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Saturday, 31 October

JEE Main 2021 · ChemistryMultiple choiceDiagram basedMediumMulti-step

JEE Main 27 August 2021, Shift 1, Chemistry Q42

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

In the following sequence of reactions, the final product D is : CH3−C≡C−H+NaNH2→A\mathrm{CH_3-C\equiv C-H + NaNH_2} \rightarrow \mathrm{A} A\mathrm{A} + [reagent drawn above the arrow] →B\rightarrow \mathrm{B} B\mathrm{B} →H2/Pd-C\xrightarrow{\mathrm{H_2/Pd\text{-}C}} C\mathrm{C} →CrO3\xrightarrow{\mathrm{CrO_3}} D\mathrm{D}

The figure, in words

Reaction scheme in one line: CH3-C≡C-H + NaNH2 gives A; A reacts with the reagent drawn above the second arrow, a skeletal zigzag chain with Br at its left end, an OH drawn above one upper vertex and CH3 at the right end; this gives B; then H2/Pd-C gives C; then CrO3 gives D.
  1. (1)H3C−CH=CH−CH(OH)−CH2−CH2−CH3\mathrm{H_3C-CH=CH-CH(OH)-CH_2-CH_2-CH_3}
  2. (2)H3C−CH2−CH2−CH2−CH2−C(=O)−H\mathrm{H_3C-CH_2-CH_2-CH_2-CH_2-C(=O)-H} (C=O drawn above the C, H at the right)
  3. (3)CH3−CH2−CH2−CH2−CH2−C(=O)−CH3\mathrm{CH_3-CH_2-CH_2-CH_2-CH_2-C(=O)-CH_3} (C=O drawn above the C)Official answer
  4. (4)CH3−CH=CH−CH2−CH2−CH2−COOH\mathrm{CH_3-CH=CH-CH_2-CH_2-CH_2-COOH}

Official answer

Option 3

NTA final key.

Chapter
Alcohols, Phenols and Ethers
Topic
Alkenes and Alkynes
Idea tested
Acetylide Ion Alkylation

Same idea in other shifts

Asked 2× in all
  1. 30 Jan 2024, Shift 1 · Q72Compound A formed in the following reaction reacts with B gives the product C. Find out A and B.…EasyOtherHas 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.