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Friday, 9 October

JEE Main 2023 · ChemistryMultiple choiceDiagram basedMediumApplication

JEE Main 8 April 2023, Shift 2, Chemistry Q71

Question 71 of 90 in this shift, Chemistry question 11 of 30, Section A.

Major product 'P' formed in the following reaction is: [reaction: CH2=CH−CH2−CH2−COOH\mathrm{CH_2{=}CH{-}CH_2{-}CH_2{-}COOH} (pent-4-enoic acid, drawn as skeletal structure) →Br2, NaHCO3\xrightarrow{Br_2,\ NaHCO_3} P (Major product)]

The figure, in words

Stem shows skeletal pent-4-enoic acid with reagents Br2/NaHCO3; options are skeletal structures (three open-chain bromo acids and one bromo-lactone)
  1. (1)[structure: BrCH2CH2CH2CH2COOH\mathrm{BrCH_2CH_2CH_2CH_2COOH}]
  2. (2)[structure: CH3CH(Br)CH2CH2COOH\mathrm{CH_3CH(Br)CH_2CH_2COOH}]
  3. (3)[structure: BrCH2CH(Br)CH2CH2COOH\mathrm{BrCH_2CH(Br)CH_2CH_2COOH}]
  4. (4)[structure: five-membered lactone ring (γ\gamma-lactone) bearing a CH2Br\mathrm{CH_2Br} substituent, i.e. 5-(bromomethyl)oxolan-2-one]Official answer

Official answer

Option 4

NTA final key.

Chapter
Haloalkanes and Haloarenes
Topic
Alkenes and Alkynes
Idea tested
Halohydrin Formation Regiochemistry

Same topic in other shifts

All Alkenes and Alkynes questions
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  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.