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Indian Forest Service (Mains)

Chemistry optional

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

Paper II covers organic chemistry and spectroscopy.

Indian Forest Service (Mains), Chemistry optional · 2025 · Paper II

Q4(c)(i). Acidity and aromatic conjugate bases

Question

Rank the three displayed compounds in decreasing acidity. [structures of indene (I), fluorene (II) and a pentakis(trifluoromethyl)cyclopentadiene (III) given in the paper]

Answer in brief

III > I > II.

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The full model answer

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Topic notes: aromaticity (Hückel rule, antiaromaticity, annulenes, azulene, tropolone, fulvene, sydnones), with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversacidity of indene and fluorenecyclopentadienyl anionaromatic conjugate basepKaCF₃ inductive effect

All parts of Question 4