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UPSC Combined Geo-Scientist

Chemist

  • 3 descriptive papers
  • 200 marks each
  • 3 h per paper

Mains Paper III covers analytical and organic chemistry.

UPSC Combined Geo-Scientist, Mains · 2022 · Mains Paper III

Q6(a). Cyclohexanone: self-condensation with NaOH, none with LDA

Question

Cyclohexanone is known to undergo self-condensation reaction when treated with aqueous NaOH. However, no such reaction is observed when treated with LDA (lithium diisopropylamide). Give proper reasoning.

Answer in brief

NaOH gives a little enolate beside much ketone, so the two react (aldol); LDA converts all the ketone into its lithium enolate, leaving no C=O for the enolate to attack.

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Topic notes: carbonyl additions and condensations, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversaldol condensationLDAlithium enolatecyclohexanonekinetic enolate

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