NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY..
- 1. To here! Nuclear Magnetic Resonance (NMR) Spectroscopy From here O Dr.R.Srinivasan Dean & Professor Dept of Pharmaceutical Chemistry & Analysis Faculty of Pharmacy Bharath Institute of Higher Education & Research
- 2. The Nobel Prize in Physics 1952 "for their development of new methods for nuclear magnetic precision measurements and discoveries in connection therewith " Felix Bloch Edward Mills Purcell
- 3. Magnetic nuclei are in resonance with external magnetic field if they absorb energy and spin-flip from low energy state (parallel orientation) to high energy state (antiparallel orientation).
- 4. 4 atomic nuclei in absence of magnetic field atomic nuclei in presence of external magnetic field atomic nuclei can either align parallel (lower E) or antiparallel (higher E)
- 5. Magnetic nuclei are in resonance with external magnetic field if they absorb energy and spin-flip from low energy state (parallel orientation) to high energy state (antiparallel orientation).
- 6. Dependence of the difference in energy between lower and higher nuclear spin levels of the hydrogen atom
- 7. Dependence of the difference in energy between lower and higher nuclear spin levels of the hydrogen atom Nuclei in different environments (i.e. with different amounts of electron density around them) will require different amounts of energy to flip to higher energy different spin state
- 8. 8 Magnetic: oAll nuclei with odd number of protons oAll nuclei with odd number of neutrons Nonmagnetic: oNuclei with even number of both protons and neutrons
- 9. Fig. 13-4, p. 444
- 10. 10
- 11. Really Old School: Continuous wave (CW) 40 MHz NMR spectrometer 1960
- 12. A little less old school: Continuous wave (CW) 60 MHz NMR spectrum 1964
- 13. Not quite so old school: 1980s 60 MHz
- 14. The Nobel Prize in Chemistry 1991 "for his contributions to the development of the methodology of high resolution nuclear magnetic resonance (NMR) spectroscopy" Richard R. Ernst
- 15. 900 MHz NMR spectrometer Center for Biomolecular NMR, Heinrich-Heine-Universit辰t D端sseldorf State-of-the-art
- 16. Colchitaxel, a coupled compound made from microtubule inhibitors colchicine and paclitaxel 16
- 17. Free-induction decay data and proton-decoupled 13C nuclear magnetic resonance spectra
- 18. Fig. 13-6, p. 447 13 C NMR spectrum 1-pentanol : 1 scan
- 19. Fig. 13-6, p. 447 13 C NMR spectrum 1-pentanol : 1 scan 13 C NMR spectrum 1-pentanol : 200 scans
- 20. The Nature of NMR Absorptions 1 H NMR spectrum 13 C NMR spectrum
- 21. The Nobel Prize in Chemistry 2002 "for his development of nuclear magnetic resonance spectroscopy for determining the three-dimensional structure of biological macromolecules in solution" Kurt W端thrich
- 22. The Nobel Prize in Medicine 2003 "for their discoveries concerning magnetic resonance imaging " Paul C. Lauterbur Sir Peter Mansfield
- 23. More energy to flip nucleus Less energy to flip nucleus , ppm chemical shift = observed from standard spectrometer in MHz H0 2 = gyromagnetic ratio (differs for each nucleus) = (obs) - (TMS) spectrometer in MHz
- 24. 24 Magnetically distinct 13 C NMR of methyl acetate Chemically equivalent nuclei always show the same absorption
- 25. 25 Magnetically distinct hydrogens and carbons!
- 26. Fig. 13-7, p. 448 77 ppm CDCl3
- 27. Fig. 13-7, p. 448 77 ppm CDCl3 sp3
- 28. 28
- 30. 30 For each molecule below: Determine the number of distinct carbon peaks Assign chemical shifts for each distinct carbon
- 31. Fig. 13-10a, p. 451
- 32. Information in a 1 H NMR spectrum 13 C NMR spectrum 1 H NMR spectrum
- 33. Table 13-2, p. 457
- 34. Table 13-3, p. 458
- 35. Table 13-3, p. 458 6.5 8.0
- 36. 36 1 H NMR Integration Area under each peak is proportional to number of protons causing that peak. Gives ratio, not always exact number!
- 38. Fig. 11-13, p. 424 Spin Spin Splitting Absorption of a proton can split into multiple peaks (multiplet) Tiny magnetic field produced by one nucleus affects magnetic field felt by neighboring nuclei
- 39. Fig. 13-13, p. 460
- 40. Fig. 13-13, p. 460 3.4130 3.4165 3.4270 3.4235 3.42 Chemical shift middle of multiplet
- 41. Common NMR splitting patterns
- 42. Fig. 11-15, p. 425 C3H7Br
- 43. Fig. 11-15, p. 425 C3H7Br 12 2
- 44. Fig. 11-16, p. 427 1.5 1.5 1 1 1 C10H12O2
- 46. Fig. 13-19, p. 466
- 47. Fig. 13-19, p. 466
- 50. p. 409
Editor's Notes
- #3: Since a nucleus is a charged particle in motion, it will develop a magnetic field. 1H and 13C have nuclear spins of 1/2 and so they behave in a similar fashion to a simple, tiny bar magnet. In the absence of a magnetic field, these are randomly oriented but when a field is applied they line up parallel to the applied field, either spin aligned or spin opposed. The more highly populated state is the lower energy spin state spin aligned situation. Two schematic representations of these arrangements are shown above.
- #5: Since a nucleus is a charged particle in motion, it will develop a magnetic field. 1H and 13C have nuclear spins of 1/2 and so they behave in a similar fashion to a simple, tiny bar magnet. In the absence of a magnetic field, these are randomly oriented but when a field is applied they line up parallel to the applied field, either spin aligned or spin opposed. The more highly populated state is the lower energy spin state spin aligned situation. Two schematic representations of these arrangements are shown above.
- #9: Figure 13.4: Schematic operation of an NMR spectrometer. A thin glass tube containing the sample solution is placed between the poles of a strong magnet and irradiated with rf energy.
- #18: Figure 13.6: Carbon-13 NMR spectra of 1-pentanol, CH3CH2CH2CH2CH2OH. Spectrum (a) is a single run, showing the large amount of background noise. Spectrum (b) is an average of 200 runs.
- #19: Figure 13.6: Carbon-13 NMR spectra of 1-pentanol, CH3CH2CH2CH2CH2OH. Spectrum (a) is a single run, showing the large amount of background noise. Spectrum (b) is an average of 200 runs.
- #26: Figure 13.7: Chemical shift correlations for 13C NMR.
- #27: Figure 13.7: Chemical shift correlations for 13C NMR.
- #28: List of shifts based on functional groups. Divide spectrum in half (sp2 vs sp3). EN atoms cause shift downfield (left). EN atoms attract electrons so more deshielded and come into resonance at a lower field.
- #31: Figure 13.10: DEPTNMR spectra for 6-methyl-5-hepten-2-ol. Part (a) is an ordinary broadband-decoupled spectrum, which shows signals for all eight carbons.
- #36: 2 kinds of equivalent protons. Different height peaks. Can measure yourself if get step as show. Get 1:3 ratio but there are 12 Hs so 3:9 which correlates to structure.
- #38: Figure 11.13 The 1H NMR spectrum of bromoethane, CH3CH2Br. The CH2Br protons appear as a quartet at 3.42 隆, and the CH3 protons appear as a triplet at 1.68 隆. Go to this books student companion site at www.cengage.com/chemistry/mcmurry to explore an interactive version of this figure.
- #39: Figure 13.13: The 1H NMR spectrum of bromoethane, CH3CH2Br. The CH2Br protons appear as a quartet at 3.42隆, and the CH3 protons appear as a triplet at 1.68隆.
- #40: Figure 13.13: The 1H NMR spectrum of bromoethane, CH3CH2Br. The CH2Br protons appear as a quartet at 3.42隆, and the CH3 protons appear as a triplet at 1.68隆.
- #42: Figure 11.15 The 1H NMR spectrum of 2-bromopropane. The CH3 proton signal at 1.71 隆 is split into a doublet, and the CHBr proton signal at 4.28 隆 is split into a septet. Note that the distance between peaksthe coupling constantis the same in both multiplets. Note also that the outer two peaks of the septet are so small as to be nearly lost.
- #43: Figure 11.15 The 1H NMR spectrum of 2-bromopropane. The CH3 proton signal at 1.71 隆 is split into a doublet, and the CHBr proton signal at 4.28 隆 is split into a septet. Note that the distance between peaksthe coupling constantis the same in both multiplets. Note also that the outer two peaks of the septet are so small as to be nearly lost.
- #44: Figure 11.16 The 1H NMR spectrum of p-methoxypropiophenone.
- #46: Figure 13.19: The 1H NMR spectrum of trans-cinnamaldehyde. The signal of the proton at C2 (blue) is split into four peaksa doublet of doubletsby the two nonequivalent neighboring protons.
- #47: Figure 13.19: The 1H NMR spectrum of trans-cinnamaldehyde. The signal of the proton at C2 (blue) is split into four peaksa doublet of doubletsby the two nonequivalent neighboring protons.