3. 3
Introduction :
NMR : Nuclear Magnetic Resonance(NMR) is spectroscopy
technique which is based on the absorption of electromagnetic
radiation in the radio frequency region 4 to 900 Mhz by nuclei of
the atoms.
P NMR : Proton Nuclear Magnetic Resonance spectroscopy is
one of the most powerful tools for elucidating the number of
hydrogen or proton in the compound.
4. NMR Spectroscopy
1.Proton(1H) nuclear magnetic resonance (PMR or 1H-
NMR) .
2.Carbon (13C)nuclear magnetic resonance(13C-NMR).
3.Two Dimensional NMR (2D-NMR).
4
5. Principle of 1H NMR :
The principle behind NMR is that many
nuclei have spin and all nuclei are
electrically charged. If an external
magnetic field is applied ,an energy
transfer is possible between the base
energy to higher energy level.
5
6. • When proton is not in electric field proton are arranged in randomly.
• When electric field is applied proton arrange in antiparallel or parallel.
• Parallel =+1/2
Antiparallel=-1/2
6
8. Chemical shift
The position on the plot at which the nuclei absorbs is
called the chemical shift .
or
A Chemical Shift is defined as difference in parts per
million(ppm) between the resonance frequency of the
observed proton and tetramethylsilane (TMS) hydrogens.
The NMR spectrum is plot of intensity of NMR signals VS
magnetic field in reference to TMS. 8
9. Shielding of proton: High electron density around a nucleus
shields the nucleus from the external magnetic field and signal
are up field in the NMR spectrum.
Deshielding of proton: Lower electron density around a nucleus
Deshields the nucleus from the external magnetic field and the
signals are downfield in the NMR spectrum.
9
11. 1 H -NMR
•Nuclear Magnetic resonance spectroscopy
•Study of nucleus
11
O
OH
CH3
CH3
H3C
12. WHAT IS INSIDE THE NUCLEUS
12
1 Nucleus=Protons + Neutrons
2 These protons and neutrons spin around their own axis.
3. Each spin has magnitude of ½.
4. Magnitude of the spin of nucleus is because of Protons and
Neutrons(overall spin of the nucleus depend on spin of P and N)
5. If these spins are paired against each other , the nucleus of that atom
posses NO overall spin.
13. • If the number of neutrons and the number of protons
are both even , then the nucleus has No spin
• If the number of neutrons and the number of protons are
both odd then the nucleus has an integer spin (i.e.1,2,3)
• If the number of neutrons plus the number of protons is
odd ,then the nucleus has a half-integer
spin(1/2,3/2,5/2).so,1
1H and 6
13C can be studied
13
15. 1H-NMR=PROTON NMR=PMR
In the nucleus of hydrogen there is only one proton ,which is
responsible for the overall spin of hydrogen nucleus. So when
we study hydrogen nucleus means we are studying the spinning
proton hence we call it as proton NMR or PMR .
Spin Quantum Number: Spin quantum number describes the
angular momentum of an electron.
15
16. 1H-NMR spectrum :
16
4.Peak Multiplicity/Peak splitting : Due to spin –spin coupling . Based on N+1 rule .
Intensity of the peaks in multiplets is calculated using pascal triangle
3.Position of signal : Range of chemical shift value at which the peak will appear in
NMR spectrum
2.Intensity of signals: Height of the peak due to number of protons
(hydrogen ) represented by each peak.
1.Number of peak in 1H-NMR: Number of sets of equivalent protons
17. 1.Number of peak in 1H-NMR spectrum : Number of sets of
chemically equivalent protons
• Protons in different environments give different NMR signals.
• Protons in same chemical environment are called as equivalent
protons and such equivalent protons give the same NMR signal
17
H3C
O
CH3
H3C Cl
O
H3C
CH3
6 H Ha Hb Ha Hb Hc
1 peak 2 peak 3 peaks
18. Intensity of peak : Peak height
1.Number of signals=5
2.Peak intensity= Hc >Ha>Hb/Hd >He
o
OH
CH3
CH3
H3C
19. 3.Position of signals:
• Chemical shift:
He-Electronegative so it is in downfield region
19
O
OH
CH3
CH3
H3C
20. TMS
20
12 11 10 9 8 7 6 5 4 3 2 1 0
Chemical shift(ppm)
I
n
t
e
n
s
I
t
y
23. Multiplicity – The Spin-Spin Splitting
• Depending on how many neighbors it has, the signal of a given proton can
be split into lines. The simplest signal consists of one line and is called
a singlet, followed by the doublet, triplet, etc. A signal with more than seven
lines is referred to as a multiplet.
• The number of peaks is obtained by the N+1 rule, where N is the number of
neighboring protons.
• For example, if the proton has one neighbor, it gives a doublet (1+1), if there
are two adjacent protons, we get a triplet (2+1).
24
46. APPLICATION
47
• Bacterial identification and metabolic studies
1H NMR spectroscopy has been used for bacterial identification and quantification and for metabolic
pathways studies. Several studies have been conducted for the diagnosis of the bacteria that cause urinary
tract infections (UTI).
• Antimicrobial susceptibility assays
The use of 1H NMR spectroscopy for antimicrobial susceptibly tests has been not highly studied despite its
powerful utility in this area of study [5]. Application of 1H NMR spectroscopy to antimicrobial
susceptibility studies was first carried out on
• Applications in bio fluids
In the last few years, 1H NMR has been used to directly analyse biofluids and to diagnose different
diseases directly from body fluids. In this sense, it has been applied to analyse human microbiota from
faeces and urine samples
• Other types of analyses
The combination of NMR spectroscopy, with the use of isotopically substituted molecules as tracers is a
well‐established protocol in microbiology.
47. REFEENCE
1. Pavia DL, Lampman GM, Kriz GS. Introduction to Spectroscopy third
edition. Thomson Learning, Inc. 2001. p. 579.
2. Webb GA. NMR Spectroscopy. Annu Reports Prog Chem - Sect C.
1992;89(December):3–36.
3. https://m.chemicalbook.com/SpectrumEN_627-05-4_MS.htm
4. https://www.sciencedirect.com/topics/chemistry/1h-nmr-spectrum
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