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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 · 2023 · Paper II

Q5(a). Number of ¹H NMR signals in (A) and (B)

Question

How many signals would you expect in the ¹H NMR spectrum of the above compounds? Mark these protons. [structures (A) and (B) given in the paper]

Answer in brief

(A) shows seven signals. (B) is drawn without wedges; read as trans-1,2-dimethylcyclopropane it shows three signals, and the cis isomer would show four.

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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 →

Covers¹H NMR signalsequivalent protonsdiastereotopic protonschemical equivalence1,2-dimethylcyclopropane

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