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Learning Objectives

Learning Objectives. Use high resolution n.m.r spectrum of simple molecules (carbon, hydrogen & oxygen) to predict The different types of proton present The relative numbers of each type of proton The number of protons adjacent to a given proton Possible structures

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Learning Objectives

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  1. Learning Objectives • Use high resolution n.m.r spectrum of simple molecules (carbon, hydrogen & oxygen) to predict • The different types of proton present • The relative numbers of each type of proton • The number of protons adjacent to a given proton • Possible structures • Given a simple molecule predict features of the n.m.r spectrum. • Describe the use of D2O to identify –OH groups

  2. Nuclear Magnetic Resonance Spectroscopy

  3. Nuclear Magnetic Resonance Spectroscopy

  4. NuclearMagnetic Resonance Spectroscopy

  5. H H

  6. NuclearMagnetic Resonance Spectroscopy

  7. Nuclear Magnetic Resonance Spectroscopy

  8. NuclearMagneticResonanceSpectroscopy

  9. NuclearMagneticResonanceSpectroscopy

  10. Absorption peak corresponds to the radio frequency absorbed

  11. Only nuclei with an odd number of nucleons (neutrons and protons) possess a magnetic spin 1H (proton nmr) 13C

  12. The vast majority of proton NMR spectroscopy is performed on liquids. • You have a solid sample, what do you dissolve it in?

  13. structure spectrum

  14. Proton NMR Spectra

  15. Electrons around the nucleus shield it from the applied magnetic field. Different radio-frequencies are aborbed depending on the environment of the proton. CHEMICAL SHIFT is a measure of the magnetic field experienced by protons in different environments. CHEMICAL SHIFT is measured in ppm relative to TMS, Si(CH3)4 CHEMICAL SHIFT tells us about the types of protons present A B S O R T I O N CHEMICAL SHIFT

  16. A B S O R T I O N ABSORPTIONS The area under each peak is directly proportional to the number of protons responsible for the absorption These areas are most often presented as integration traces on the spectrum CHEMICAL SHIFT

  17. Your Turn

  18. Our Turn

  19. Different types of proton? Relative numbers of each type of proton?

  20. CH3CH2OH CH3CH2OH CH3CH2OH CH3CH2OH

  21. Predict 3 different types of proton Number protons is in ratio 1:2:3 Assign possible types of proton to chemical shifts obtained structure CH3CH2OH Expect 3 different types of proton Expect peaks in the following ranges 0.7-1.6ppm (CH3) 3.3-4.3ppm (CH2-O) 3.5-5.5ppm (OH) Expect integration 3:2:1 spectrum

  22. Learning Objectives • Use high resolution n.m.r spectrum of simple molecules (carbon, hydrogen & oxygen) to predict • The different types of proton present • The relative numbers of each type of proton • The number of protons adjacent to a given proton • Possible structures • Given a simple molecule predict features of the n.m.r spectrum. • Describe the use of D2O to identify –OH groups

  23. The number of absorption peaks tells us the number of different types of protons. The chemical shift helps us identifythe type of proton. The integration values tells us the relative number of protons.

  24. Nuclear Magnetic Resonance Spectroscopy Part 2

  25. Learning Objectives • Use high resolution n.m.r spectrum of simple molecules (carbon, hydrogen & oxygen) to predict • The different types of proton present • The relative numbers of each type of proton • The number of protons adjacent to a given proton • Possible structures • Given a simple molecule predict features of the n.m.r spectrum. • Describe the use of D2O to identify –OH groups

  26. CH3CH2OH CH3CH2OH CH3CH2OH CH3CH2OH

  27. why does this happen? Is it any use?

  28. CH3CH2OH C C O What name do we give to this effect? spin spin coupling

  29. CH3CH2OH H H H C C O H H H

  30. As a result of spin-spin coupling effects the signals are multiplets The n+1 rule For n adjacent protons We have n+1 peaks in the multiplet 2 adjacent protons Gives a triplet triplet What causes this triplet splitting pattern? The spin-spin coupling effects from the protons on the adjacent carbon.

  31. The n+1 rule For n adjacent protons We have n+1 peaks in the multiplet We have quartet How many protons on the adjacent carbon? quartet

  32. why does signal splitting this happen? Spin-spin coupling Is it any use? Yes. It tells us the number of protons attached to the adjacent carbon.

  33. Identifying O-H protons • O-H protons can absorb at different chemical shifts, dependant upon • Solvent used • Concentration of solvent • As a result it is difficult to identify O-H protons from chemical shifts • Trick D2O – sometimes called a “D2O shake”

  34. In CCl4 In D2O

  35. Identifying O-H protons • To identify O-H protons, • run the sample in a suitable solvent • Re-run the sample in D2O • Compare spectra • If the signal for the O-H proton dissapears in D2O • Evidence

  36. Learning Objectives • Use high resolution n.m.r spectrum of simple molecules (carbon, hydrogen & oxygen) to predict • The different types of proton present • The relative numbers of each type of proton • The number of protons adjacent to a given proton • Possible structures • Given a simple molecule predict features of the n.m.r spectrum. • Describe the use of D2O to identify –OH groups

  37. Learning Objectives • Use high resolution n.m.r spectrum of simple molecules (carbon, hydrogen & oxygen) to predict • The different types of proton present • The relative numbers of each type of proton • The number of protons adjacent to a given proton • Possible structures • Given a simple molecule predict features of the n.m.r spectrum. • Describe the use of D2O to identify –OH groups

  38. Learning Objectives • Use high resolution n.m.r spectrum of simple molecules (carbon, hydrogen & oxygen) to predict • The different types of proton present • The relative numbers of each type of proton • The number of protons adjacent to a given proton • Possible structures • Given a simple molecule predict features of the n.m.r spectrum. • Describe the use of D2O to identify –OH groups

  39. Learning Objectives • Use high resolution n.m.r spectrum of simple molecules (carbon, hydrogen & oxygen) to predict • The different types of proton present • The relative numbers of each type of proton • The number of protons adjacent to a given proton • Possible structures • Given a simple molecule predict features of the n.m.r spectrum. • Describe the use of D2O to identify –OH groups

  40. Your Turn

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