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Indian Forest Service (Mains)

Chemistry optional

  • 2 papers
  • 200 marks each
  • 3 h per paper

Paper II covers organic chemistry and spectroscopy.

Indian Forest Service (Mains), Chemistry optional · 2022 · Paper II

Q7(c). ESR of pyrazine

Question

Predict the ESR peaks for pyrazine and give their intensity ratios.

Answer in brief

Neutral pyrazine is closed-shell and normally ESR-silent; for its radical anion, two equivalent ¹⁴N and four equivalent H can give 25 resolved lines.

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The full model answer

As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.

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Topic notes: ESR spectroscopy, the g-value, hyperfine splitting and spin labels, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversESR spectroscopypyrazine radical anionhyperfine splitting2nI + 1 ruleintensity ratio

All parts of Question 7