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lecture10-complexseqs

lecture10-complexseqs - CHEM BCMB 4190/6190/8189...

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- 1 - CHEM / BCMB 4190/6190/8189 Introductory NMR Lecture 10
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- 2 - Introduction to Complex Pulse Sequences Beyond simple 1D spectra: Simple 1D 1 H and 13 C spectra are not always sufficient for assigning even small organic compounds. The main problems are: 1) Assignment of the 1D spectra 2) Low S/N in spectra of insensitive nuclei with low natural abundance (e.g. 13 C, 15 N) Example: Neuraminic Acid derivative 1 Ac = CH 3 C O 1D C NMR Spectrum 13
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- 3 - We would also like to use the following information: 1) 13 C- 1 H correlations 2) The number of protons attach to one carbon 3) 1 H- 1 H correlations 4) 13 C- 13 C correlations etc. SOLUTION: Complex pulse sequences Use multiple pulses, delays and decoupling schemes Various pulses: hard pulses: 90˚x, 90˚y, 180˚x, 180˚y, etc. selective pulses: 90˚x, 90˚y, 180˚x, 180˚y, etc. pulse field gradients Various delays: fixed or variable delays Decoupling: for selective or broadband decoupling
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- 4 - To analyze the effect of complex pulse sequences we use: A) Vector Diagrams:
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