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lecture13-dept

lecture13-dept - • Vector diagrams are not adequate to...

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- 1 - CHEM / BCMB 4190/6190/8189 Introductory NMR Lecture 13
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- 2 - CHEM 4190/6190 The DEPT Experiment Interpreting 13 C NMR spectra: Very useful to know which signals belong to quaternary carbons, CH, CH 2 , and CH 3 J-modulated spin-echo experiment and refocused INEPT are useful but don't provide all the necessary information The DEPT experiment (Distorsionless Enhancement by Polarization Transfer) is now one of the most important techniques available for interpreting 1D 13 C NMR spectra
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- 3 - Pulse Sequence τ is 1/2J CH with J CH = 140 Hz is chosen to be Θ = 45˚, Θ =90˚, Θ = 135˚
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Unformatted text preview: • Vector diagrams are not adequate to explain the effect of this pulse and to understand this pulse sequence. • The following curves explain the effect of Θ on the intensities of signals • CH sub-spectrum: Θ2 = 90˚ or DEPT (90) • CH2 sub-spectrum: DEPT(45) - DEPT(135) • CH3 sub-spectrum: DEPT(45) + DEPT(135) - 0.707DEPT(90) • To compare absolute intensities the DEPT(90) must be collected with twice as many scans as for the other two DEPT experiments- 4 -Practically, it is sufficient to carry out two experiments, DEPT(90) and DEPT(135)...
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