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Saturday, 31 October

JEE Main 2024 · ChemistryMultiple choiceOtherMediumRecall

JEE Main 30 January 2024, Shift 1, Chemistry Q75

Question 75 of 90 in this shift, Chemistry question 15 of 30, Section A.

In the given reactions, identify the reagent A and reagent B. [Scheme: toluene reacts via two routes to give benzaldehyde. Route 1: "A" + (CH3CO)2O\mathrm{(CH_3CO)_2O}, 273-283 K, gives [Intermediate], then H3O+\mathrm{H_3O^+}, Δ\Delta gives benzaldehyde (CHO). Route 2: "B" + CS2\mathrm{CS_2} gives [Intermediate], then H3O+\mathrm{H_3O^+} gives benzaldehyde (CHO).]

The figure, in words

Toluene (CH3 on benzene ring) with two reaction routes to benzaldehyde: route 1 reagent A + (CH3CO)2O at 273-283 K then H3O+ with heat; route 2 reagent B + CS2 then H3O+.
  1. (1)A-CrO3\mathrm{CrO_3} B-CrO3\mathrm{CrO_3}
  2. (2)A-CrO3\mathrm{CrO_3} B-CrO2Cl2\mathrm{CrO_2Cl_2}Official answer
  3. (3)A-CrO2Cl2\mathrm{CrO_2Cl_2} B-CrO3\mathrm{CrO_3}
  4. (4)A-CrO2Cl2\mathrm{CrO_2Cl_2} B-CrO2Cl2\mathrm{CrO_2Cl_2}

Official answer

Option 2

NTA final key.

Chapter
Aldehydes, Ketones and Carboxylic Acids
Topic
Aromatic Hydrocarbons
Idea tested
Side-chain Oxidation

Same idea in other shifts

Asked 6× in all
  1. 4 Apr 2026, Shift 1 · Q72Consider the following sequence of reactions to give the major product (X) benzene…MediumNumerical valueHas a figure
  2. 5 Apr 2024, Shift 2 · Q89The product (C) in the following sequence of reactions has ________ π\pi bonds. n-propylbenzene (benzene ring bearing a three-carbon…MediumNumerical valueHas a figure
  3. 10 Apr 2023, Shift 1 · Q74The major product ‘P’ formed in the given reaction is [structure: naphthalene ring bearing CH2CH3\mathrm{CH_2CH_3} at one position of one…MediumDiagram basedHas a figure
  4. 26 Jun 2022, Shift 2 · Q72Oxidation of toluene to benzaldehyde can be easily carried out with which of the following reagents?MediumSingle correct
  5. 4 Aug 2021, Shift 1 · Q45Identify P in the given chemical reaction i) KMnO4\mathrm{KMnO_4}, KOH, heat ii) H3O+\mathrm{H_3O^+}EasyDiagram basedHas 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.