Chapter 13 Notes

Chapter 13 Notes -...

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Chapter 13: Nuclear Magnetic Resonance Spectroscopy (NMR) Map of the carbon­hydrogen framework within a molecule Hydrogen (H1) and Carbon 13 (C13) nuclei are: These nuclei can be influenced by an external magnetic field (Bo) Lake and Stream Analogy There are two ways to align to a magnetic field: Parallel to B o Antiparallel to B o Title: Aug 1 ­ 10:09 AM (8 of 14)
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Energy absorption occurs and the lower energy (parallel) state "spin flips" to the higher energy alignment (antiparallel) The resonance frequency depends on: Unequal energy of these orientations Once the nuclei are oriented, they are irradiated with electromagnetic radiation (rf) parallel is slightly favored depending on BoStrength The nuclei are then considered to be "in resonance" with the applied field Title: Aug 1 ­ 10:18 AM (9 of 14)
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If a strong magnetic field is applied: The energy needed to generate NMR spectra is much lower than IR spectroscopy The Nature of NMR Absorptions: The absorption frequency for all H1and C13nuclei are not identical! Title: Aug 1 ­ 10:25 AM (10 of 14)
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Why? All nuclei are surrounded by electrons, each with their own magnetic fields (resulting from Bo) The effective field felt by nuclei: Nuclei are said to be "shielded" from the full effect of the applied field Each specific nucleus in a molecule is in a slightly different electronic
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This note was uploaded on 01/29/2012 for the course CHEM 234-54 taught by Professor Morrison during the Fall '09 term at UGA.

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Chapter 13 Notes -...

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