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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

Q5(f). Chemical and magnetic equivalence in styrene

Question

Identify chemically equivalent and magnetically equivalent protons in the drawn styrene molecule. [structure of styrene given in the paper]

Answer in brief

The two terminal vinyl H are neither chemically nor magnetically equivalent. The aromatic ortho pair and meta pair are chemically equivalent but generally not magnetically equivalent.

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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 →

Coverschemical equivalencemagnetic equivalencestyrene NMRdiastereotopic protonscoupling constants

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