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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 · 2023 · Paper II

Q6(d). Meaning of a coupling constant

Question

Define proton NMR coupling constant, explain its field dependence, and compare coupling constants for two vicinal protons.

Answer in brief

J is a scalar spin-coupling frequency measured in Hz; it is essentially independent of magnetic field, and JAB = JBA.

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

Coverscoupling constant Jspin–spin couplingfield independenceKarplus equationvicinal coupling

All parts of Question 6