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Interpretation of Electron Impact Mass Spectra - Fragmentation mechanisms and rules

Interpretation of Electron Impact Mass Spectra - Fragmentation mechanisms and rules Lecture 2 2015 in Applied Spectrocopy Torben Lund RUC. Electron impact ionization (EI). ABC + e -  ABC +. + e - + e - 70 eV Molecular ion (1 eV) 55 eV + 0.1 eV

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Interpretation of Electron Impact Mass Spectra - Fragmentation mechanisms and rules

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  1. Interpretation of Electron Impact Mass Spectra - Fragmentation mechanisms and rules Lecture 2 2015 in Applied Spectrocopy Torben Lund RUC

  2. Electron impact ionization (EI) ABC + e- ABC+. + e- + e-70 eV Molecular ion (1 eV) 55 eV + 0.1 eV ABC+.  AB+ + C. ABC+.  A. + BC+ AB+  A + B+ Mass spectrum

  3. Ionization mechanisms in EI mass spectrometry Four mechanisms: sai rH

  4. s - cleavage

  5. a-cleavage

  6. rH : McLafferty rearangement

  7. EI-Mass Spectra of different functional groups • Alkenes • Alkyl substituted aromatic compounds • Alcohols • Aldehydes • Ketones • Carboxylic acids • Esters • Amines

  8. Alkenes: m/z =41

  9. Alkyl benzenes

  10. Alkylbenzenes

  11. Alcohols (R-OH): M-18, Loss of alkyl groups

  12. Alchohols

  13. Alchohols: Loss of alkyl group, M-18

  14. Phenols: M-1, M-28, M-29

  15. Aromatic aldehydes: M-1, M-29Alifatic aldehydes: m/z = 29, M-29, M-43

  16. Alifatic Ketones: M-15, M-29, M-43, m/z = 43, m/z = 58, 72, 86

  17. Ketones (1)

  18. Aromatic ketones: m/z =105, 120

  19. Methyl Esters: M-31, m/z =59, 74

  20. Esters

  21. Carboxylic Acids: M-17, M-45, m/z = 45, 60

  22. Interpretation of Electron Impact Mass Spectra - Fragmentation mechanisms and rules Lecture 3 2015 in Applied Spectrocopy Torben Lund RUC

  23. Amines: Nitrogen rule obeyed, a-cleavage, m/z = 30

  24. Alkylamines

  25. Aromatic Amines

  26. Nitriles, R-CN

  27. Nitro compounds

  28. Halides, R-X , X = Cl, Br, I

  29. Halides, X = Cl and Br

  30. Ethers

  31. Pavia 10c

  32. Problem 6 p. 126 Yellow problembook

  33. Problem 8 p 128

  34. b-cleavage

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