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1. MET FACULTY OF PHARMACY
PRESENTATION ON NUCLEAR MAGNETIC RESONANACE
SUBMITTED BY:
ANSHIKA BHATNAGAR
M.PHARMA FIRST YEAR
(PHARMACEUTICAL CHEMISTRY)

2. TABLE OF CONTENT:
 Introduction
 Principle of Nuclear Magnetic Resonance
 Quantum number and their rules in NMR
 Instrumentation of NMR
 Solvent requirement in NMR
 Relaxation Process
 NMR signals in Various compounds
 Chemical shift and Factors influencing chemical shift
 Spin -Spin coupling
 Coupling constant

3. INTRODUCTION
 Nuclear magnetic resonance (NMR) spectrometry is another form of Absorption
spectrometry in which radio frequency waves induce transitions between magnetic
energy levels of nuclei of a molecule.
 All nuclei carry a charge. In some nuclei this charge spins on the nuclear axis and this
circulation of nuclear charge generates a magnetic dipole along the axis.
 The angular momentum of the spinning charge can be described in terms of quantum
spin numbers.
 Radio waves are the lowest energy form of electromagnetic radiation and it can be seen
that the quantity of energy involved in rf radiation is very small which is too small to
vibrate, rotate or excite an atom or molecule. But this energy is sufficient to affect the
nuclear spin of the atom of a molecule.

4. PRINCIPLE OF NMR
The above figure showing the nucleus in Absence and Presence of External
Magnatic field

5. CONTINUE
 NMR is based on the spins of atomic nuclei.
 Two possible orientation means nucleus can either aligned with the applied magnetic field or
aligned against the field.
 If an external magnetic field is applied, an energy transfer is possible between ground state to
excited state.
 When the spin returns to its ground state level, the absorbed radiofrequency energy is emitted
at the same frequency level.
 The emitted radiofrequency signal that give the NMR spectrum of the concerned nucleus.

6. CONTINUE
 The emitted radio frequency is directly proportional to the strength of
the applied field.

7. QUANTUM NUMBERS AND THEIR RULES IN NMR
 All nuclei carry a charge and some nuclei spins on the nuclear axis.
 This spinning of nuclear charge generates a magnetic dipole along the axis.
 The angular momentum of the spinning charge i.e. spinning nucleus can be describe in terms of
Quantum spin number.
 Spin number “I” can have value of 0,1/2, 1, 3/2 and so on.
 I=0 denotes no spin .

8. CONT.

9. INSTRUMENTATION OF NMR

10. COMPONENTS OF INSTRUMENT DESCRIPTION
A. Sample holder  It should be chemically inert, durable and transparent to rf
radiation. It is generally about 8.5 cm long and 0.3 cm in diameter.
B. Permanent Magnet  Important feature of the magnet is that it should give
homogeneous magnetic field.
 The strength of the field should be very high i.e., at least 20,000
Gauss, because the chemical shifts are proportional to the field
strength.
 It is also important that the magnetic field be constant over long
period of time . For this reason adequate temperature control is
necessary to maintain the constant physical dimensions of the
magnet.
C. Magnetic coils  There is a relation between the resonance frequency of the
nucleus and the strength of the magnetic field in which the
sample is placed. This relationship is expressed by equation :
υ = Constant X H0
Where υ = Resonance frequency of Nucleus, H0 = Strength of magnetic field.

11. D. Sweep Generator  To produce the equal amount of magnetic field pass through
the sample.
E, Radio Frequency Transmitter  A radio transmitter coil that produces a short powerful pulse of
radio waves.
F. Radio Frequency Receiver  A radio receiver coil that detects radio frequencies emitted as nuclei
relax to a lower energy level.
G. Readout system  A computer that analyses and record the data.

12. SOLVENT REQUIREMENT IN NMR
 The sample cannot be obtained in the pure state so in that case it is necessary to dissolve it or
extract it from some other medium.
 Characteristics of a good solvent is given below:
1. It should be chemically inert towards the sample.
2. It should be easily recoverable if the original sample is required after examination.
3. Solvents containing no hydrogen in the molecule.
Examples of solvent used in NMR:
Carbon tetrachloride(CCl4) , carbon disulfide(CS2), Deuteriochloroform (CDCl3 HexadeuterioBenzene
(C6D6, Deuterium oxide (D2O)
Note: The deuterium nucleus does not respond, in the same region as the hydrogen nucleus .
Substitution of D to H provides elimination of unwanted H signals.

13. RELAXATION PROCESS:

14. CHEMICAL SHIFT
 The shifts in the position of NMR signal (Compared with a standard reference) resulting from the
shielding and deshielding by electrons are referred as chemical shift.