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UPSC Civil Services (Mains)

Chemistry optional

  • 2 papers
  • 250 marks each
  • 3 h per paper
  • 5 of 8 questions, Q1 and Q5 compulsory

Paper I covers physical and inorganic chemistry.

UPSC Civil Services (Mains), Chemistry optional · 2025 · Paper I

Q7(c). Stereoisomers of a doubly bridged dicobalt complex

Question

Draw the possible stereoisomers of the following complex and explain their optical activity. [(en)₂Co(μ-NH₂)(μ-NO₂)Co(en)₂]⁴⁺ [structure given in the paper]

Answer in brief

Three stereoisomers: a pair of enantiomers (ΔΔ and ΛΛ), each optically active, and one meso form (ΔΛ), optically inactive.

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Topic notes: Werner theory, isomerism, IUPAC names and valence bond theory of complexes, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversoptical isomerismmeso formbinuclear cobalt complexΔ and Λ configurationethylenediamine complexesenantiomers

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