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?

  • ACarbocation rearrangements
  • BLoss of nitrogen atoms
  • CAlcohol degradation
  • DSequential loss of alkyl groups

Q2:

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

  • A𝑚/𝑧=46 and 𝑚/𝑧=58, corresponding to NO2+ and CNO2+
  • B𝑚/𝑧=32 and 𝑚/𝑧=28, corresponding to O2 and N2
  • C𝑚/𝑧=30 and 𝑚/𝑧=46, corresponding to NO+ and NO2+

Q3:

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

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

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