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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 II covers organic chemistry and spectroscopy.

UPSC Civil Services (Mains), Chemistry optional · 2024 · Paper II

Q5(b). P, Q and R from an enyne

Question

Predict the structures of P, Q and R in the following sequence of reactions: [2-methylhept-2-en-5-yne] —Na, NH₃(l)→ P —1) OsO₄, 2) NaHSO₃, H₂O→ Q —HIO₄→ R.

Answer in brief

P = (5E)-2-methylhepta-2,5-diene; Q = 2-methylheptane-2,3,5,6-tetraol; R = acetone + propanedial + ethanal.

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Topic notes: reagents for oxidation, reduction and hydroboration, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversBirch-type reductionNa/NH₃OsO₄ dihydroxylationperiodic acid cleavageenyneglycol cleavage

All parts of Question 5