basics of NMR and its applications

1. BY : E.SIVANAGI REDDY

2. NMR Nobel Prize Laureates
Otto Stern (1943) Isidor I. Rabi(1944)
Richard Ernst (1990 c) Kurt Wüthrich ( 2002c) Paul C. Lauterbur , Sir Peter
Mansfield (2003M)

3. Out line of presentation
 Introduction
 Birth of NMR
 Principle of NMR
 Types of Nuclei
 NMR Spectroscopy
 Applications
 Summary
 References

4. Introduction
 NMR –a technique for determining the magnetic
moments of nuclei by subjecting a substance to high-
frequency radiation and a large magnetic field.
 NMR =
 Nuclear: properties of atomic nuclei
 Magnetic: magnetic field is required
 Resonance: interaction between
magnetic field and radio frequency

5. Birth of NMR
 1945 – Purcell, Torrey, and Pound
(Harvard, Cambridge, Massachusetts) detected weak
radio- frequency signals generated by the nuclei of atoms
in about 1 kg of paraffin wax placed in a magnetic field.
 Simultaneously, Bloch, Hansen, and Packard
(Stanford, Palo Alto, California) independently observed
radio signals from atomic nuclei in water in a magnetic
field.
E. M. Purcell, H.C. Torrey, and R.V. Pound, Phys. Rev., 1946, V69, p.37
F. Bloch, W.W. Hansen, and M.E. Packard, Phys. Rev., 1946, V69, p.127

6. Birth of NMR
 Purcell, Torrey, and Pound described NMR as
observation of absorption by the nuclear spin system
that produces an additional load that changes the
quality factor Q of the circuit that drives the
resonance.
 Bloch, Hansen, and Packard described NMR as forced
precession of the nuclear magnetization in the applied
radio frequency field and the induction of detectable
electromotive force in a receiver coil .

7. Principle of Magnetic Resonance
 When molecules are placed in a strong magnetic
field , the magnetic moments of the nuclei align with
the field
 This equilibrium alignment can be changed to an
excited state by applying radio frequency(RF) pulses
 When the nuclei revert to the equilibrium ,they emit
RF radiation that can be detected.

8. The NMR Phenomenon
1. A spinning charge generates In the presence of an external magnetic field
a magnetic field (B0), two spin states exist, +1/2 and -1/2.

9. Nuclear magnetic Resonance
When oriented nuclei are subjected to E.M radiation at the proper
frequency
Energy absorption occurs
 Lower energy state nuclei “Spin-flip ” to the higher energy state
 Magnetic nuclei in resonance with applied field

10. Nuclear magnetic Resonance
 Resonant frequency depends on strength of magnetic
field and identity of nucleus.

11. Types of Nuclei
 Chemistry: 1H, 13C
 Bio-sciences: 1H, 13C, 15N, 19F, 31P, etc.
 Medicine: 1H, 17O

12. Nuclear Magnetic resonance Spectroscopy

13. NMR Spectrometer

14. Protons in a Molecule
 Depending on their chemical environment, protons in
a molecule are shielded by different amounts

15.  Number different kinds of protons
 location shielded or dishielded
 intensity number of protons of that type
 splitting number of protons on adjacent
atoms

16. Chemical shift
 Chemical shift is a measure of the degree to
which a nucleus in a molecule is shielded
Factors affecting
 Electronegativity of nearby atoms
• Hybridization of adjacent atoms
• diamagnetic effects
• paramagnetic effects
• solvent effect

17. Standard for Chemical Shift
 In NMR spectroscopy, the standard is often tetramethylsilane,
Si(CH3)4, abbreviated TMS
 Tetramethyl silane (TMS) is used as reference because
it is soluble in most organic solvents, is inert, volatile, and
has 12 equivalent 1H and 4 equivalent 13C. TMS signal is
set to 0 .

18. shielding

19. J

21. Applications of NMR
CHEMISTRY
 Determine molecular structure of different chemical
compounds, including polymers
 Identify products of chemical reactions
 Means to study dynamics, kinetics, and
thermodynamics of chemical systems
BIOLOGY
 Protein NMR
– Obtain structural information on complex proteins
– Multidimensional experiments needed to correlate
frequencies with distinct nuclei

22. Applications of NMR
MEDICINE
Magnetic Resonance Imaging (MRI)
– Insight into the structure of the human body
– Sharp contrast in soft tissue
Clinical applications
– Cardiovascular system
– Musculoskeletal system
– Oncology
– Neurology

23. Summary
 Nuclear Magnetic Resonance (NMR): change in
alignment of atomic nuclei from preferred energy
states due to intrinsic magnetic properties
 Used to determine structural framework of chemical
compounds
 Applicable for multiple disciplines
– Medicine
–Chemistry
– Biology

24. REFERENCES
 James Keeler ,Understanding NMR Spectroscopy,
Wiley International (2002)
 James N. Shoolery , A Basic Guide to NMR, Varian
Associates, Palo Alto, CA, USA, 1972
 J. Jon and H. S. Gutowsk, NMR IN CHEMISTRY
-AN EVERGREEN ,Ann. Re. Phys. Cher 1980.
31:1-27

25. NMR: Nobel work if
you can get it