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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 · 2025 · Paper II

Q5(b). Starting material A and the intermediates

Question

Deduce the structure of the starting material (A) and all the intermediates formed in each step that would lead to the formation of the following product, (E)-5-methoxy-2,2-dimethylhex-3-ene, through the defined reactions: 1) NaNH₂, EtI; 2) Lindlar's cat., H₂; 3) NBS, ROOR, Δ; 4) NaOMe, MeOH. [structure of the product given in the paper]

Answer in brief

A = 3,3-dimethylbut-1-yne, (CH₃)₃C–C≡CH.

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

CoversLindlar catalystNBS allylic brominationWohl–Ziegleracetylide alkylation3,3-dimethylbut-1-yne

All parts of Question 5