Nuclear Magnetic Resonance (NMR) Spectroscopy is a non-destructive analytical technique that is used to probe the nature and characteristics of molecular structure.

1. NUCLEAR MAGNETIC
RESONANCE (NMR)
PRESENTED BY: GULSHAN KUMAR
GUIDE: Dr ANJOO KAMBOJ
ROLL NO. :CCP232020 M.PHARM (1ST SEM)
MODREN PHARMACUTICAL ANALYSIS TECHNIQUES

2. CONTENT
 History
 Introduction
 Theory
 Principle
 NMR Spectra
 NMR Instrumentation
 Chemical Shift
 Factor Affecting Chemical Shift
 Proton NMR
 N+1 Rule, Spin-Spin Coupling
 Rules of Spin-Spin Coupling
 Application of NMR
 Application of NMR in Medicines

4. INTRODUCTION
Nuclear Magnetic Resonance Spectroscopy, most commonly
known as NMR spectroscopy.
Based upon the absorption of electromagnetic radiation in the
radio frequency region 4 to 900 MHz by nuclei of the atoms.
• Proton Nuclear magnetic resonance spectroscopy is one of
most powerful tools for elucidating the number of hydrogen
or proton in the compound.
• Spectroscopy determines the physical and chemical
properties of atoms or the molecules in which they are
contained and provide detailed information about the
structure, dynamics, reaction state, and chemical environment
of molecules.
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5. It is used to study a wide variety of nuclei:
• 1H
• 15N
• 19F
• 13C
• 31P
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6. THEORY OF NMR
Spin quantum number (I) is related to the atomic and mass number of the nucleus
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I Z A E.g.;
Half integer Odd Odd 1H (1/2)
Half integer Odd Even 13C (1/2)
Integer Even Odd 2H (1)
Zero Even Even 12C (0)

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9. Elements with either odd mass or odd atomic number have the property of nuclear
“spin”.
If an external ,magnetic field is applied, the number of possible orientation calculated by
(2I+1).
E.g.; Hydrogen has spin quantum number I= ½ and possible orientation is (2*1/2+1=2)
two, i.e., +1/2 and -1/2.
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12. PRINCIPLE
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o The principle is based on the spinning of nucleus and generating a
magnetic field.
o Without external magnetic (Bo)-field nuclear spin are random in
direction.
o With Bo, nuclei align themselves either with or against field of
external magnetic field.
o If an external magnetic field is applied an energy transfer (ΔE) is
possible between ground state to excited state.
o When the spin returns to its ground state level, the absorbed
radiofrequency energy is emitted at the same level.
o The emitted radiofrequency signal that give the NMR spectrum of
the concerned nucleus.
o The emitted radio frequency is directly proportional to the strength
of the applied field.
v=
γ𝐵𝑜
2Π
Bo= EMF experienced by proton γ= Magnetogyric ratio

13. NMR SPECTRA
The NMR spectrum is a plot of intensity of NMR signals VS
magnetic field (frequency) in reference to TMS.
Reasons for taking TMS as reference Standard:
1. Chemically inert, magnetically isotopic, volatile & soluble in
most organic solvents.
2. TMS gives an intense signal.
3. TMS can be easily removed.
4. Electro negativity is low.
5 It doesn't make any intermolecular association with sample
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14. NMR INSTRUMENTATION
1. Sample tube/sample holder
2. Permanent magnet
3. Magnet coil
4. Sweep generator
5. Radio frequency transmitter
(Radio frequency input oscillator)
6. Radio frequency reviver
7. Read out system
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15. Sample tube/sample holder
It should be chemically inert, durable & transparent to NMR radiation.
Generally about 8.5 cm long & approximately 0.3 cm in diameter is employed.
Sample probe
It's the device that hold sample tube in position & is provided with an air drive for rotating the sample tube almost 100
revolutions per min.
Permanent Magnet
It provide homogenous magnetic field at 60-100MHz
Magnetic coil
It induce magnetic field when current flow through them
Sweep generator
To produce equal amount of magnetic field pass through the sample
Radio frequency transmitter
Transmitter is fed on to a pair of coils mounted on right angles to the path of field. 60 MHz capacity is normally used.
Radio frequency receiver
detect radio frequencies emitted as nuclei relax at lower energy level
Signal detector & recording system
The electrical signal generated is amplified by means of amplifier & then recorded.
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16. CHEMICAL SHIFT
A chemical shift is defined as the difference in parts per million (ppm) between the resonance frequency of the observed proton
and tetramethyl silane (TMS) hydrogens.
TMS is the most common reference compound in NMR, it is set at δ=0 ppm
Shielding of protons:-
High electron density around a nucleus shields the nucleus from the external magnetic field and the signals are up field in the
NMR spectrum
DE shielding of protons:-
Lower electron density around a nucleus Deshields the nucleus from the external magnetic field and the signals are downfield in
the NMR spectrum
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17. FACTORS AFFECTING CHEMICAL SHIFT
o Electronegative groups/ Inductive effect
o Magnetic anisotropy of Π-systems/diamagnetic effect of pi bond
o Hydrogen bonding
o Vander Waal's DE shielding
o Effect of temperature &Effect of solvent
Electronegative groups:-
Electronegative groups attached to the C-H system decrease the electron
density around the protons, and there is less shielding (i.e.DE shielding) and
chemical shift increases
Magnetic anisotropy of T-systems-( space effect)
So magnetic anisotropy means that there is a "non-uniform magnetic field".
✓ Electrons in IT systems (e.g. aromatics, alkenes, alkynes, carbonyls etc.)
interact with the applied field which induces a magnetic field that causes the
anisotropy.
✓ It causes both shielding and de-shielding of protons. Example:-Benzene
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18. Vander Waal's DE shielding
✔The electron cloud of a bulkier group will tend to repel the
electron cloud surrounding the proton.
✓ such a proton will be DE shielded & will resonate at slightly
higher value of 8 than expected in the absence of this effect.
Effect of temperature
Resonance position of most signals is little affected by temperature.
Effect of solvent
Chemical shift change when the solvent changed from CCI, to
CDCI, is 0.1 ppm. But change to more polar solvents like
methanol, the change is 0.3 ppm. Solvents used in NMRCCI, CS2,
CDCE, C.D., D:0
Hydrogen bonding
✓ Protons that are involved in hydrogen bonding are typically
change the chemical shift values.
✓ The more hydrogen bonding, the more proton is DE shielded and
chemical shift value is higher.
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19. PROTON NMR
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The most common for of NMR is based on the
hydrogen-1 (1H), nucleus or proton. It can give
information about the structure of any molecule
containing hydrogen atoms.
E.g., ethanol3 types of:-CH2,CH3,OH
Interpretation of 1HNMR spectra:-
Number of signals
Position of signals
Relative intensity of signals
Splitting of signals (spin-spin coupling)
- Indicates how many "different kinds" of protons are
present.
- Indicates something about (chemical shift) magnetic
(electronic) environment of protons
-Proportional to number of protons present signals
- Indicates the number of nearby nuclei usually protons"

20. n+1 rule
• The multiplicity of signal is calculated by using n+1
rule.
• This is one of the rule to predict the splitting of proton
signals.
This is considered by the nearby hydrogen nuclei.
Therefore, n= Number of protons in nearby nuclei
 Zero H atom as neighbour n+1-0+1=1(singlet)
 One H atom as neighbour n+1=1+1=2(doublet)
 Two H atom as neighbour n+1=2+1=3(triplet)
Spin-spin coupling (splitting)
The interaction between the spins of neighbouring
nuclei in a molecule may cause the splitting of NMR
spectrum.
The splitting pattern is related to the number of
equivalent H- atom at the nearby nuclei.
E.g.., Ethyl acetate
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21. RULES OF SPIN-SPIN COUPLING
Chemically equivalent protons do not show spin-spin coupling &Only
nonequivalent protons couple.
Hs couples with He
Hb & Ha do not couple because they are equivalent
He & Hd do not couple because they are equivalent
Protons on adjacent carbons normally will couple.
Protons separated by four or more bonds will not couple.
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22. ORIGINS OF SIGNAL SPLITTING
The origins of signal splitting patterns in which, each arrow
represents an Hь nuclear spin orientation.
COUPLING CONSTANT (J-Hz)
Measurement of splitting effect is based on the distance
between the peak in a given multiplet. Useful in 1H NMR of
complex structure
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23. APPLICATIONS OF NMR
Nuclear Magnetic Resonance (NMR) Spectroscopy is a non-destructive analytical technique that is used to probe
the nature and characteristics of molecular structure. A simple NMR experiment produces information in the form
of a spectrum, which is able to provide details about:
• The types of atoms present in the sample
• The relative amounts of atoms present in a sample
• The specific environments of atoms within a molecule
⚫ The purity and composition of a sample• Structural information about a molecule, including constitutional and
conformational isomerization
Hydrogen bonding
• Drug screening and design
Particularly useful for identifying drug leads and determining the conformations of the compounds bound to
enzymes, receptors, and other proteins.
• Native membrane protein
Solid state NMR has the potential for determining atomic-resolution structures of domains of membrane proteins
in their native membrane environments, including those with bound ligands
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24. CONT..
Metabolite analysis
A very powerful technology for metabolite analysis.
Chemical analysis
A matured technique for chemical identification and conformational analysis of chemicals whether
synthetic or natural.
✓ NMR is used in biology to study the Biofluids, Cells, Perfused organs and biomacromolecules such as Nucleic
acids(DNA, RNA), carbohydrates Proteins and peptides. And also studies in biochemistry.
Labelling NMR is used in physics and physical chemistry to study High pressure Diffusion, Liquid crystals, liquid
Crystal solutions, Membranes, Rigid solids.
✓ NMR is used in food science.
'H-NMR SPECTROSCOPY applications
'H widely used for structure elucidation.
Inorganic solids- In organic compounds are investigated by solid state 1H-NMR.eg CaSO4-H2O.
Organic solids- Solid-state 'H NMR constitutes a powerful approach to investigate the hydrogen-bonding and
ionization states of small organic compounds.
• Direct correlation with hydrogen-bonding lengths could be demonstrated, e.g. for amino acid carboxyl groups.
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25. APPLICATION OF NMR IN MEDICINES
MRI is specialist application of multi dimensional Fourier transformation NMR
Anatomical imaging Measuring physiological functions
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26. CONT..
Flow measurements and angiography. Tissue perfusion studies.
TUMORS
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27. THANK YOU
Gulshan kumar Roll no.: ccp232020
m. Pharm (sem 1st)