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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

Q8(a)(i). Doxepin: site of ionisation, m/z 58 ion and metastable ion

Question

For the following compound (doxepin): (i) Identify the site of initial ionisation under EI conditions. (ii) Draw the structure of the ion having m/z = 58. (iii) Calculate the m/z value of the metastable ion formed during the formation of the above ion. [structure given in the paper]

Answer in brief

Ionisation occurs at the nitrogen lone pair (M⁺· at m/z 279); m/z 58 is CH₂=N⁺(CH₃)₂; m* = 58²/279 = 12.06.

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Coversmass spectrometryα-cleavageiminium ionmetastable iondoxepinEI ionisation

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