Nmr nuclear magnetic resonance spectroscopyJoel Cornelio
Basics of NMR. Suitable for UG and PG courses.
Includes principle, instrumentation, solvents. chemical shift and factors affecting it. Some problems. resolving agents, coupling constant and much more
Nmr nuclear magnetic resonance spectroscopyJoel Cornelio
Basics of NMR. Suitable for UG and PG courses.
Includes principle, instrumentation, solvents. chemical shift and factors affecting it. Some problems. resolving agents, coupling constant and much more
Two dimensional Nuclear Magnetic Resonance (2D NMR) refers to a set of multi pulse techniques which were introduced to overcome the complex spectra obtained with NMR.
It is a set of NMR methods which give data plotted in a space defined by two frequency axes rather than one.
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy, is a spectroscopic technique to observe local magnetic fields around atomic nuclei.
Introduction & Definition, Theory, instrumentation, Continuous – wave (CW) instrument, The pulsed Fourier Transform [FT] instrument, Solvents, Chemical shift
i. Shielding and de-shielding
ii. Factors affecting chemical shift
CHEMICAL SHIFT AND ITS FACTOR EFFECTS, COUPLING CONSTANT, FIRST ORDER TO NON FIRST ORDER, SPIN SYSTEMS, CHEMICAL EQUIVALENCE AND NON EQUIVALENCE, TIRUMALA SANTHOSHKUMAR S
NMR SPECTROSCOPY ,Relaxation,longitudinal / spin- spin relaxation,transverse / spin- spin relaxation,Shielding of proton ,Deshielding of proton,CHEMICAL SHIFT,Factors Influencing Chemical Shift,Inductive effect, Vander Waal’s deshielding,Anisotropic effect (space effect),Hydrogen bonding
,SPLITTING OF THE SIGNALS,COUPLING CONSTANT,NMR SIGNAL IN VARIOUS COMPOUND
Two dimensional Nuclear Magnetic Resonance (2D NMR) refers to a set of multi pulse techniques which were introduced to overcome the complex spectra obtained with NMR.
It is a set of NMR methods which give data plotted in a space defined by two frequency axes rather than one.
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy, is a spectroscopic technique to observe local magnetic fields around atomic nuclei.
Introduction & Definition, Theory, instrumentation, Continuous – wave (CW) instrument, The pulsed Fourier Transform [FT] instrument, Solvents, Chemical shift
i. Shielding and de-shielding
ii. Factors affecting chemical shift
CHEMICAL SHIFT AND ITS FACTOR EFFECTS, COUPLING CONSTANT, FIRST ORDER TO NON FIRST ORDER, SPIN SYSTEMS, CHEMICAL EQUIVALENCE AND NON EQUIVALENCE, TIRUMALA SANTHOSHKUMAR S
NMR SPECTROSCOPY ,Relaxation,longitudinal / spin- spin relaxation,transverse / spin- spin relaxation,Shielding of proton ,Deshielding of proton,CHEMICAL SHIFT,Factors Influencing Chemical Shift,Inductive effect, Vander Waal’s deshielding,Anisotropic effect (space effect),Hydrogen bonding
,SPLITTING OF THE SIGNALS,COUPLING CONSTANT,NMR SIGNAL IN VARIOUS COMPOUND
It would be use full to All Needy People. It involve information about NMR Spectroscopy ( a spectroscopic techniques), factors influencing , proton NMR and their applications of NMR as well as Nuclear magnetic imaging.
A Strategic Approach: GenAI in EducationPeter Windle
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In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
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The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
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Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
Honest Reviews of Tim Han LMA Course Program.pptxtimhan337
Personal development courses are widely available today, with each one promising life-changing outcomes. Tim Han’s Life Mastery Achievers (LMA) Course has drawn a lot of interest. In addition to offering my frank assessment of Success Insider’s LMA Course, this piece examines the course’s effects via a variety of Tim Han LMA course reviews and Success Insider comments.
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This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
Instructions for Submissions thorugh G- Classroom.pptx
NMR SPECTROSCOPY AND SOME PROBLEMS BASED ON IT
1. Nuclear Magnetic
Resonance (NMR) Spectroscopy
By
Dr. Kalam Sirisha,
Associate Professor & Head,
Department of Pharmaceutical Chemistry,
Vaagdevi College of Pharmacy, Ramnagar, Warangal, Telangana
E-mail: ragisirisha@yahoo.com
2. 2
Introduction
• Nuclear magnetic resonance (NMR) is a physical phenomenon in
which nuclei in a magnetic field absorb and re-emit
electromagnetic radiation.
• NMR spectroscopy is the most powerful tool available for organic
structure determination.
• It is used to study a wide variety of nuclei (1
H,13
C,15
N, 19
F, 31
P etc).
• Most common types of NMR: proton and carbon-13
• 1
H NMR (PMR): To determine the type and number of H atoms
and spatial arrangement of them in a molecule.
• 13
C NMR (CMR): To determine the type and number of carbon
atoms and spatial arrangement of them in a molecule.
• The source of energy in NMR is radio waves which have long
wavelengths (75-0.5m), and thus low energy and frequency (4-
600MHz).
3. 3
Nuclear Spin
• A nucleus with an odd atomic number (no. of protons or
electrons) or an odd mass number (no. of neutrons and
protons in the nucleus) has a nuclear spin.
• If the number of neutrons plus the number of protons is odd,
then the nucleus has a half-integer spin (i.e. 1/2, 3/2, 5/2)
• 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)
• A nucleus of spin I will have 2I + 1 possible orientations.
• A nucleus with spin 1/2 (1
H & 13
C) will have 2 possible
orientations.
6. The magnetic fields of the spinning nuclei will align
either with the external field, or against the field.
6
7. 7
Two Energy States
A photon with the right amount of energy can be
absorbed and cause the spinning proton to flip.
8. 8
∆E and Magnet Strength
• Energy difference is proportional to the magnetic field
strength.
∆E = hν = γ h B0
2π
• Gyromagnetic ratio, γ, is a
constant for each nucleus.
γ=µ/p µ-dipole moment
p-angular momentum
• In a 14,092 gauss field, a 60 MHz
photon is required to flip a proton.
• A nucleus is in resonance when it
absorbs RF radiation and “spin flips” to a higher energy
state.
9. Larmor Precession
Spinning particle precesses about the external magnetic
field axis at an angular frequency known as Larmor
frequency.
9
fo = γ Bo
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11. 11
1
H NMR
Magnetic Shielding:
• If all protons absorb the same amount
of energy in a given magnetic field, not
much information can be obtained.
• But protons are surrounded by
electrons that shield them from the
external field.
• Circulating electrons create an induced
magnetic field that opposes the external
magnetic field. =>
13. 13
Protons in a Molecule
Depending on their chemical environment,
protons in a molecule are shielded by
different amounts.
=>
14. 14
NMR Signals
• The number of signals shows how many
different kinds of protons are present.
• The location of the signals shows how
shielded or deshielded the proton is.
• The intensity of the signal shows the
number of protons of that type.
• Signal splitting shows the number of
protons on adjacent atoms. =>
15. 15
Number of Signals
• Protons within a compound experience different magnetic
environments, which give a separate signal in the NMR spectrum
• Equivalent: Protons that reside in the same magnetic environment are
termed chemically equivalent. They have the same chemical shift.
Equivalent Non-equivalent
=>
16. Position of signals (chemical shift)
• The position on the horizontal frequency scale at which
the equivalent proton signals occur is called a chemical
shift.
• The chemical shift depends on the varying local
magnetic fields from the neighboring protons.
16
17. 17
Chemical Shift
• Measured in parts per million (ppm), called the delta
(δ) scale.
• Ratio of shift downfield from TMS (Hz) to total
spectrometer frequency (MHz).
• Same value for 60, 100, or 300 MHz machine.
• Tau ( ) value=10-Ƭ δ
=>
19. 19
Tetramethylsilane (TMS)
• TMS is added to the sample.
• Since silicon is less electronegative
than carbon, TMS protons are highly
shielded. Signal defined as zero.
• Organic protons absorb downfield (to
the left) of the TMS signal.
=>
Si
CH3
CH3
CH3
H3C
20. 20
Location of Signals
• More electronegative
atoms deshield more and
give larger shift values.
• Effect decreases with
distance.
• Additional electronegative
atoms cause increase in
chemical shift.
=>
24. 24
Spin-Spin Splitting
• Nonequivalent protons on adjacent carbons have
magnetic fields that may align with or oppose the
external field.
• This magnetic coupling causes the proton to
absorb slightly downfield when the external field is
reinforced and slightly upfield when the external
field is opposed.
• All possibilities exist, so signal is split and splitting
patterns (Multiplicity) results.
=>
32. 32
Range of Magnetic
Coupling
• Equivalent protons do not split each other.
• Protons bonded to the same carbon will
split each other only if they are not
equivalent.
• Protons on adjacent carbons normally will
couple.
• Protons separated by four or more bonds
will not couple.
=>
35. 35
Coupling Constants
• Distance between the peaks of multiplet
• Measured in Hz
• Not dependent on strength of the external
field
• Multiplets with the same coupling
constants may come from adjacent groups
of protons that split each other.
=>
37. 37
O-H and N-H Signals
• Chemical shift depends on concentration and solvent.
• Hydrogen bonding in concentrated solutions deshield the
protons, so signal is around δ3.5 for N-H and δ4.5 for O-H.
• Proton exchanges between the molecules may broaden the
peak.
=>
=>
38. 38
Identifying the O-H
or N-H Peak
• To verify that a particular peak is due to O-H or N-H, shake
the sample with D2O (heavy water).
• Deuterium will exchange with the O-H or N-H protons.
• On a second NMR spectrum the peak will be absent, or
much less intense.
=>
39. 39
Time Dependence
• Molecules are tumbling relative to the
magnetic field, so NMR is an averaged
spectrum of all the orientations.
• Axial and equatorial protons on
cyclohexane interconvert so rapidly that
they give a single signal.
• Proton transfers for OH and NH may occur
so quickly that the proton is not split by
adjacent protons in the molecule.
=>
41. 41
Carbon-13
• 13
C has a magnetic spin, but is only 1% of the carbon in a sample.
• It is more difficult to obtain a 13
C-NMR spectrum than a 1
H-NMR
spectrum. The difficulty stems from two sources:
• 1.the natural abundance of 13
C is low, so there are fewer NMR-
active nuclei per mole of compound to absorb energy.
• 2.the inherent signal intensity per nucleus is less for 13
C than
for 1
H. For equal numbers of 1
H and 13
C nuclei, the signal intensity
for 13
C is roughly 1/4 that of 1
H. When combined with the fact that
the natural abundance of 13
C is roughly 1% of that of 1
H, this means
that the signal intensity of 1
H is over 400 times greater than that of
13
C.
Hundreds of spectra are taken, averaged.
=>
42. 42
13
C-NMR: Number of Signals
Number of 13
C-NMR signals reveals equivalent carbons
•One signal per unique carbon type
•Reveals molecular symmetry
Examples
CH3CH2CH2CH2OH CH3CH2OCH2CH3
Two 13
C-NMR signals
2 x CH3 equivalent
2 x CH2 equivalent
No equivalent carbons
Four 13
C-NMR signals
Symmetry exists when # of 13
C-NMR signals < # of carbons in formula
43. 43
13
C-NMR: Position of Signals
•Position of signal relative to reference = chemical shift
•13
C-NMR reference = TMS = 0.00 ppm
•13
C-NMR chemical shift range = 0 - 250 ppm
•Downfield shifts caused by electronegative atoms and pi electron clouds
OH does not have carbon
↓
no 13
C-NMR OH signal
Example: HOCH2CH2CH2CH3
45. 45
13
C-NMR: Integration
1
H-NMR: Integration reveals relative number of hydrogens per signal
13
C-NMR: Integration reveals relative number of carbons per signal
•Rarely useful due to slow relaxation time for 13
C
time for nucleus to relax from
excited spin state to ground state
48. 48
Differences in
13
C Technique
• Resonance frequency is ~ one-fourth,
15.1 MHz instead of 60 MHz.
• Peak areas are not proportional to
number of carbons.
• Carbon atoms with more hydrogens
absorb more strongly.
=>
49. 49
Spin-Spin Splitting
• It is unlikely that a 13
C would be adjacent
to another 13
C, so splitting by carbon is
negligible.
• 13
C will magnetically couple with
attached protons and adjacent protons.
• These complex splitting patterns are
difficult to interpret.
=>
50. 50
13
C-NMR: Spin-Spin Coupling
•Spin-spin coupling of nuclei causes splitting of NMR signal
•Only nuclei with I ≠ 0 can couple
•Examples: 1
H with 1
H, 1
H with 13
C, 13
C with 13
C
•1
H NMR: splitting reveals number of H neighbors
•13
C-NMR: limited to nuclei separated by just one sigma bond; no pi bond “free spacers”
Conclusions
•Carbon signal split by attached hydrogens (one bond coupling)
1
H
13
C
13
C
12
C
Coupling observed
Coupling occurs but signal very weak:
low probability for two adjacent 13
C
1.1% x 1.1% = 0.012%
No coupling: too far apart
No coupling: 12
C has I = 0
51. 51
Proton Spin Decoupling
• To simplify the spectrum, protons are
continuously irradiated with “noise,” so
they are rapidly flipping.
• The carbon nuclei see an average of all
the possible proton spin states.
• Thus, each different kind of carbon
gives a single, unsplit peak.
=>
52. 52
Off-Resonance Decoupling
• 13
C nuclei are split only by the protons
attached directly to them.
• The N + 1 rule applies: a carbon with N
number of protons gives a signal with
N + 1 peaks.
=>
53. 53
Interpreting 13
C NMR
• The number of different signals indicates
the number of different kinds of carbon.
• The location (chemical shift) indicates the
type of functional group.
• The peak area indicates the numbers of
carbons (if integrated).
• The splitting pattern of off-resonance
decoupled spectrum indicates the
number of protons attached to the
carbon. =>
56. If molecular formula is given, calculate the double
bond equivalence to know the level of unsaturation
in the molecule
56
57. 57
1) Predict the number of peaks that you would expect in the PMR spectrum of
the following compounds by assigning equivalent and non-equivalent protons.
CHOOCH3
i) ii)
CH3 COO CH2 CH3
iii)
CH3 C CH2 CH3
CH3
OH
iv)
CH3 C CH2 Cl
CH3
CH3 v)
NH2 COO CH2 CH3
2) Propose the structure corresponding to the following spectrum
Mol. Formula : C3
H7
Cl
δ ppm splitting Integration
3.7 t 2.0
1.75 m 2.0
1.0 t 3.0
58. 58
3) What splitting pattern you would expect in the PMR of the protons in the
following compounds:
CH
CH3
CH3
a) b) c)
d) e)
CH3
O
CH2
N
CH3
CH3
Br
H
H
NO2
H
H
CH2
CH2
CH2
O
CH3
C
CH3
CH3 O CH2 CH3
4) Give a structure or structures consistent with the following CMR data:
Mol. Formula : C3
H8
O
CMR data: a) δ 14.7 (q)
b) δ 57.6 (q)
c) δ 67.9 (t)