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Saturday, 31 October

JEE Main 2020 · ChemistryNumerical answerNumerical valueHardMulti-step

JEE Main 4 September 2020, Shift 1, Chemistry Q50

Question 50 of 75 in this shift, Chemistry question 25 of 25.

The number of chiral centres present in [B] is __________.

The figure, in words

Reaction scheme: a six-membered ring (hexagon, flat top, no double bonds drawn) with a short unlabelled line at the lower-left vertex; the right-hand vertex is bonded to CH (the two substituted vertices are separated by one ring vertex), which bears CH3 below and is bonded to C≡N. Reagents over the arrow: (i) C2H5MgBr\mathrm{C_2H_5MgBr}, (ii) H3O+\mathrm{H_3O^+}, giving [A]. Then second arrow with (i) CH3MgBr\mathrm{CH_3MgBr}, (ii) H2O\mathrm{H_2O}, giving [B].

Official answer

4.00

NTA final key (Sep 2020).

Chapter
Aldehydes, Ketones and Carboxylic Acids
Topic
Stereoisomerism
Idea tested
Chiral Centers

Same idea in other shifts

Asked 12× in all
  1. 4 Apr 2026, Shift 2 · Q65The following structures are [figure: stereocentre C with Br (up), CH3 (hashed, left), Me (down), Cl (wedge, right)] and [figure:…EasyDiagram basedHas a figure
  2. 8 Apr 2024, Shift 2 · Q89Total number of optically active compounds from the following is ___________. (1) Fischer projection: CH3\mathrm{CH_3} on top; H-C-OH;…MediumNumerical valueHas a figure
  3. 1 Feb 2024, Shift 1 · Q89Number of optical isomers possible for 2-chlorobutane ________.EasyNumerical value
  4. 11 Apr 2023, Shift 2 · Q79Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : A solution of the…MediumAssertion–reason
  5. 29 Jul 2022, Shift 2 · Q75Given below are two statements. Statement I: The compound [figure: compound (A), a drawn structure with a stereocentre bearing…MediumTwo statementsHas a figure
  6. 29 Jun 2022, Shift 1 · Q89Observe structures of the following compounds [figure: five structures] The total number of structures/compounds which possess asymmetric…EasyNumerical valueHas a figure
  7. 29 Jun 2022, Shift 2 · Q88The number of chiral alcohol(s) with molecular formula C4H10O\mathrm{C_4H_{10}O} is _____.MediumNumerical value
  8. 8 Jan 2020, Shift 1 · Q50The number of chiral centres in penicillin is ______.MediumNumerical value

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.