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Kcal/mol. 1.7 X 10 3. 5.7 X 10 5. 9.5 X 10 3. 4.8 X 10 2. 72. 1.2. 9.5 X 10 -3. 10 -4. EIMS. NMR. Nuclear Magnetic Resonance (NMR) Spectroscopy. To here!. From here…. The Nobel Prize in Physics 1952.
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Kcal/mol 1.7 X 103 5.7 X 105 9.5 X 103 4.8 X 102 72 1.2 9.5 X 10-3 10-4 EIMS NMR
Nuclear Magnetic Resonance (NMR) Spectroscopy To here! From here…
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
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).
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)
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).
Dependence of the difference in energy between lower and higher nuclear spin levels of the hydrogen atom
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
Magnetic: • All nuclei with odd number of protons • All nuclei with odd number of neutrons • Nonmagnetic: • Nuclei with even number of both protons and neutrons
Really Old School: Continuous wave (CW) 40 MHz NMR spectrometer 1960
1964 A little less old school: Continuous wave (CW) 60 MHz NMR spectrum
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
State-of-the-art 900 MHz NMR spectrometer Center for Biomolecular NMR, Heinrich-Heine-Universität Düsseldorf
Colchitaxel, a coupled compound made from microtubule inhibitors colchicine and paclitaxel
Free-induction decay data and proton-decoupled 13C nuclear magnetic resonance spectra
13C NMR spectrum 1-pentanol : 1 scan Fig. 13-6, p. 447
13C NMR spectrum 1-pentanol : 1 scan 13C NMR spectrum 1-pentanol : 200 scans Fig. 13-6, p. 447
The Nature of NMR Absorptions 1H NMR spectrum 13C NMR spectrum
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 Wüthrich
Sir Peter Mansfield Paul C. Lauterbur The Nobel Prize in Medicine 2003 "for their discoveries concerning magnetic resonance imaging"
More energy to flip nucleus Less energy to flip nucleus chemical shift d, ppm
Magnetically distinct 13C NMR of methyl acetate Chemically equivalent nuclei always show the same absorption
77 ppm CDCl3 Fig. 13-7, p. 448
sp3 77 ppm CDCl3 Fig. 13-7, p. 448
For each molecule below: • Determine the number of distinct carbon peaks • Assign chemical shifts for each distinct carbon
Information in a 1H NMR spectrum 1H NMR spectrum 13C NMR spectrum
6.5 – 8.0 Table 13-3, p. 458
1H NMR Integration Area under each peak is proportional to number of protons causing that peak. Gives ratio, not always exact number!
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 Fig. 11-13, p. 424
Chemical shift – middle of multiplet 3.4130 3.4165 3.4235 3.4270 d 3.42 Fig. 13-13, p. 460
C3H7Br Fig. 11-15, p. 425
12 C3H7Br 2 Fig. 11-15, p. 425
1.5 C10H12O2 1 1.5 1 1 Fig. 11-16, p. 427
C10H12O 4.5 4.5 3 3 3