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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

Q8(a)(iii). Number of ¹H NMR signals

Question

Count the number of peaks observed in the ¹H NMR spectrum of the following compounds (1) and (2). Justify your answer. [structures of 2-chlorobutane and 1,6-dimethylcyclohexa-1,4-diene given in the paper]

Answer in brief

2-Chlorobutane: 5 signals; 1,6-dimethylcyclohexa-1,4-diene: 8 signals.

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Topic notes: ¹H and ¹³C NMR: chemical shift, spin–spin coupling and coupling constants, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversNMR signalsdiastereotopic protonschemical equivalence2-chlorobutane¹H NMR

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