NMRlecture

NMRlecture - NMR Spectroscopy NMR Phenomenon Nuclear...

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NMR Spectroscopy
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2 NMR Phenomenon Nuclear Magnetic Resonance μ A spinning charged particle generates a magnetic field. A nucleus with a spin angular momentum will generate a magnetic moment ( μ ). B 0 If these tiny magnets are placed in an applied magnetic field ( B o ), they will adopt two different states - one aligned with the field and one aligned against the field. The energy difference between these two states is what we are observing with NMR.
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3 Nuclear Spin States B 0 E aligned against B 0 aligned with B 0 Energy difference between the states at a particular magnet strength. In the R f range of the EM Spectrum. When EM waves at this energy are directed at the nuclei - it will absorb. Spins will flip from lower energy to higher energy. At that energy, nuclei are “In Resonance”.
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4 NMR Active Nuclei Many nuclei are “NMR Active” Spin Quantum Number I 0 1 H -- I = ½ ; 13 C -- I = ½ 12 C, 16 O -- I = 0 -- Can’t be observed Other nuclei that are NMR active 2 H (D), 14 N, 19 F, 31 P
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5 NMR Instrumentation
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6 Magnetic Resonance Imaging NMR is the basis for MRI
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7 To summarize μ B 0 A spinning charged particle generates a magnetic field. A nucleus with a spin angular momentum will generate a magnetic moment (m). When placed in a magnetic field ( Bo ), they will adopt two different states - one aligned with the field and one aligned against the field. B 0 E aligned against B 0 aligned with B 0 Energy difference between the states at a particular magnet strength. In the R f range of the EM Spectrum.
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8 Methyl Acetate - Proton NMR H 3 C C O CH 3 O
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9 Methyl Acetate - Carbon NMR H 3 C C O CH 3 O solvent
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10 Electronic Shielding - Local Environments μ B 0 B effective B local B effective = B 0 - B local Actual magnetic field felt by the nucleus
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11 Methyl Acetate - Proton NMR H 3 C C O CH 3 O
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12 Methyl Acetate - Carbon NMR H 3 C C O CH 3 O solvent C O
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Chemical Shift The difference in resonance frequency of a nuclei relative to a standard Most Shielded
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This note was uploaded on 12/06/2011 for the course CHEM 341 taught by Professor Sun during the Fall '08 term at ND State.

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NMRlecture - NMR Spectroscopy NMR Phenomenon Nuclear...

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