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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 · 2024 · Paper II

Q5(e). Number of ¹H NMR signals and order of chemical shift

Question

In the ¹H NMR spectrum of the following compounds (I, II, III), how many signals will be observed? In each case, label and arrange the hydrogens in the order of increasing chemical shift. [structures given in the paper]

Answer in brief

Each compound shows three signals: I (4 : 4 : 2), II (4 : 2 : 2), III (2 : 2 : 4). Order in every case: Ha < Hb < Hc.

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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 NMRchemical shiftnumber of signalsanthracenenorbornadienering current

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