1. NMR Spectroscopy Dr. PALVE ANIL M. RAYAT SHIKSHAN SANSTHA’S
M.P.A.S.C.COLLEGE,PANVEL,NAVI MUMBAI.

2. !!! WHAT TO DO !!!! HOW TO THINK?????

3. A.M.Palve

4.   = wavelength distance Electromagnetic radiation consists of
perpendicular oscillating electric and
magnetic fields 
 = wavelength
distance

5. h = Planck's Constant 6.62 10-27 erg - sec
(The energy of photon) E = h
 = c/
E = hc/
E = hύ
h = Planck's Constant 6.62 erg - sec
c = the speed of light
in vacuum c = 3.00 x 108 m/s
The wavelength of light determines how it interacts with matter.
We use these interactions as a probe to obtain structural information about samples.

6. Matter/Energy Interactions
What happens when a sample absorbs IR energy?
stretching and bending of bonds
(typically covalent bonds)
Evibration increases momentarily IR
-O-H -O —H
(3500 cm-1)
opposed
to field
What happens when a sample absorbs Rf energy (radio frequencies) in an NMR experiment?
nuclei previously aligned in a strong external magnetic field are “flipped” against the field Rf
(100’s MHz)
aligned
with field
{B0 = external magnetic field}
 B0

7. Felix Bloch
Stanford Univ
Edward Purcell
Harvard Univ
Ernst
Wüthrich
ETH Switzerland
Paul Lauterbur
Illinois Univ, USA

8. Nuclear Magnetic Resonance Spectroscopy
• Nuclei aligned in a strong magnetic field can be selectively
detected by subjecting a sample to radio frequency energies.
• 1H-NMR Spectroscopy  detailed structural evidence for organic
samples indicated by the number and types of hydrogens detected.
1. NMR theory - nuclear spin, electron shielding
2. acquisition of data - the NMR spectrometer
3. interpretation of NMR spectral data {major emphasis!}

9. Properties of Nuclei At. No. Spin number Nucleus odd ½,1,2/3 11H √
Mass No.
At. No.
Spin number
Nucleus
odd
Even/odd
½,1,2/3
11H √
Even
1212C X
1,2,3
147N

10. Spectrometer
300 MHz

11. 400 MHz NMR Spectrometer 400 MHz Avance System Unix computer
electronic
controls
super-
conducting
magnet

12. NMR Sample Position (prior to release into probe)
positioned
at top of probe
Liquid Nitrogen
-196°C (77.4 K)
Liquid Helium
-269°C (4.2 K)
Superconducting magnets
require continuous cooling.

14. Chemical Shift

16. Less energy to flip nucleus
More energy to flip nucleus
d, ppm
chemical shift

17. Chemical Shift

18. Chemical Equivalence
Protons in chemically identical environments within a molecule
Often exhibit same chemical shift

19. Chemical Nonequivalence
Sets of protons in chemically different environments within a molecule
Give rise to different chemical shifts

20. Basic Information from 1H NMR Spectra
Number of Signals – No. of different types of protons.
Chemical Shifts – Type of environment for protons.
Integration – Ratios of numbers of protons.
Signal shape – Dynamics of proton environments.
Signal splitting – No. and geometry of nearby protons.

21. Ideal Solvent No protons deuterated solvents used Inert solvent
Low boiling
Inexpensive
Nonviscous

22. Chemical Shifts of Deuterated Solvents
Acetone-d6
2.04(5)
CDCl3
7.26(s)
DMSO- d6
2.49(5)
CH3CN- d3
1.93(5)
D2O
4.82(s)
CH3OH-d4
4.84(1)
3.30(5)
CH2Cl2-d2
5.32(3)

23. TMS (tetramethylsilane)
Internal standard
TMS (tetramethylsilane)
Protons of methyl group more shielded
Gives single, sharp absorption peak
Chemically inert solvent
Symmetrical
Volatile (B.P. 27°C)
Soluble in most organic solvents

24. Magnetic Anisotropy

25. Vinylic
C=C-H
ppm
Acetylenic
2-3ppm
Aromatic
Ar-H
6-8.5ppm
Aldehydic
R-CHO
9-10ppm

26. 1H-NMR - Correlation Diagram
common
singlets
Chloroform (CHCl3) = 7.26 d 
Benzene (C6H6) = 7.32 d 
Methylene chloride
(CH2Cl2) = 5.30 d 
Acetone (CH3COCH3) = 2.16 d 
Toluene (C6H6CH3) = 2.32 d 
TMS
0.00 d 
type of
attachment
Protons Attached to sp2 Carbon
Protons Attached to sp3 Carbon
RCH2OR
RCH2NR2
ArCH3 RCOCH3
R3CH methine
R2CH2 methylene
RCH3 methyl
Vinyl
R2C=CHR
RCH2X
X = F, Cl, Br, I
RCHO
Aromatic ArH
Delta
Scale
(d)
even more
deshielded
deshielded
shielded
due to:
due to:
ring currents (from p bonds)
inductive effect (through s bonds)