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Electron Impact Mass Spectra: Fragmentation Mechanisms & Rules

Delve into the interpretation of electron impact mass spectra focusing on fragmentation mechanisms and rules. Explore ionization mechanisms and mass spectrum interpretation of various functional groups such as alkenes, alcohols, ketones, and more.

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Electron Impact Mass Spectra: Fragmentation Mechanisms & 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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