BRAINCAKEFragmentation
Molecular ions are often unstable and break apart in the mass spectrometer. This is fragmentation. A molecular ion splits into a positive ion and a neutral radical:
M+ → X+ + Y•
Only the positive ion, X+, is detected. The radical has no charge, so it is not detected, but you can work out what was lost from the difference between the m/z of M+ and the fragment.
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Key terms in this lesson
- molecular ion
- The positive ion, M+, formed in a mass spectrometer when a molecule loses one electron; its mass gives the relative molecular mass.
- mass-to-charge ratio
- The ratio of the mass of an ion to its charge, given the symbol m/z, used to identify ions in a mass spectrum.
More in Analytical Techniques
- Bond Vibrations and IR Absorption
- Characteristic IR Absorptions
- Interpreting IR Spectra
- IR in Breathalysers and Pollution Monitoring
- Mass Spectrometry of Organic Compounds
- The Molecular Ion Peak
- The M+1 Peak
- Combining IR and Mass Spectra
All 10 lessons in Analytical Techniques · All OCR AS-level Chemistry topics