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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 Organic Chemistry Lab Structural Determination of Organic Compounds Lecture 2 – Intro to NMR January 22nd & 26th 2009
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
NMR Spin ½ nuclei 1H, 13C • Spin 1 nuclei2H (D), 14N Proton and Carbon NMR spectroscopy Spin 0 nuclei12C, 16O, 32S
100 E~ Radiowave 600 700 200 Nuclear Magnetic Resonance 400 400 INCREASING MAGNETIC FIELD
2.29 Chemical shift 7.04 Ha Hb 6 4 SiMe4 (TMS) Integration
3.75 Ha 6.82 Hb 6 4
1.50 Ha Downfield 9 Deshielded Upfield Hb Shielded 8.00 1
2.29 Ha 7.04 Upfield relative to Hb Shielded relative to Hb Downfield relative to Ha Deshielded relative to Ha Hb 6 4
Downfield Deshielded Upfield Shielded
2.45 4.56 9 CHCl3 6
0.87 9 2.42 NH2 1.04 2 2
2.14 5.80 3 2
3.66 2.05 3 3
0.08 2.04 9 3.76 TMS 3 2
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