Worksheet: Fragment Ions

In this worksheet, we will practice analyzing mass spectra to identify the likely composition of the fragment ions produced from an analyte.

Q1:

What does the presence of M-15, M-29, and M-43 mass spectral peaks correspond to?

  • ALoss of nitrogen atoms
  • BAlcohol degradation
  • CSequential loss of alkyl groups
  • DCarbocation rearrangements

Q2:

When the molecular ion is absent, which fragment ion peaks are aliphatic nitro compounds indicated by?

  • A 𝑚 / 𝑧 = 4 6 and 𝑚/𝑧=58, corresponding to NO2+ and CNO2+
  • B 𝑚 / 𝑧 = 3 0 and 𝑚/𝑧=46, corresponding to NO+ and NO2+
  • C 𝑚 / 𝑧 = 3 2 and 𝑚/𝑧=28, corresponding to O2 and N2

Q3:

What does the fragmentation pattern in a mass spectrum tell us about the sample material?

  • AWhich functional groups were present in the original molecule
  • BWhat kinds of impurities were present and how much of each was there
  • CHow many atoms of each element were present in the original molecule
  • DThe atomic compositions of segments of the molecule that can be reassembled virtually to determine the original structure

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