JEE Main 2021 · ChemistryMultiple choiceSingle correctMediumMulti-step

JEE Main 25 July 2021, Shift 1, Chemistry Q42

Question 42 of 90 in this shift, Chemistry question 12 of 30, Section A.

An Organic compound 'A'

\mathrm{C_4H_8}

on treatment with

\mathrm{KMnO_4/H^+}

yields compound 'B'

\mathrm{C_3H_6O}

. Compound 'A' also yields compound 'B' an ozonolysis. Compound 'A' is :

(1)But-2-ene
(2)Cyclobutane
(3)2-MethylpropeneOfficial answer
(4)1-Methylcyclopropane

Official answer

Option 3

NTA final key.

Chapter: Hydrocarbons
Topic: Alkenes and Alkynes
Idea tested: Reductive Ozonolysis Products

Same idea in other shifts

Asked 16× in all

4 Apr 2026, Shift 1 · Q64An alkene (X) on ozonolysis followed by reduction gives following products. $\mathrm{H-CHO}$ (2 moles), $\mathrm{OHC-CO-CHO}$ …HardDiagram basedHas a figure
5 Apr 2026, Shift 1 · Q64"P" is a hydrocarbon of molecular formula:- $\mathrm{C_8H_{14}}$ . On ozonolysis, "P" forms "Q". "Q" on treatment with alkali under reflux…HardDiagram basedHas a figure
3 Apr 2025, Shift 1 · Q65Which compound would give 3-methyl-6-oxoheptanal upon ozonolysis?MediumDiagram basedHas a figure
7 Apr 2025, Shift 1 · Q67Given below are two statements: Statement I: Ozonolysis followed by treatment with Zn, $\mathrm{H_2O}$ of cis-2-butene gives ethanal.…MediumTwo statements
7 Apr 2025, Shift 2 · Q66The number of optically active products obtained from the complete ozonolysis of the given compound is :…MediumOtherHas a figure
4 Apr 2024, Shift 2 · Q75In the above chemical reaction sequence "A" and "B" respectively areMediumDiagram basedHas a figure
29 Jan 2024, Shift 1 · Q89[figure: trans-2-butene drawn as CH $_3$ and H on the left carbon, H and CH $_3$ on the right carbon (CH $_3$ top-left, H bottom-left, H…EasyNumerical valueHas a figure
8 Apr 2023, Shift 1 · Q89Molar mass of the hydrocarbon (X) which on ozonolysis consumes one mole of $\mathrm{O_3}$ per mole of (X) and gives one mole each of…MediumNumerical value

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. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.