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1 H NMR Interpretation Using the NMR Mosaic

1 H NMR Interpretation Using the NMR Mosaic. Each peak represents a fragment of the molecule. Peak carries three critical pieces of information Integration : how many hydrogens on that fragment Chemical shift : functional group on or next to the fragment

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1 H NMR Interpretation Using the NMR Mosaic

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  1. 1H NMR Interpretation Using the NMR Mosaic

  2. Each peak represents a fragment of the molecule Peak carries three critical pieces of information • Integration: how many hydrogens on that fragment • Chemical shift: functional group on or next to the fragment • Multiplicity: how many next-door hydrogens

  3. Integration • RELATIVE number of hydrogens • Measure rise of line over peak C3H7Cl 2H 2H 3H

  4. Chemical Shifts • Functional groups on or next to fragment OH, NH Alkene Carboxylic acid hydrogen Adjacent to Oxygen Adjacent to Cl, Br, I Aldehyde hydrogen Adjacent to double bond Alkane-like Aromatic

  5. Chemical Shifts C3H7Cl Next to Cl Alkane-like

  6. Multiplicity (Splitting) • NEIGHBOR hydrogens = number of peaks -1

  7. Multiplicity (Splitting) 3 peaks (triplet) 2 neighbor H’s (probably CH2) 3 peaks (triplet) 2 neighbor H’s (CH2) 6 peaks (hextet) 5 H’s (CH3 & CH2)

  8. Create Molecule: Put pieces together Peak is a CH3 -No Functional Group -Next to CH2 C3H7Cl Peak is a CH2 -Next to Cl -Next to CH2 Peak is a CH2 -No Funct. Grp. -Next to CH2 -Next to CH3

  9. The NMR Mosaic can help • Reminds you to use integration AND chemical shift AND multiplicity • Helps you visualize how the pieces fit together • Helps you recognize mistakes in interpretation • Helps you interpret complex splitting

  10. Steps for Solving 1H NMR Spectra • Calculate integration for each peak • #H = peak integration x (total # H’s / total integration) • Smallest peak is often 1H • Peaks ~1d are often 3H (methyl) • Determine number of adjacent hydrogens from splitting • - Number of peaks = n+1, where n = number of adjacent • hydrogens • - Attach appropriate static cling(s) • Determine presence of functional group(s) • - Attach functional group static cling(s) • - Choose functional group Mosaic piece(s)

  11. Calculate # H’s for each peak C3H7Cl

  12. Calculate # H’s for each peak C3H7Cl 2H 2H 3H

  13. H | ─C─ | H Make NMR Mosaic Pieces: C3H7Cl

  14. CH2 H | ─C─ | H Make NMR Mosaic Pieces: C3H7Cl

  15. CH2 Funct. Grp. H | ─C─ | H Make NMR Mosaic Pieces: C3H7Cl

  16. CH2 Funct. Grp. H | ─C─ | H Make NMR Mosaic Pieces: C3H7Cl X-

  17. CH2 Funct. Grp. H | ─C─ | H Make NMR Mosaic Pieces: C3H7Cl X- H | ─C─ | H

  18. CH2 Funct. Grp. H | ─C─ | H Make NMR Mosaic Pieces: C3H7Cl X- H | ─C─ | H CH3

  19. H | ─C─ | H CH2 H | ─C─ | H Funct. Grp. CH3 CH2 Make NMR Mosaic Pieces: C3H7Cl X-

  20. H | ─C─ | H CH2 H | ─C─ | H Funct. Grp. CH3 CH2 Make NMR Mosaic Pieces: C3H7Cl H | H─C─ | H X-

  21. H | ─C─ | H CH2 H | ─C─ | H Funct. Grp. CH3 CH2 H | H─C─ | H CH2 Make NMR Mosaic Pieces: C3H7Cl X-

  22. Fit pieces together Great! Errors. Great! Error.

  23. H | ─C─ | H CH2 H | ─C─ | H Funct. Grp. CH3 CH2 H | H─C─ | H CH2 Make NMR Mosaic Pieces: C3H7Cl X- 1-chloropropane

  24. C6H12O2

  25. ─O ─ Funct. Grp. CH H | ─C─ | H C6H12O2

  26. O || ─ C ─ ─O ─ Funct. Grp. Funct. Grp. H | H─C─ | H CH H | ─C─ | H C6H12O2

  27. CH2 CH3 O || ─ C ─ H | ─C─ | ─O ─ Funct. Grp. Funct. Grp. CH3 H | H─C─ | H CH H | ─C─ | H C6H12O2

  28. CH2 CH3 H | H─C─ | H H | H─C─ | H O || ─ C ─ H | ─C─ | CH CH ─O ─ Funct. Grp. Funct. Grp. CH3 H | H─C─ | H CH H | ─C─ | H C6H12O2

  29. CH2 CH3 H | H─C─ | H H | H─C─ | H O || ─ C ─ H | ─C─ | CH CH ─O ─ Funct. Grp. Funct. Grp. CH3 H | H─C─ | H CH H | ─C─ | H C6H12O2: Isobutyl acetate Must Watch Chemical Shifts!

  30. C7H14O2

  31. H | ─C─ | ─O ─ Funct. Grp. CH3 CH3 C7H14O2

  32. O || ─ C ─ H | ─C─ | H H | ─C─ | ─O ─ Funct. Grp. Funct. Grp. CH2 CH3 CH3 C7H14O2

  33. O || ─ C ─ H | ─C─ | H H | ─C─ | H | ─C─ | H CH2 ─O ─ Funct. Grp. Funct. Grp. CH2 CH3 CH3 CH3 C7H14O2

  34. H | H─C─ | H H | H─C─ | H O || ─ C ─ H | ─C─ | H H | ─C─ | H | ─C─ | H CH CH CH2 ─O ─ Funct. Grp. Funct. Grp. CH2 CH3 CH3 CH3 C7H14O2 (2 of these)

  35. H | H─C─ | H H | H─C─ | H O || ─ C ─ H | ─C─ | H H | ─C─ | H | ─C─ | H CH CH CH2 ─O ─ Funct. Grp. Funct. Grp. CH2 CH3 CH3 CH3 H | H─C─ | H CH2 C7H14O2 (2 of these)

  36. H | H─C─ | H H | H─C─ | H O || ─ C ─ H | ─C─ | H H | ─C─ | H | ─C─ | H CH CH CH2 ─O ─ Funct. Grp. Funct. Grp. CH2 CH3 CH3 CH3 H | H─C─ | H CH2 C7H14O2: Isopropyl butyrate

  37. C6H11O2Cl

  38. H | ─C─ | H CH3 ─O ─ Funct. Grp. C6H12O2Cl

  39. H | ─C─ | H CH3 H | ─C─ | H ─O ─ Funct. Grp. Funct. Grp. CH2 C6H12O2Cl X-

  40. H | ─C─ | H CH3 H | ─C─ | H H | ─C─ | H ─O ─ Funct. Grp. Funct. Grp. Funct. Grp. CH2 CH2 C6H12O2Cl X-

  41. H | ─C─ | H H | ─C─ | H CH2 CH3 H | ─C─ | H H | ─C─ | H ─O ─ Funct. Grp. Funct. Grp. Funct. Grp. CH2 CH2 CH2 C6H12O2Cl X-

  42. H | ─C─ | H H | ─C─ | H CH2 CH3 H | ─C─ | H H | ─C─ | H ─O ─ Funct. Grp. Funct. Grp. Funct. Grp. CH2 CH2 H | H─C─ | H CH2 CH2 C6H12O2Cl X-

  43. H | ─C─ | H H | ─C─ | H CH2 X- CH3 O || ─ C ─ H | ─C─ | H H | ─C─ | H ─O ─ Funct. Grp. Funct. Grp. Funct. Grp. CH2 CH2 H | H─C─ | H CH2 CH2 C6H12O2Cl: Ethyl 4-chlorobutyrate

  44. NMR Mosaic Simplifies Interpretation of Complex Multiplets • Adjoining pieces specify connectivity • Interpretation is no longer “impossible”

  45. Example: C4H9Cl

  46. CH2 H | ─C─ | Funct. Grp. CH3 Example: C4H9Cl X-

  47. H | ─C─ | H CH2 H | ─C─ | Funct. Grp. CH3 Example: C4H9Cl X- Undetermined Splitting

  48. H | ─C─ | H CH2 H | H─C─ | H H | ─C─ | CH Funct. Grp. CH3 Example: C4H9Cl X- Undetermined Splitting

  49. H | ─C─ | H CH2 H | H─C─ | H H | ─C─ | CH Funct. Grp. CH3 H | H─C─ | H CH2 Example: C4H9Cl X- Undetermined Splitting

  50. H | ─C─ | H CH2 H | H─C─ | H H | ─C─ | CH Funct. Grp. CH3 H | H─C─ | H CH2 Example: C4H9Cl X- Undetermined Splitting

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