1 / 48

N uclear M agnetic R esonance Spectroscopy

N uclear M agnetic R esonance Spectroscopy. The nuclei of interest are primarily hydrogen and carbon 1 H NMR also called PMR 13 C NMR also called CMR. The Basis of NMR. NMR Active and Non-active Nuclei. Spinning proton resembles a tiny magnet. Protons in a magnetic field.

ballari
Download Presentation

N uclear M agnetic R esonance Spectroscopy

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Nuclear Magnetic Resonance Spectroscopy The nuclei of interest are primarily hydrogen and carbon 1H NMR also called PMR 13C NMR also called CMR

  2. The Basis of NMR

  3. NMR Active and Non-active Nuclei

  4. Spinning proton resembles a tiny magnet

  5. Protons in a magnetic field

  6. Absorption of energy causes nuclear “spin flip”

  7. The size of the magnet determines energy difference between spin states

  8. The NMR Event- What Causes “Spin Flip”?

  9. Magnetic Shielding by Electrons • The naked proton will come into resonance with a specific combination of radio energy and magnetic field strength. • But real protons are surrounded by electrons • Circulating electrons generate a small induced magnetic field that opposes the external magnetic field (B external) – (B induced) = B effective

  10. Shielding of Proton due to Induced Magnetic Field

  11. Chemical shift- position on the x-axis determined by shielding

  12. Field sweep NMR instrument

  13. FT NMR Spectrometer

  14. NMR Information 1H NMR spectrum contains 3 pieces of information: 1. 2. 3.

  15. 1. Chemical Shift

  16. 2. Integration of PeaksThe red curves represent the peak areas ( integration)

  17. 3. Peak SplittingThe (n+1) rule indicates the number of protons attached to neighboring carbon atoms A singlet indicates there are no protons on adjacent carbon atom A triplet indicates there are 2 protons on adjacent carbon atom

  18. Chemical Shift6 regions of NMR spectrum

  19. Table of Chemical Shifts

  20. Chemical Shift due to electron withdrawing effect triplet and quartet = ethyl pattern

  21. Chemical Shift for two Isomeric Esters: C4H8O2 The signals for both spectra are the same: a singlet, triplet & quartet.

  22. Splitting Patterns: n+1 Rule • A signal is split into multiple peaks by adjacent protons • The signal is split into n+1 peaks, where n = the number of equivalent adjacent protons

  23. Splitting Pattern for1,1,2-tribromoethane

  24. Splitting Pattern for1,1,2-trichloroethane

  25. Signal Splitting from one adjacent proton

  26. Splitting pattern for ethyl isopropyl ketone C6H12O

  27. Splitting Pattern for Ethyl Group

  28. Reciprocity of Coupling Constants • The distance between peaks of a multiplet are called coupling constants or J values

  29. Pascal’s Triangle

  30. NMR spectrum of p-xylene (no signal splitting)

  31. Interpreting Spectra • Look for diagnostic chemical shifts • Look for relative ratios (integration) • Analyze splitting patterns • Consult Tables of chemical shifts and Tables of coupling constants (J values)

  32. methyl propionate C4H8O2

  33. isopropanol C3H8O

  34. Long-Range Coupling: allyl alcohol C3H6O

  35. ethyl vinyl ether C4H8O

  36. C9H10O3

  37. C4H7O2Br

  38. C6H12O2

  39. C6H4BrI

  40. C8H10O

  41. More complex spectra to follow…

  42. C14H14

  43. C10H10O2

  44. C8H8O2

  45. C7H8O2

  46. C3H4O

  47. C6H10

  48. C4H6O

More Related