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Friday, 9 October

JEE Main 2021 · ChemistryMultiple choiceSingle correctMediumApplication

JEE Main 3 August 2021, Shift 2, Chemistry Q46

Question 46 of 90 in this shift, Chemistry question 16 of 30, Section A.

Which one of the following reagents are not suitable for the preparation of benzaldehyde from benzene?
  1. (1)a) CH3Cl\mathrm{CH_3Cl} + Anhyd. AlCl3\mathrm{AlCl_3}; b) CrO2Cl2\mathrm{CrO_2Cl_2} + CS2\mathrm{CS_2} / H3O+\mathrm{H_3O^+}
  2. (2)a) CH3Cl\mathrm{CH_3Cl} + Anhyd. AlCl3\mathrm{AlCl_3}; b) Cl2\mathrm{Cl_2}/Fe dark / H2O\mathrm{H_2O} (373K)Official answer
  3. (3)a) CO, HCl, Anhyd. AlCl3\mathrm{AlCl_3}
  4. (4)a) CH3Cl\mathrm{CH_3Cl} + Anhyd. AlCl3\mathrm{AlCl_3}; b) CrO3\mathrm{CrO_3}, (CH3CO)2O\mathrm{(CH_3CO)_2O}, H3O+\mathrm{H_3O^+} (Heat)

Official answer

Option 2

NTA final key.

Chapter
Aldehydes, Ketones and Carboxylic Acids
Topic
Aromatic Hydrocarbons
Idea tested
Gattermann-Koch Formylation

Same idea in other shifts

Asked 4× in all
  1. 8 Apr 2026, Shift 2 · Q72'xx' is the product which is obtained from benzene by reacting it with carbon monoxide and hydrogen chloride in the presence of cuprous…MediumNumerical value
  2. 9 Apr 2024, Shift 1 · Q75Identify major product "X" formed in the following reaction : [figure: benzene…EasySingle correctHas a figure
  3. 31 Jan 2024, Shift 2 · Q78Identify the name reaction. [reaction: benzene + CO, HCl --(anhydrous AlCl3_3/CuCl)--> benzaldehyde (C6_6H5_5CHO)]EasySingle correctHas 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. Lumi analyses 42 of the 174 JEE Main shifts held from 2017 to 2026.