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Saturday, 31 October

JEE Main 2021 · ChemistryMultiple choiceOtherMediumApplication

JEE Main 26 August 2021, Shift 1, Chemistry Q45

Question 45 of 90 in this shift, Chemistry question 15 of 30, Section A.

The major products formed in the following reaction sequence A and B are : [figure: hexagonal ring joined to a carbonyl carbon (C=O) which carries CH3\mathrm{CH_3}; arrow with Br2\mathrm{Br_2} above and KOH below, giving A + B]

The figure, in words

Reactant: hexagonal ring (hexagon with inner circle) attached to a C(=O) carbon bearing CH3. Reagents on the arrow: Br2 above, KOH below. Option 2 drawings: Br labels on two ring vertices (upper-left and lower-left) in A and HO labels on two ring vertices (upper-left and lower-left) in B, with C(=O)-CH3 on the right vertex. Option 3 drawings: one Br label at the lower-left ring vertex in both A and B.
  1. (1)A = [figure: hexagonal ring bonded to C(=O)OK], B = CHBr3\mathrm{CHBr_3}Official answer
  2. (2)A = [figure: hexagonal ring bearing Br at two ring positions and the group C(=O)-CH3], B = [figure: hexagonal ring bearing HO at two ring positions and the group C(=O)-CH3]
  3. (3)A = [figure: hexagonal ring bearing Br on the ring and the group C(=O)-CH2-Br], B = [figure: hexagonal ring bearing Br on the ring and the group C(=O)-CH2-OH]
  4. (4)A = [figure: hexagonal ring bonded to C(=O)-CBr3], B = [figure: hexagonal ring bonded to CHO]

Official answer

Option 1

NTA final key.

Chapter
Aldehydes, Ketones and Carboxylic Acids
Topic
Aldol and Cannizzaro
Idea tested
Haloform Interference with Aldol

Same idea in other shifts

Asked 2× in all
  1. 27 Aug 2021, Shift 1 · Q44The structure of the starting compound P used in the reaction given below is : P…MediumDiagram 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.