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CHEM 344

CHEM 344. Organic Chemistry Lab. Structural Determination of Organic Compounds Lecture 2 – Intro to NMR. January 22 nd & 26 th 2009. Speed of light (c) is constant for all wavelengths Frequency ( n ), the number of wavelengths per second, is inversely proportional to wavelength:

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CHEM 344

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  1. CHEM 344 Organic Chemistry Lab Structural Determination of Organic Compounds Lecture 2 – Intro to NMR January 22nd & 26th 2009

  2. Speed of light (c) is constant for all wavelengths • Frequency (n), the number of wavelengths per second, is inversely proportional to wavelength: n = c/l • Energy of a radiation is directly proportional to frequency E = hc/l = hn

  3. NMR Spin ½ nuclei 1H, 13C • Spin 1 nuclei2H (D), 14N Proton and Carbon NMR spectroscopy Spin 0 nuclei12C, 16O, 32S

  4. 100 E~ Radiowave 600 700 200 Nuclear Magnetic Resonance 400 400 INCREASING MAGNETIC FIELD

  5. 2.29 Chemical shift 7.04 Ha Hb 6 4 SiMe4 (TMS) Integration

  6. 3.75 Ha 6.82 Hb 6 4

  7. 1.50 Ha Downfield 9 Deshielded Upfield Hb Shielded 8.00 1

  8. 2.29 Ha 7.04 Upfield relative to Hb Shielded relative to Hb Downfield relative to Ha Deshielded relative to Ha Hb 6 4

  9. Downfield Deshielded Upfield Shielded

  10. 2.45 4.56 9 CHCl3 6

  11. 0.87 9 2.42 NH2 1.04 2 2

  12. 2.14 5.80 3 2

  13. 3.66 2.05 3 3

  14. 0.08 2.04 9 3.76 TMS 3 2

  15. Summary NMR – detailed info on molecular structure Different protons within the molecule give different signals # different protons = # signals Integration = # protons giving the signal Chemical shift value influenced by local structure of molecule (e.g. electronegative groups) Equivalent protons = same chemical shift Next time – spin-spin splitting, coupling constants…. Pages 383– 408 Solomons & Fryhle UW Edition

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