NMR spectroscopy involves applying a magnetic field to atomic nuclei and observing the energy absorbed as nuclei transition between spin states. Key developments include Bloch and Purcell observing NMR in bulk samples in 1946, Ernst and Anderson introducing Fourier transform NMR in 1966, and Wüthrich determining the first protein structure from NMR data in 1985. NMR instruments consist of a strong magnet, RF generator and transmitter/receiver coils to apply electromagnetic pulses and detect the absorbed energy. Samples are dissolved in deuterated solvents to avoid interference from solvent proton signals. Spectra are analyzed based on chemical shifts and peak splitting patterns that provide structural information.

1. Dr. Hari Singh Gour University, Sagar
Department of Physics
Submitted By:
Praveen Kumar Litoriya
Registration no.- Y-16273028 1
Nuclear Magnetic Resonance
Spectroscopy

2. NMR is
abbreviation of
Nuclear
Magnetic
Resonance

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NMR History
1937 Rabi predicts and observes nuclear magnetic resonance
1946 Bloch, Purcell first nuclear magnetic resonance of bulk sample
1953 Overhauser NOE (nuclear Overhauser effect)
1966 Ernst, Anderson Fourier transform NMR
1975 Jeener, Ernst 2D NMR
1985 Wüthrich first solution structure of a small protein (BPTI)
from NOE derived distance restraints
1987 3D NMR + 13C, 15N isotope labeling of recombinant proteins
(resolution)
1990 pulsed field gradients (artifact suppression)
1996/7 new long range structural parameters:
- residual dipolar couplings from partial alignment in liquid
crystalline media
Nobel prizes
1944 Physics Rabi (Columbia)
1952 Physics Bloch (Stanford), Purcell (Harvard)
1991 Chemistry Ernst (ETH)
2002 Chemistry Wüthrich (ETH)
2003 Medicine Lauterbur (University of Illinois in Urbana ),
Mansfield (University of Nottingham)

4. NMR spectroscopy is a form of absorption spectrometry.
NMR Spectroscopy
Most absorption techniques (e.g. – Ultraviolet-Visible and
Infrared) involve the electrons… in the case of NMR, it is
the nucleus of the atom which determines the response.
An applied (magnetic) field is necessary to “develop” the
energy states (produce a separation of the energy states)
necessary for the absorption to occur.

5. The most important parts of an NMR instrument are:
• The magnet,
• The RF generator,
• The sample chamber or probe,
• (which not only houses the sample but also the RF
transmission and detection coils).
• In addition, the instrument requires:
• A pulse generator
• An RF receiver,
• Lots of electronics, and a computer for data processing
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6. NMR Schematic Diagram
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Magnet Legs
NMR Magnet Cross-Section

8. Primitive NMR Spectrometer

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When an external magnetic field is applied, hydrogen
nuclei can align with the external field or against it
∆E radio waves
External
magnetic
field
Nucleus aligned with
magnetic field –
low-energy state.
Nucleus aligned
opposed to magnetic
field – high-energy
state.
• As nuclei relax back to the low-energy alignment, energy in the
radio wave frequency is released. This energy is detected and
recorded as peaks on a spectrum.
Energy Differentiation

10. Bo = 0 Bo > 0
Randomly oriented Highly oriented
Bo
Ensemble of Nuclear Spins
N
S
Each nucleus behaves like
a bar magnet.

11. Bo = 0 Bo > 0
E DE
Allowed Energy States for a
Spin 1/2 System
antiparallel
parallel
DE = g h Bo = h n
-1/2
+1/2
Therefore, the nuclei will absorb light with energy DE resulting
in a change of the spin states.

12. Preparing a sample
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• To obtain the 1H NMR spectrum of a sample it is
usually necessary to dissolve the sample in a
solvent.
• Solvents must not contain protons that will
interfere with the sample being measured.
• A solvent must:
– contain no hydrogen atoms, eg tetrachloromethane,
CCl4
or
– have the hydrogen atoms replaced with deuterium
(2H), eg CDCl3 or CD3OD.

13. Explaining spectra
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The scale runs from right to
left and is called the
chemical shift. It is
measured in parts per
million (ppm). Peaks to the
left of TMS peak are said to
be downfield of TMS.
TMS (tetramethylsilane)
is added to the solvent
and provides a reference
peak. The protons in
TMS are assigned the
value
0 ppm and the rest of the
spectrum is calibrated
relative to this.

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Example 1
Methyl ethanoate
C O C
O
C
H
H
H H
H
H

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n + 1 rule
• The number of peaks in a multiplet can give
additional information about the structure.
• The splitting of peaks is caused by the
neighbouring carbon’s hydrogen atoms.
• Protons in the same environment are said to be
equivalent and as such behave as one proton.
• This follows the n + 1 rule.
– n is the number of hydrogen atoms attached to the
next-door carbon
– n + 1 is how many peaks will be seen in the cluster.

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Example 2 – Assign the peaks and suggest a structure
Molecular formula C3H7Br
C C
H
H H
H
C
H
H
H
Br
CH3
A triplet due
to CH2 group
adjacent.
CH2This is not a simple
quartet. There are
extra splittings due to
CH3 and CH2
neighbouring groups.
CH2
A triplet
due to
CH2
group
adjacent.

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Application
MRI is the best
medical
application for
imaging, it is
working on
same principal
as Nuclear
Magnetic
Resonance.

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Solid State NMR for studying Nuclear waste
glass
• Vitrification of high level nuclear wastes (HLW) is an important step
for storing nuclear waste
• Vast experiences gathered from these investigations have identified
sodium borosilicate glasses as one of the most promising inert host
matrices

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