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Measurements and interpretations of NMR spectra

Uppsala University Department of Chemistry Organic Chemistry. NMR-Spectroscopy NV1 Project. Measurements and interpretations of NMR spectra. Joan Bertrand Alar Ainla. 2005. Compound 1. We knew formula C 5 H 8 O 2 So DBE=2. Recorded spectra (300MHz). Proton (H) spectrum

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Measurements and interpretations of NMR spectra

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  1. Uppsala University Department of Chemistry Organic Chemistry NMR-Spectroscopy NV1 Project Measurements and interpretations of NMR spectra Joan Bertrand Alar Ainla 2005

  2. Compound 1 • We knew formula C5H8O2 • So DBE=2

  3. Recorded spectra (300MHz) • Proton (H) spectrum • Carbon (C) spectrum • COSY • HSQC • HMBC

  4. C spectrum C=O C-O

  5. H spectrum 1.4ppm, integraal 3, doublet  Methyl, next to CH

  6. X X COSY Eliminate alternatives High shift, next to O probably

  7. X X COSY Left! COO

  8. Initially concluded structure

  9. HSQC (verify idea)

  10. HMBC

  11. Compound 1

  12. Compound 2 • Expected structure (Chinchonidin)

  13. Recorded spectra (300MHz) • Proton (H) spectrum • Carbon (C) spectrum • COSY • HSQC • HMBC • NOESY

  14. Proton spectrum

  15. Carbon spectrum

  16. HMBC and starting point Aliphatic protons and carbons Aromatic protons Aromatic and olefinic carbons Cross-peak Aromatic proton Aliphatic carbon

  17. HSQC  C-3, H-9

  18. HMBC  C-10 or C-11

  19. HSQC  C-10, C-11, H-10/11

  20. COSY  H-10, H-11 (verify)

  21. HMBC – Next starting point Olefinic carbon connected to aliphatic protons

  22. HSQC  H-14

  23. COSY  2 H-15 and H-13 Many alternatives Isolated. 2 H-15

  24. HSQCC-15, C-13, C/H-12, C/H-16 Two carbon peaks in Vicinity. CH, CH2 peaks Why we dont have any other alternative?

  25. HMBC  C-18 and C-17 H-11, H-12 C-17 H-16 and H-10 are closer to C-18

  26. HSQC H 17 and 18

  27. Aliphatic region assignedAromatic ????

  28. COSY H-2

  29. HMBC  Looking for a next step Singlet. 3H High shift, similar to –O-Met Missing proton??

  30. CH3 O Structure

  31. HMBC  C-Met, C-6

  32. NOESY  H-8, H-7, H-5 Shift!

  33. HSQC  C-8, (C-7/5)

  34. HMBC  C-7 and C-5

  35. HMBC  unprotonated carbons C-4, C-4a, C-8a C-8a C-4a, J3 more sensitive C-8a C-4a, J3 more sensitive Thus C-4

  36. All signals assigned!

  37. Stereochemistry NOESY H-16 pointing downwards H-16 pointing downwards H-18 pointing to H-16 H-17 pointing toward H-13 H-11 pointing upwards

  38. Finally everything is assigned 

  39. Conclusion • This project was … • A lot of interesting challenge • A lot of mind boggling thoughts • A lot of pleasure when the puzzle became finally solved 

  40. THANK YOU! "If we knew what it was we were doing, it would not be called research, would it?"- Albert Einstein

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