Methods of pharmaceutucal research- NMR M pharma 2nd send' dr harisingh gour sagar university

1. Basics of NMR
Spectroscopy

2. BASIC THEORETICAL BACKGROUND OF NMR
SPECTROSCOPY
Assignment of
METHODS IN PHARMACEUTICAL RESEARCH (MPR)
PHS CC 1201
Session 2023-2024
Department of Pharmaceutical Sciences
Dr. HarisinghGour Vishwavidyalaya,Sagar, (M.P.)
(A Central University)
Supervisors:
PROF. ASMITAGAJBHIYE
DR. UDITA AGRAWAL
MR.SHIVAM KORI
MR.DEEPAK DWIVEDI
Submitted by:
ADARSH SHARMA
Y23254001

3. ACKNOWLEGEMENT
• I sincerely appreciate the assistance and support I received from my guide and other faculty
members during my assignment PROF. ASMITA GAJBHIYE MAM, DR.UDITA
AGRAWAL MAM, MR.SHIVAM KORI SIR AND MR. DEEPAK DWIVEDI SIR.

4. Contents:
1. INTRODUCTION
2. ABOUT NUCLEAR MAGNETIC RESONANCE(NMR)
3. PRINCIPLE
4.NMR SPECTRUM
5. INSTRUMENTATION
6.SOLVENT USED AND CHEMICAL SHIFT

5.  What is Spectroscopy?
The study of Electromagnetic Radiations (EMR) with matter, which may result in
Absorption
Transmission
Reflection
Emission
• The molecules, atoms, ions of sample move from one energy state to another energy state.
• Change can be from ground state to excited state or vice-versa.
• At ground state, energies are sum total of rotational, vibrational, electronic energies.

6.  NMR Spectroscopy is a spectroscopic technique which is based on absorption of
electromagnetic radiation in radio frequency region 4-900 MHz by nuclei of atoms.
 It is basically study of spin changes at the nuclear level when a radiofrequency is absorbed in
presence of magnetic field.
 When proton(Hydrogen) is studied, then it is called as Proton Magnetic Resonance(PMR).
 It is one the most powerful tool in elucidating the number of hydrogen or proton in compound.
 Other nuclei studied are:
13C 19F
35Cl 31P

7.  Nuclei with odd mass number only gives NMR Spectra like 1H, 13C,
35Cl because they have asymmetrical charge distribution
 Spin quantum number for such nuclei will be 1/2, 3/2, 5/2 etc.
 For 1H, it is 1/2.
 Other nuclei like 12C,16O, 14N, do not give NMR spectra because of
symmetrical charge distribution and their spin quantum is integral
value.
• The Spin Quantum Number
describes the angular
momentum of an electron.
• An electron spins around an
axis and has both angular
momentum and orbital angular
momentum.
• Because angular momentum is
a vector, the Spin Quantum
Number has both a magnitude
(1/2) and direction (+ or -).
I Atomic
Mass
Atomic
Number
Examples
Half-
Integer
Odd Odd 1H
Half-
Integer
Odd Even 13C
Integer Even Odd 2H
Zero Even Even 12C
 Elements with odd mass or odd atomic number have property of nuclear spin.

8. Any proton or nucleus with odd mass number spins on
its own axis.
By application of an external magnetic field, the nucleus
spins on its own axis, creating a magnetic field resulting
in a precessional orbit with precessional frequency.
This state is called Ground state or Parallel Orientation.
The magnetic field caused by spin of nuclei is aligned
with the externally applied magnetic field.
Radiofrequency is applied, and when
Applied frequency = Precessional frequency, absorption of
energy occurs, and NMR signal is recorded.
Because of absorption of energy, the nucleus moves
from ground state to excited state, results in Spin
Reversal(Anti-Parallel Orientation).

10. The NMR Spectrum is plot of intensity of NMR Signals
vs Magnetic Fields (Frequency) in reference to TMS.
 Tetramethylsilane (TMS) – internal reference compound
for 1H NMR.
 It has a strong, sharp resonance line from its 12 protons,
with a chemical shift at low resonance frequency relative
to almost all other 1H resonances.

11. 1.) Sample
Holder
Glass tubes with 8.5cm
long; 0.3cm in diameter
2.) RF
Transmitter
Used to apply
radiofrequency
3.)RF
Receiver/
Detector
To measure intensity of
radiofrequencies emitted
4.)Permanen
t Magnets
Provides homogenous
magnetic field 60-100MHz
5.)Magnetic
Coils
Induces magnetic fields
when current flows
through it
6.)Sweep
Generator
To vary strength of applied
magnetic fields ;to sweep
magnetic field
7.)Recorder To record NMR Signal
obtained

12. 1.) CCl4- Carbon Tetrachloride
2.) CS2 – Carbon Disulfide
3.) CDCl3 - Deuteriocholoform
4.) C6D6 – Hexa Deuteriobenzene
5.) D2O – Deuterium Oxide
 As we are analysing organic compounds for the nature, type, number and
environment of Protons(Hydrogen), the solvent used in NMR spectroscopy
should not contain Hydrogen atoms.
 Hydrogen is replaced by Deuterium.
PROPERTIES OF SOLVENT:
1.) Chemical inertness
2.) Magnetic isotropy (magnetically neutral)
3.) Volatility
4.) Absence of Hydrogen atoms
5.) Easily available and Inexpensive

13. 1.) Shielding of
protons
• High electron density around a nucleus shields the nucleus from external
magnetic field and the signals are upfield in NMR Spectrum.
• Closer to electropositive atom.
• More magnetic field required for excitation.
1.) Deshielding of
protons
• Low electron density around a nucleus deshields the nucleus from external
magnetic field and the signals are downfield in NMR Spectrum.
• Closer to electronegative atom.
• Less magnetic field required for excitation.

14. • Theoretically for any organic compound, for all
protons present only NMR signal should be
recorded.
• But this does not happen in practice since all
hydrogen atoms are not in same environment
i.e. magnetic field applied is not felt by all
hydrogen atoms uniformly.
• This happens due to presence of double and
triple bonds; or aromatic, alicyclic ring system
or electronegative atoms.
• Chemical shift is the difference between the
absorption position of sample proton and the
absorption position of reference compound.
• Chemical shift is measured in Ϩ values.
• The value ranges from 0 to 10 Ϩ for most of the
compounds.
• TMS is most common reference compound set
to Ϩ=0ppm.
FACTORS AFFECTING CHEMICAL SHIFT:
1.) Electronegative groups: leads to deshielding, increasing
chemical shift
2.) Magnetic anisotropy: non uniform magnetic field.
Electrons in pie(carbonyls, alkenes, aromatic) systems
interact with applied magnetic field which induces
magnetic field causing anisotropy.
- causes shielding and deshielding of protons
3.) Hydrogen bonding: More the Hydrogen bonding,
more is the deshielding , chemical shift higher.

16. References:
1.) Pavia D, Lampman G, Kriz G, Vyvyan J, "Introduction to Spectroscopy", Cengage Learning, 5th
edition, 2013, Pg no: 215-255
2.) Shankar S, " Textbook of Pharmaceutical Analysis", Rx Publications , 5th edition, 2018, Pg no:
6-1: 6-9
3.) Chatwal G, Anand S, “ Instrumental methods of chemical analysis”, Himalaya publishing house,
2019, Pg no: 2.185-2.234
4.) Silverstein, R. M., F. X. Webster and D. J. Kiemle, Spectrometric Identification of Organic
Compounds, 7th ed., John Wiley and Sons, 2005, Pg no: 500-550
5. Friebolin, H., Basic One- and Two-Dimensional NMR Spectroscopy, 5th ed., Wiley-VCH
Publishers, New York, 2010