−CHO\mathrm{OHC-CO-CHO}…HardDiagram basedHas a figure
  2. 4 Apr 2026, Shift 2 · Q64Compound (X) is subjected to the sequence of reactions as shown above. Molar mass of the major product (Y) formed is ________…MediumDiagram basedHas a figure
  3. 5 Apr 2026, Shift 1 · Q64"P" is a hydrocarbon of molecular formula:- C8H14\mathrm{C_8H_{14}}. On ozonolysis, "P" forms "Q". "Q" on treatment with alkali under reflux…HardDiagram basedHas a figure
  4. 6 Apr 2026, Shift 1 · Q66Given below are two statements: Statement I: 3-phenylpropene reacts with HBr and gives secondary alkyl bromide having a chiral carbon atom…MediumTwo statements
  5. 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
  6. 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

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 42 of the 174 JEE Main shifts held from 2017 to 2026.