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NUCLEAR MAGNETIC RESONANCE (NMR)

NUCLEAR MAGNETIC RESONANCE (NMR). WIDIASTUTI AGUSTINA ES, S.Si., M.Si. Nuclear Magnetic Resonance Spectroscopy (NMR) : Spectroscopic technique that provide information about amount and type of atomic molecule Hydrogen atoms 1 H NMR Carbon atoms 13 C NMR

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NUCLEAR MAGNETIC RESONANCE (NMR)

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  1. NUCLEAR MAGNETIC RESONANCE (NMR) WIDIASTUTI AGUSTINA ES, S.Si., M.Si.

  2. Nuclear Magnetic Resonance Spectroscopy (NMR) : Spectroscopic technique that provide information about amount and type of atomic molecule • Hydrogen atoms 1H NMR • Carbon atoms 13C NMR • Phosphor atoms 31P NMR

  3. NUCLEAR SPIN ATOM • Electron have quantum number ½ with a value of +1/2 and -1/2 - Spin Charge generates magnetic field so that electron act as a tiny magnet called a magnetic moment • This effect also valid for another atom. An atomic nucleus has an odd number and atomic number of the odd or both will have to have spin and produced magnetic moment • Nuclear Spin Rate depends on the quantum spin number , l, of nuclei

  4. NUCLEAR SPIN NUMBER Number of spin state = 2 l +1 l = nuclear spin quantum number

  5. SPIN STATE Nuclear atomic spin with + charge, generating a magnetic moment vector m + + m Without magnetic field, both spin state have the same energy + 1/2 - 1/2

  6. IN MAGNETIC FIELD (BO)

  7. RESONANCE In NMR spectroscopy, resonance is the energy absorption by the core-precision results in a change of spin nuclei from lower energy level to a higher energy level The precision results in a magnetic field oscillations and produce a "signal"

  8. quantized -1/2 -1/2 DE = hn DE In a strong magnetic field, a rotating nuclei absorbs radio frequency (resonance phenomena) +1/2 +1/2 Bo Magnetic Field

  9. LARMOR EQUATION g n = 2p Bo • =frequency of the radiation that comes, which will cause • the transition • = giromagnetic ratio • different for each atom (H, C, N) • B0= magnetic field

  10. Magnetic Field In organic compounds, hydrogen atoms are surrounded by electrons moving in the presence of a magnetic field. The movement of electrons around the nuclei of hydrogen atoms in the magnetic field result in Diamagnetic Current The area around the atomic nucleus that is formed by electrons are called DiamagneticShielding B Induced (opposed Bo) Bo Applied

  11. MEASUREMENT • Liquid Sample • Sample volume  0,5 mL • Solvent • 1H NMR = deuterated solvent • CDCl3, CDOH3, Acetone-d6, Benzene-d6 • Piridin-d5, DMSO-d6, D2O • 13C NMR = CHCl3, CHOH3, Acetone, Benzene • Piridin, DMSO, H2O • Sampel Amount = ≤ 50 mg

  12. 1H NMR

  13. INFORMATION FROM 1H NMR 1. Chemical Shift(, ppm), expressed as ppm(per million)  functional group 2. Integration  number of proton 3. Multiplicity(s, d, t, q, qi, sext., hept.) proton relationship 4. Coupling Constant(J, Hz)  type of proton relationship stereochemistryorposition of proton 5. Proton Signal: 0-15 ppm

  14. integration multiplicity Coupling constante standartTMS Chemical shift ppm H group= amount & type ofproton

  15. HYDROGEN EQUIVALENT Hydrogen Equivalent : Hydrogen that have a same chemical environtment • Compounds that have one hydrogen equivalent, producing one peak of proton NMR

  16. - Compounds that have two/three hydrogen equivalent, producing two/three peak of proton NMR

  17. How many proton signal??

  18. CHEMICAL SHIFT NMR signal is not measured by resonance position, but based on how far to shift from TMS, called CHEMICAL SHIFT Has a highly protected proton and carbon (appears on upfield region)

  19. PROTON CHEMICAL SHIFT Proton chemical shift depends on the frequency of tool used (shear difference for protons appear the same but measured in different tools) TMS shift in Hz downfield n 0 shift in Hz chemical shift = d = = ppm spectrometer frequency in MHz Any specific protons in a molecule will always appear at the same chemical shift (constant value)

  20. PROTON CHEMICAL SHIFT

  21. PROTON CHEMICAL SHIFT

  22. PROTON CHEMICAL SHIFT Factors affecting proton chemical shift : • Electronegatifity of the neighbour atoms • Hibridisation from the adjacent atoms • Diamagnetic Effect from the adjacent phi bond

  23. ELECTRONEGATIFITY d- d+ • Chlorine pull electron density away from carbon , caused electron density around the proton. • Chlorine caused proton to be “deshields” Cl C H d- d+ electronegative NMR CHART Deshieldingprotons,appears atlow field Shielding protons, appears at high field moredeshielding

  24. ELECTRONEGATIFITY Chemical Shift of X on CH3X CH3X CH3F CH3OH CH3Cl CH3Br CH3I CH4 (CH3)4Si X F O ClBr I H Si Electronegativity ofX 4.0 3.5 3.1 2.8 2.5 2.1 1.8 Geseran Kimia d 4.26 3.40 3.05 2.68 2.16 0.23 0 TMS Most deshielded

  25. ELECTRONEGATIFITY "deshielding" effect increased with increasing number of electronegative atoms most deshielded CHCl3 CH2Cl2CH3Cl 7.27 5.30 3.05 ppm “deshielding” effect decrease with increasing proton distance of electronegative atoms most deshielded -CH2-Br -CH2-CH2Br -CH2-CH2CH2Br 3.30 1.69 1.25 ppm

  26. HIBRIDISATION

  27. DIAMAGNETIC • Magnetic Induction on phi bond causes the formation of pi bonds • The presence of phi bond (double bond) or phi system will affect the chemical shift of nearby proton • Accured on alkyne, alkene and benzene ring

  28. - ALKYNE

  29. - ALKENE

  30. - BENZENE RING

  31. SPLITTING SIGNAL • On NMR spectrum, proton signals often do not appear as a single peak (singlet), but appear as doublet, triplet, quartet, and so on • Spin-spin splitting on ​​the H atom is due to the interaction (coupling) with the neighboring H atom • Spin-spin splitting followed the (n +1) RULES, if an Atom H has n non-equivalent H atoms which are neighbors, then the NMR spectrum of H atom signal will experience a breakdown as a (n +1) peaks

  32. (n+1) RULES n = 1, the signal will be splitted as (1+1) peaks, doublet n = 3, the signal will be splitted as (3+1) peaks, quartet

  33. EXCEPTIONAL FOR (n+1) RULES Equivalent protons due to symmetry effects are usually not mutually spliting each other 1) no splitting if x=y no splitting if x=y Protons in the same group (tied to the same C) are usually not mutually splitting each other 2) or

  34. EXEPTIONAL FOR (n+1) RULES N +1 rule applied to the protons in the aliphatic chain (saturated) or cyclic saturated. 3) or YES YES But it is not applied to the protons of the double bond or benzene compounds NO NO

  35. PASCAL TRIANGLE • Splitting pattern similar with PASCAL TRIANGLE rule

  36. SPLITTING PATTERN ( x = y ) ( x = y )

  37. SPLITTING

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