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NMR N uclear M agnetic R esonance

NMR N uclear M agnetic R esonance. Special NMR topics. Index. NMR-basics. H-NMR. NMR-Symmetry. Heteronuclear-NMR. Dynamic-NMR. NMR / Organometallic compounds. Special 1D-NMR. Inversion Recovery. Dinitrobenzene: T 1. 180. 90. t. H 4 /H 6. H 2. H 5. 180. 90. t.

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NMR N uclear M agnetic R esonance

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  1. NMRNuclear Magnetic Resonance SpecialNMR topics Index NMR-basics H-NMR NMR-Symmetry Heteronuclear-NMR Dynamic-NMR NMR / Organometallic compounds Special 1D-NMR

  2. Inversion Recovery

  3. Dinitrobenzene: T1 180 90 t H4/H6 H2 H5

  4. 180 90 t Inversion recovery : 13C t = 50 s D1= 5T1 t = 6 s t = 3 s t = 1.5 s t = 0.03 s T1 = tnull / ln2 = 1.443 * tnull e.g. C2 => T1 = 4.3 s (tnull=3 )

  5. One approach of reducing relaxation time is by the addition of paramagnetic relaxation reagent (Chromium III acetylacetonate => Cr(acac)3) Helping relaxation With Cr(acac)3 1s delay, 30o pulse Without Cr(acac)3

  6. Refocusing of field inhomogeneity

  7. CPMG used to get rid of broad signals 90 180 t Polystyrene (50,000) + camphor t = 1.5 ms

  8. Heteronuclear Decoupling

  9. Heteronuclear nOe For nuclei having positive g : (e.g. 13C) Decoupling proton can produce higher signals due to nOe. Enhancement is dependant on motion and distance between interacting nuclei As a consequence, quaternary carbons are much smaller than protonated carbons

  10. Heteronuclear nOe • Can yield higher positive signal for nuclei with positive g (e.g. 13C) • For nuclei with negative g(e.g. 29Si, 15N) can yield larger (negative) signals or for partial T1DD can null the signal!!! e.g. 15N {1H} S =A0+NOE= -4 S =A0+NOE= 0 S =A0+NOE= -1.5 50% NOE 20% NOE Without NOE S = A0 =1 100% NOE NOE=-1 NOE=-2.5 gH ~ -5 NOEmax 2 gN

  11. APTPulse Sequence

  12. Multiplet Modulation

  13. APT : 8 msec delay

  14. APT : 6 msec delay

  15. INEPT

  16. Comparing NOE Enhancement and INEPT Enhancement

  17. INEPT sequence

  18. Multiplet distortion in INEPT: 29Si

  19. Multiplet distortion in coupled INEPT: 13C

  20. Multiplet distortion in coupled INEPT: 13C

  21. 29Si – INEPT coupled

  22. Refocused INEPT

  23. Multiplicity Modulation : HX

  24. Multiplicity Modulation : XH2

  25. Multiplicity Modulation : XH3

  26. Decoupled INEPT: Menthol

  27. Optimum delay in decoupled INEPT

  28. Decoupled INEPT: compare normal and INEPT 29Si

  29. DEPT

  30. Intensity vs pulse angle

  31. DEPT-135 Menthol in Acetone-d6 DEPT-90 DEPT-90 DEPT-45 Normal 13C

  32. DEPT Ipsenol

  33. DEPT Editing

  34. ADEPT Editing

  35. Index NMR-basics H-NMR NMR-Symmetry Heteronuclear-NMR Dynamic-NMR NMR and Organometallic compounds Special 1D-NMR IR-basics

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