principle of NMR spectroscopy and working of NMR is givven in that slides

1. PRINCIPLE AND WORKING OF NMR
SPECTROSCOPY
Presented by,
Prof. Pramod V.Burakale
Dept. of P’ceutical chemistry
IBSS,College of pharmacy
Malkapur.
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2. CONTENTS
 Introduction
 Basics of atomic structure
 Spin quantum No.
 What is NMR?
 Precessional frequency & motion
 Theory of NMR
 Larmor equation
 Instrumentation
 Types of NMR
 Advantages of FT-NMR
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3. INTRODUCTION
 NMR is the most powerful tool available for organic
structure determination.
 NMR Spectrometry is based on the measurement of
absorption of electromagnetic radiation in the radio
frequency region of roughly 4 to 900MHz. In
contrast to UV, IR and visible absorption, nuclei of
atoms rather than outer electrons are involved in
the process
 It is used to study a wide variety of nuclei:
 1H
 13C
 15N
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4. BASICS OF ATOMIC STRUCTURE
 What is atom?
 Composition of atom?
 What is molecule?
 What is atomic No.?
 What is atomic mass No.?
 Different charges on atom?
 What is spinning nuclei?
 What is spin quantum No.?
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5. 5

6. A
 Elements are composed of extremely
small particles called atoms. All atoms of
a given element are identical. The atoms
of one element are different from the
atoms of all other elements.
 A molecule is an aggregate of two or more
atoms in a definite arrangement held
together by chemical bonds.
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7. A
 Atomic No.- Number of Protons present in
the nuclei of atom.
 Atomic mass No.- Number of protons and
neutrons present in the nuclei of atom.
Atomic mass no.= No.of protons+ No. of
neutrons
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8. SPIN QUANTUM NUMBER
 Spin quantum no denoted by ‘I’
 Atom having I > o shows NMR spectra
 Spin quantum depends on atomic no.&
atomic mass no.
 No. of possible orientation calculated
using
(2 I +1)
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Mass NO. Atomic NO. Spin quantum No.
odd odd or even ½, 3/2, 5/2………
even even 0
even odd 1,2,3………………

9. WHAT IS NMR?
Nuclear Magnetic
Resonance
Matching of
frequencies
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In the Nucleus Involves Magnets

10. PRECESSIONAL FREQUENCY AND MOTION
 Proton is act as tiny magnet in external
magnetic field
 A slower waltz like motion of nuclei
around axis known as precessional
motion
 The precessional frequency may be
defined as the number of revolutions per
seconds made by the magnetic moment
vector of the nucleus around the external
field H0
 Eg. Spinning top 10

11. PRECESSIONAL FREQUENCE AND MOTION
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12. THEORY OF NMR
 Every charged nuclei having
property of spinning.
 Induced magnetic field.
 Resonance.
 Absorption of energy.
 Flipping phenomenon.
 Measurement of release energy.
 Relaxation process.
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13. THEORY OF NMR(FLIPPING PHENOMENON)
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14. ENERGY TRANSITION
 Nuclei with 2 allowed spin states can align
either with or against the field,
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15. T1 RELAXATION
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 T1 relaxation is sometimes called spin-lattice
relaxation.
 In this type of relaxation the energy lost as the
nucleus returns to the lower energy state is
transferred to the molecule in the form of
heat.This means that the total number of nuclei
in the excited state decreases.

16. T2 RELAXATION
 T2 relaxation is commonly refered as spin-spin
relaxation.
 In this type of relaxation the energy released
when a nucleus makes the transition from high to
low energy state is absorbed by another nucleus.
This allows the other nucleus to move from low
energy to high 16

17. T2 RELAXATION
 Short relaxation times result in broad
signals. Longer relaxation times then
produce narrower signals.
 An excited nucleus transfer it’s energy to
an unexcited nucleus of a similar
molecule that is nearby.
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18. LARMOR EQUATION
 v = (g/ 2π ) Bo
 g = Magnetogyric ratio
 Bo = Magnetic field
 Larmor frequency: The nuclei precess
about an axis parallel to the applied
magnetic field, with a frequency called the
Larmor Frequency (w)
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19. RELATION BETWEEN ‘V’ AND ‘Bo
Slow precession in small
magnetic field
Faster precession in larger
magnetic field
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20. INSTRUMENTATION
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21. ROLE OF DIFFERENT COMPONENT
 Strong magnet
 Radio frequency source(input
oscillator)
 A detector(output receiver)
 An amplifier
 Recorder
 Sample holder
 Coil around sample
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22. WORKING OF NMR SPECTROPHOTOMETER
 Sample under investigation taken in glass
tube
 Rf source is made to fall on sample by
feeding energy into the coil wound around
the sample holder
 A signal is detected if nuclei in sample
resonate with source
 Energy is transfer from via nuclei to
detector source
 Output from detector is fed to recorder
after amplification
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23. TYPES OF NMR
CW NMR spectroscopy
 Magnetic field is steady and tunable
radio frequency is use.
 It is operated on frequency sweep
method
FT-NMR spectroscopy
 Conversion of time domain spectra into
frequency domain spectra.
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24. NEW TRENDS IN NMR
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 FT-
NMR

25. ADVANTAGES OF FT-NMR OVER CWNMR
 More sensitive.
 It can measure weaker signal also,
 Required less time for scanning .
 Measurement of FID can performed in few
second.
 Suitable for examination of nuclei that are
not strongly magnetic.
 Also suitable for very dilute sample.
 Coupling constant is easily determine.
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26. SUMMARY
 In NMR spectroscopy the electromagnetic
radiation absorb in frequency region of 4-
900 MHz
 Nuclei of atom involved in process
 Atom having I>0 shows NMR spectra
 Unless and until nuclei of atom not
resonate with radio frequency it can not
give spectra
 More will be the strength of external
magnetic field more will be the frequency
of rotation 26

27. REFERENCES
 Skoog D.A, Holler F.J.& Crouch
S.R.,”Instrumental Analysis” Page No. 552-
567,577
 William Kemp, “Organic Spectroscopy” 3rd
edition,Published by Palgrave, Page No.
103-118.
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