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Saturday, 31 October

JEE Main 2022 · ChemistryMultiple choiceDiagram basedMediumMulti-step

JEE Main 29 July 2022, Shift 1, Chemistry Q78

Question 78 of 90 in this shift, Chemistry question 18 of 30, Section A.

Consider the following reaction sequence : [figure: 4-aminobenzonitrile (benzene ring with NH2\mathrm{NH_2} at top, CN at bottom) →(ii) H2O(i) AlH (i-Bu)2\xrightarrow[\mathrm{(ii)\ H_2O}]{\mathrm{(i)\ AlH\ (i\text{-}Bu)_2}} 'A' →dil NaOH, ΔCH3CHO\xrightarrow[\mathrm{dil\ NaOH,\ \Delta}]{\mathrm{CH_3CHO}} B (Major Product)] The product 'B' is :

The figure, in words

Reaction sequence from 4-aminobenzonitrile with DIBAL-H then H2O, then CH3CHO / dil NaOH, heat; options are para-substituted benzene rings.
  1. (1)OHC−C6H4−N=CH−CH3\mathrm{OHC-C_6H_4-N=CH-CH_3} (para-disubstituted benzene ring)
  2. (2)H2N−C6H4−CH=CH−CHO\mathrm{H_2N-C_6H_4-CH=CH-CHO} (para-disubstituted benzene ring)Official answer
  3. (3)H2N−C6H4−CH2−N=CH−CH3\mathrm{H_2N-C_6H_4-CH_2-N=CH-CH_3} (para-disubstituted benzene ring)
  4. (4)H2N−C6H4−C(=O)−N=CH CHO\mathrm{H_2N-C_6H_4-C(=O)-N=CH\ CHO} (para-disubstituted benzene ring)

Official answer

Option 2

NTA final key.

Chapter
Aldehydes, Ketones and Carboxylic Acids
Topic
Carboxylic Acids and Derivatives
Idea tested
DIBAL-H Selective Reduction

Same idea in other shifts

Asked 4× in all
  1. 25 Jul 2022, Shift 1 · Q75Which one of the following reactions does not represent correct combination of substrate and product under the given conditions ?MediumDiagram basedHas a figure
  2. 25 Feb 2021, Shift 1 · Q46Which one of the following reactions will not form acetaldehyde ?MediumSingle correct
  3. 2 Apr 2017 (offline) · Q60The major product obtained in the following reaction is : [reaction: bicyclic lactone (cyclopentene fused to a five-membered lactone, with…MediumSingle 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. 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.