Reading a Mass Spectrum
| Peak | What It Tells You |
|---|---|
| Molecular ion (M⁺) | Highest m/z peak (ignoring isotope peaks) → gives the relative molecular mass |
| Base peak | Most abundant fragment (tallest peak, set to 100%) |
| Fragment peaks | Differences between M⁺ and fragments reveal structural groups |
Common Fragment Losses
| m/z Loss | Fragment Lost |
|---|---|
| 15 | CH₃ (methyl) |
| 17 | OH (hydroxyl) |
| 18 | H₂O |
| 28 | CO or C₂H₄ |
| 29 | CHO (aldehyde) or C₂H₅ |
| 45 | OC₂H₅ or COOH |
AQA GCSE & IB Chemistry
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