2-Notes on Proton NMR Spectroscopy-1.pdf

-Notes on Proton NMR Spectroscopy-1.pdf

1. Nuclear Magnetic Resonance(NMR)
Spectroscopy
01-10-2024 1
Dr. Jorphin Joseph
Assistant Professor
Department of Chemical oceanography
CUSAT

2. Introduction
•Nuclearmagneticresonance(NMR)spectroscopyisalsoanabsorption
spectroscopyinwhichsamplesabsorbelectromagneticradiationintheradio-
frequencyregion(3MHzto30,000MHz)
•NMR signals were first observed in 1945
Independently by Prucell at Harvard and
Bloch at Stanford.
•Ethanol was the first compound studied(1945)
•In 1952, Prucell and Bloch won the Nobel Prize
in Physics for their discovery. Felix Bloch
Stanford
Edward Purcell
Harvard

3. Introduction
There are approximately 100 isotopes for which NMR spectroscopy is possible, but the most
commonly used by organic chemists are proton nuclear magnetic resonance (PMR or
1
H NMR)
spectroscopy and carbon-13 nuclear magnetic resonance (
13
C NMR) spectroscopy.
When ethanol was placed between pole pieces of an electromagnet and irradiated with
electromagnetic radiation it absorbed radiation in the radio frequency region. When
the magnetic field was turned off, NO absorption was observed.

4. Basic Theory-Spinning Nucleus
4
Orientationsofnuclearmagnetic
moments(µ)ormagneticdipolesofa
spinningnucleus
•Aspinningnucleusisassociatedwith
-anangularmomentum(P)
-magneticmoment(µ)
•Both(P)and(μ)arevectorquantitiesand
alsoquantized

5. Spinning Nucleus
01-10-2024 COD 5
Nucleiofsomeisotopespossessamechanicalspin,i.e.theyhaveangularmomentum.
Thetotalangularmomentumofaspinningnucleusdependsonitsspin,orspin
numberI(alsocalledasnuclearspinquantumnumber).Eachprotonandneutronhas
itsownspinandIisaresultantofthesespins,i.e.vectorcombinationofprotonand
neutronspins.
Unfortunately,thelawsgoverningthiscombinationarenotyetknown,hencethespin
ofaparticularnucleuscannotbepredictedingeneral.However,theobservedspinscan
berationalized.

6. Spinning Nucleus
6
Orientationsofnuclearmagnetic
moments(µ)ormagneticdipolesofa
spinningnucleus
•Theratioofmagneticmomentumtoangular
momentumiscalled“Gyromagneticratio”.
Itisverycharacteristicofagivennuclei.Itisa
constantforagivennucleus.
Gyromagneticratio=[γ]=(μ)/(P)

7. Spinning Nucleus in a Magnetic Field
7
0 0
αspin
βspin
H
0or B
0

8. Gyromagnetic Ratio(μ)/(P)

9. Energy transitions in NMR
H
0or B
0
Δ

10. Factors affecting energy gap between spin states
TheenergyrequiredforatransitionΔEisdirectlyproportionaltothestrengthoftheappliedmagnetic
field.ThisisshowngraphicallyinFig.Thestrongerthefield,greaterwillbethetendencyofthenuclear
magneticdipolestoremainalignedwithitandhigherwillbetheenergyrequiredforatransition.
300
H
0or B
0
H
H
0
0


11. Factors affecting energy gap between spin states

12. Factors affecting energy gap between spin states
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13. The sensitivity or intensity of magnetization
depends on….

14. Why modern NMR instruments use higher
operating frequencies?
01-10-2024 COD 14

15. The mechanism of absorption-Resonance
Whenthemagneticfieldisapplied,thenucleusbeginstoprecessaboutitsownaxisofspinwithangularfrequency,
whichissometimescalleditsLarmorfrequency.Thefrequencyatwhichaprotonprecessesisdirectlyproportionalto
thestrengthoftheappliedmagneticfield;thestrongertheappliedfield,thehighertherate(angularfrequencyω)of
precession.Foraproton,iftheappliedfieldis1.41Tesla(14,100Gauss),thefrequencyofprecessionisapproximately
60MHz.
Sincethenucleushasacharge,theprecessiongeneratesanoscillatingelectricfieldofthesamefrequency.If
radiofrequencywavesofthisfrequencyaresuppliedtotheprecessingproton,theenergycanbeabsorbed.Thatis,
whenthefrequencyoftheoscillatingelectricfieldcomponentoftheincomingradiationjustmatchesthefrequencyof
theelectricfieldgeneratedbytheprecessingnucleus,thetwofieldscancouple,andenergycanbetransferredfrom
theincomingradiationtothenucleus,thuscausingaspinchange.Thisconditioniscalledresonance,andthenucleus
issaidtohaveresonancewiththeincomingelectromagneticwave.

16. The mechanism of absorption-Resonance

17. The mechanism of absorption-Resonance

18. The mechanism of absorption-Resonance
B
0or H
0= Applied external magnetic field
M
0 = Net magnetization
ω = Precessionalfrequency
υ = Radio frequency or frequency of incoming radiation

19. 01-10-2024 COD 19
Instrumentation

20. 01-10-2024 COD 20
Instrumentation
High-field 700 MHz NMR spectrometer
300
High-field 500 MHz NMR spectrometer

21. NMR spectrum of ethyl chloride in CDCl
3at 60 MHz
01-10-2024 COD 21
Peak Position
Chemical environment of proton or
13
C
Peak Area
Number of protons in similar chemical environment
Peak Splitting
Neighborhood

22. Shielding, Deshielding and Chemical Shift
01-10-2024 SCAS 22

23. Shielding and Deshielding
01-10-2024 23
Fromtheaboveequationsoneinfersthatallthehydrogennucleiinamolecule,say
ethanolshouldhavethesameresonancefrequency,irrespectiveofitschemicalnature,
atagivenmagneticfield.
Butthisisnottrue.Hydrogensindifferentchemicalenvironmentgivedifferent
resonancefrequenciesintheNMR.
or

24. Shielding and Deshielding
01-10-2024 24
Undertheinfluenceoftheappliedmagneticfield,electronssurroundinganucleusstart
tocirculateperpendiculartotheappliedmagneticfieldH
0,andsotheygeneratea
secondarymagneticfieldcalledinducedmagneticfield(σH
0)whichopposestheapplied
magneticfieldintheregionofthenucleus,e.g.proton.Thus,thenucleusexperiencesa
weakermagneticfieldH
efflessthantheappliedmagneticfieldH
0,anditissaidtobe
shielded.Thistypeofshieldingistermeddiamagneticshielding(diamagnetic
anisotropy)anditseffectistermedasshieldingeffect.

25. Shielding, Deshielding, Chemical shift
01-10-2024 COD 25
lftheinducedfieldreinforcestheappliedfield,thenthefieldexperiencedbytheprotonis
greaterthantheappliedfield.Suchaprotonissaidtobedeshieldedandthiseffectis
termedasdeshieldingeffect.
Comparedtoanakedproton,ashieldedprotonrequiresahigherappliedfieldstrength,
whereasadeshieldedprotonrequiresalowerfieldstrengthfortransition.Thus,shielding
shiftstheabsorptionpositionupfield,whereasdeshieldingshiftstheabsorptionposition
downfieldandtheseeffectsaretermedasshieldinganddeshieldingeffects,respectively.
SuchshiftsintheNMRabsorptionpositionsarecalledchemicalshiftsbecausetheyarise
fromthecirculationofelectronsinchemicalbonds.Thechemicalshiftisexpressedasthe
differencebetweentheabsorptionpositionofaparticularprotonandtheabsorption
positionofareferenceproton.Duetovaryingelectronicenvironmentoftheprotonor
groupofprotons,theirabsorptionsignalsappearatdifferentfieldvalues.Thus,signalsin
PMRspectragiveinformationaboutthedifferentkindsofprotonsandtheirenvironments
inmolecules.

26. Why are the NMR absorption positions expressed
relative to a reference compound?
01-10-2024 COD 26

27. Why TMS is a good reference compound in NMR
spectroscopy?
01-10-2024 COD 27

28. Measurement of Chemical shift: NMR scale
01-10-2024 COD 28

29. Measurement of Chemical shift: NMR scale
01-10-2024 COD 29

30. Measurement of Chemical shift: NMR scale
01-10-2024 COD 30

31. Chemical shifts and scan widths
01-10-2024 COD 31

32. Problems
01-10-2024 COD 32

33. General regions of chemical shift for
1
H and
13
C
01-10-2024 COD 33
Shield
Upfield
Deshield
Downfield

34. General regions of chemical shift
1
H
01-10-2024 COD 34
Carboxylic acidsAldehyde Aromatic/ hetero aromatic
Olefinic hydrogen
Halogen /Oxygen
Acetylenic
Aliphatic alicyclic
Alcohols, Amines

35. 1.Electronegativity
01-10-2024 COD 35
Thedegreeofshieldingdependsontheelectrondensityaroundtheproton.Thehigherthe
electrondensityaroundaproton,thehighertheshieldingandhigheristhefield(lowerthe
δvalue)atwhichtheprotonabsorbs.Thus,theelectrondensityaroundaprotonsuccessfully
correlateswithitschemicalshift.Anearbyelectronegativeatomwithdrawselectrondensity
(dueto-Ieffect)fromtheneighbourhoodoftheproton,sotheNMRsignalofsuch
deshieldedproton(theprotonsurroundedbylesselectrondensity)willappeardownfield
(higherδvalue).
CH
3F CH
3ClCH
3BrCH
3I
4.26 3.052.682.16
H
3C H
3C-NH
3C-0
δin ppm0.9 2.2 3.5
CH
4 CH
3ClCH
2Cl
2CHCl
3
0.23 3.05 5.28 7 .24
CH
3ClCH
3CH
2Cl
3.05 1.48
TMS = 0.0
CH
4= 0.23

36. 2.Anisotropic effects
36
Inacetylenic,olefinic,aldehydicandaromaticprotons,chemicalshiftscannotbeexplained
onlyonthebasisofelectronegativity.Anisotropic(directiondependent)effectsproducedby
circulationofπelectronsundertheinfluenceoftheappliedmagneticfieldproducessome
changesinchemicalshifts.Theseeffectsdependontheorientationofthemoleculewith
respecttotheappliedfield.
Anisotropiceffectsareinadditiontotheinducedmagneticfieldgeneratedbythecirculation
ofσelectrons.Generally,theinducedmagneticfieldgeneratedbycirculatingπelectronsis
strongerthanthatgeneratedbyσelectrons.
Spherical electron density
Induced magnetic field will be uniform
in space isotropic effect
Example: s –electron –spherical
Non-spherical electron density
Induced magnetic field will be non-uniform in
space –anisotropic
Example: pi electron cloud of aromatic ring,
C=C and C=O type

37. 2.Anisotropic effects
37
Acetylenicprotonsaremuchmoreshieldedthan
expectedfromtheelectronegativityofthe
acetyleniccarbonsandtheyabsorbathigherfield.
Theinducedmagneticfieldreinforcestheappliedfield
resultingindeshieldingoftheolefinicprotons.
Consequently,theyabsorbatIowerfieldthanexpected
fromtheelectronegativityofolefiniccarbons..
δ1.80 δ5.28
shielding
deshielding
shielding
deshielding

38. 2.Anisotropic effects
38
Aldehydicprotonsabsorbatmuchlowerfield(δ-9.5)
duetothecombinedeffectsofthehigh
electronegativityofoxygenandanisotropiceffects
producedbytheπelectronsofthecarbonylgroup..

39. 2.Anisotropic effects
39
Thespacearoundadoublebondoranaromaticringcanbedividedintoshieldingand
deshieldingregionsandthatprotonspresentintheseregionswillabsorbatarelativelyhigh
andlowfield,respectively.
Theboundarybetweenshieldinganddeshieldingregionsresemblesthesurfaceofadouble
cone.

40. 2.Anisotropic effects
40
Bridged [10]-annulene
(42+2)= 10 electrons
Dimethyldihydropyrene
(43+2)= 14 electrons

41. 2.Anisotropic effects
41
Thisisapplicabletoheterocyclicsystemsandto
Annulenes,forexample,[18]annulenesustainsa
ringcurrent,sothatthetwelveperipheralprotons
aredeshieldedandthesixinternalprotons
shielded.Theouterprotonsappearatδ9.3,while
theinnerprotonsareatalowerfrequencythan
TMSatδ-3.0ppm.
Protonsheldaboveorbelowtheplaneofthering
resonateatlowδvaluesthanprotonsintheplaneofthe
ring.Indimethylderivativeofpyrene,themethylgroup
appearsatδ-4.2,lowerinfrequencythanTMS.This
showsthatthecyclicπ–electronsystemaroundthe
peripheryofthemoleculesustainsaringcurrentand
indicatesaromaticcharacterinanonbenzenoidring
system.Themethylgroupsareintheshieldingzoneand
appearasatsuchanextraordinaryδvalues.

42. σbond anisotropic effects in saturated compounds
42
Theequatorialprotonsincyclohexaneringscometoresonanceabove0.5δhigher
thantheaxialprotonsandthisisattributedtoanisotropicdeshieldingbyσelectrons
inβ-γbonds.

43. 2.Anisotropic effects
43
Diastereomers
Trans Cis
CisTrans

44. 3.Hydrogen bonding effects
44
Atlowconcentration,intermolecularH-bondingisdiminishedinsimple–OH,-NH,-SHcompounds.
HydrogenexperiencesanetdeshieldingeffectifhydrogenbondisstrongandisshieldedwhenH-bond
isweak,sinceHbondinvolveselectroncloudtransferfromHatomstoneighboringelectronegative
atomslikeO,N,Setc.Thusathighconcentration–OH,-NH,-SHprotonsaredeshielded,henceappear
athighδthanindilutesolutions.IncreasedtemperaturealsoreducesH-bonding,sotheδvaluesare
temperaturedependant.
IntramolecularH-bondingisunchangedbydilutionandtheNMRspectrumofsuchsystemsare
independentofconcentration.Intramolecularhydrogenbondingleadstohighdeshieldingofprotons.
Insalicylicacid,theOHresonanceatveryhighδ(10–12Hz)andenolOHappearsatevenhigher
values(11–16Hz).
Carboxylic acids are a special case of H-bonding, because of their stable dimerswhich persists even in
very dilute solutions, carboxylic OH appears between 10 and 13δ.

45. 4. van der Waals deshielding
45

46. Solvent effect on chemical shift
01-10-2024 COD 46

47. Chemical shifts of protons in
different chemical
environments
01-10-2024 COD 47
Example 1

48. Summary
01-10-2024 COD 48
PeakPosition
Chemicalenvironmentofprotonor
13
C
PeakArea
Numberofprotonsinsimilarchemicalenvironment
PeakSplitting
Neighborhood
Upfield-Shielding
Lower chemical shift
Downfield-Deshielding
Higher chemical shift

49. How can chemical equivalence of protons be judged?
01-10-2024 COD 49

50. How can chemical equivalence of protons be judged?
01-10-2024 COD 50
Z
H

51. How can chemical equivalence of protons be judged?
01-10-2024 COD 51

52. How can chemical equivalence of protons be judged?
01-10-2024 COD 52

53. How can chemical equivalence of protons be judged?
01-10-2024 COD 53

54. How can chemical equivalence of protons be judged?
01-10-2024 COD 54
Example 2:How many NMR signals do you expect from each of these
compounds?

55. How can chemical equivalence of protons be judged?
01-10-2024 COD 55
How many NMR signals do you expect from each of these compounds?
b

56. How can chemical equivalence of protons be judged?
01-10-2024 COD 56
c
c
d

57. How can chemical equivalence of protons be judged?
01-10-2024 COD 57
c

58. How can chemical equivalence of protons be judged?
01-10-2024 COD 58
c

59. Peak area and proton counting
01-10-2024 COD 59

60. 01-10-2024 COD 60
Peak area and proton counting

61. 01-10-2024 COD 61
Peak area and proton counting
Degree of Unsaturation/ Double bond equivalence/ Index of Hydrogen Deficiency
Gives you the sum of multiple bonds +
number of rings

62. 01-10-2024 COD 62
Peak area and proton counting
Degree of Unsaturation/ Double bond equivalence/ Index of Hydrogen Deficiency

63. 01-10-2024 COD 63
Peak area and proton counting

64. Summary
01-10-2024 COD 64
PeakPosition
Chemicalenvironmentofprotonor
13
C
PeakArea
Numberofprotonsinsimilarchemicalenvironment
PeakSplitting
Neighborhood

65. Effect of neighboring protons-Spin-Spin coupling or splitting
01-10-2024 COD 65

66. Effect of neighboring protons-Spin-Spin coupling or splitting
01-10-2024 COD 66

67. Spin-Spin coupling or splitting
01-10-2024 COD 67
ThesplittingofNMRsignalsiscausedby
spin-spincouplingwhichisindirect
couplingofprotonspinsthroughthe
interveningbondingelectrons.Thefield
experiencedbytheprotonisslightly
increasediftheneighbouringproton(the
protononadjacentcarbonorother
atoms,i.e.thevicinalproton)isaligned
withtheappliedfield;ordecreasedifthe
vicinalprotonisalignedagainstthe
appliedfield.Theabsorbingprotonthus
mayexperienceeachofthemodified
fieldsanditsabsorptionisshiftedupand
downfields,andthusthesignalissplit
intoagroupofpeaks(amultiplet).
2 possibilities
3 possibilities
4 possibilities
(n+1) Rule

68. Spin-Spin coupling or splitting
01-10-2024 COD 68
(n+1) Rule

69. Multiplicity-number of component peaks in multiplet
01-10-2024 COD 69
Itshouldbenotedthatspin-spinsplittingisobservedonlybetweennon-equivalent
(withdifferentchemicalshifts)neighbouringprotons.
Equivalentprotonsdospin-spincouplewithoneanotherbutsplittingisnotobserved.
Ingeneral,thenumberofcomponentpeaksinamultiplet(i.e.themultiplicity=n+1,
wherenisthenumberofequivalentprotonscausingthesplitting

70. Multiplicity-number of component peaks in multiplet
01-10-2024 COD 70
Examinethecaseathand,1,1,2-trichloroethane,utilizingthen+1Rule.Firstthelonemethinehydrogenissituated
nexttoacarbonbearingtwomethyleneprotons.Accordingtotherule,ithastwoequivalentneighbors(n=2)and
issplitinton+1=3peaks(atriplet).Themethyleneprotonsaresituatednexttoacarbonbearingonlyonemethine
hydrogen.Accordingtotherule,theseprotonshaveoneneighbor(n=1)andaresplitinton+1=2peaks(a
doublet).

71. Multiplicity-number of component peaks in multiplet
01-10-2024 COD 71

72. Multiplicity-number of component peaks in multiplet
01-10-2024 COD 72

73. Spin-spin coupling constant depends on…
01-10-2024 COD 73

74. Spin-Spin splitting patterns for I=½ nucleus like
1
H
01-10-2024 COD 74

75. Multiplicity-number of component peaks in multiplet
01-10-2024 COD 75

76. Line intensities of component peaks in a multiplet
01-10-2024 COD 76
Pascal’s triangle

77. General features of PMR spectra
01-10-2024 COD 77

78. Predict the number of signals and multiplicity in the
PMR spectra
01-10-2024 COD 78

79. Predict the number of signals and multiplicity in the
PMR spectra
01-10-2024 COD 79
Question: Indicate the types of protons and their multiplicity in the 1H NMR spectra of the
following compounds:

80. Predict the number of signals and multiplicity in the
PMR spectra
01-10-2024 COD 80

81. Predict the number of signals and multiplicity in the
PMR spectra
01-10-2024 COD 81

82. 01-10-2024 COD 82

83. 01-10-2024 COD 83

84. 01-10-2024 COD 84

85. Summary
Peak position
Peak area
Peak splitting
01-10-2024 COD 85
•Chemicalenvironmentof
1
Hor
13
C
•Electronegativity,hydrogenbond,
anisotropiceffects,vanderWaal’s
forces

86. Summary
Peak position
Peak area(height)
Peak splitting
01-10-2024 COD
•Numberofprotonswithsameδ

87. Summary
Peak position
Peak area(height)
Peak splitting
01-10-2024 COD 87
•Numberofprotonsintheneighbourhood
•Splittingpatterninthemultiplet:(n+1)or(n+1)(n’+1)….
•Intensitiesofpeaksinmultiplet:Pascalstriangle

88. Coupling Constant
01-10-2024 COD
88
Thedistancebetweenthecentres
oftwoadjacentpeaksinamultiplet
iscalledcouplingconstantorspin-
spincouplingconstant(J).The
valuesofcouplingconstantsJare
alwaysquotedinHzandnever
inδ(ppm)orτvalues.ThevalueofJ
remainsconstantindifferent
appliedmagneticfieldsorradio
frequenciesused,whereasthe
valuesofchemicalshifts(inHz)are
directlyproportionaltotheapplied
magneticfieldsorradio
frequencies.

89. Coupling Constant
01-10-2024 SCAS 89
Thisdifferencebetweenspin-spinsplittingand
chemicalshiftaffordsamethodfordistinguishing
betweenthem.Ifthespectrumofacompoundis
recordedatdifferentappliedmagneticfields,then
theseparationofsignals(inHz)duetochemical
shiftchange,whereasseparationoftwoadjacent
peaks(inHz)inamultipletremainsalways
constant.Thus,iftheseparationbetweenadjacent
peaksdoesnotchange,thentheyarecomponent
peaksofamultiplet.Ontheotherband,ifthe
separationbetweenthepeakschangeson
changingtheappliedfield,thentheyrepresent
differentsignalswithdifferentchemicalshifts.The
valuesofcouplingconstantsJbetweenprotons
generallyliebetween0and20Hz.

90. An illustration of the relationship between the
chemical shift and the coupling constant
01-10-2024 90

91. ‘Multiplet skewing’
01-10-2024 COD 91

92. A COMPARISON OF NMR SPECTRA AT LOW–AND
HIGH–FIELD STRENGTHS
01-10-2024 COD 92
TheNMRspectrumof1-
nitropropane.
(a)Spectrumdetermined
at60MHz;(b)spectrum
determinedat300MHz.

93. ‘Coupling could be confusing’
01-10-2024 COD 93
1:3:3:1
Quartet

94. 1. First order spectra
01-10-2024 COD 94

95. 1. First order spectra
01-10-2024 COD 95

96. 2. Second order spectra
01-10-2024 COD 96

97. Coupling Constants
Homonuclear Coupling
oCouplingbetweenhydrogenatomsonadjacentcarbon
atoms(vicinalcoupling)
o(n+1)rulegovernsthenumberofmultiplets
Heteronuclear Coupling
oCoupling between
13
C and attached hydrogens
01-10-2024 COD 97

98. Different types of coupling in NMR
01-10-2024 98
a)One-bond coupling-
1
J
b)Two-bond coupling(Geminal coupling)-
2
J
c)Three-bond coupling(Vicinal coupling)-
3
J
d)Large range coupling-
4
J-
n
J
- -

99. Different types of couplings
01-10-2024 99
a) One-bond coupling-
1
J
Protonsattachedtothe
13
Catomscausescouplingin
13
CNMR-Heteronuclearcoupling
- -

100. Different types of couplings
01-10-2024 100
b) Two-bond coupling(Geminal coupling)
2
J
oProtonsattachedtothesame
carbonatomarecalled
geminalprotons.
oTheseareseparatedbytwo
bonds,andwhentheyare
nonequivalent,theyshow
spin-spinsplitting.
oWhenscharacterincreases,
germinalcouplingconstant
valueincreases -

101. Different types of couplings
01-10-2024 101
Angle between bonds affect
2
Jgeminalcoupling
b) Two-bond coupling(Geminal coupling)
2
J

102. Different types of couplings
01-10-2024
102
Protons attached to adjacent atoms are called vicinal protons. These are separated by three bonds.
c) Three-bond coupling(Vicinal coupling)
3
J
Factors influencing the magnitude of
3J
HH.

103. Different types of couplings
103
⁓2 hz
c) Three-bond coupling(Vicinal coupling)
3
J
⁓10 hz
Dihedral angle affect
3
Jvicinalcoupling
φ
The Karplusrelationship—the approximate variation of
the coupling constant
3
J with the dihedral angle φ.

104. Different types of couplings
01-10-2024 104
c) Three-bond coupling(Vicinal coupling)
3
J
Dihedral angle affect
3
Jvicinalcoupling

105. Different types of couplings
01-10-2024 105
Valence angles in cyclic alkanes affect
3
J coupling of protons
The J
vicdecreases with increasing electronegativity of X in a freely rotating system
Electronegativity of attached group
3
J coupling of protons

106. Different types of couplings
01-10-2024 106
d) Long range coupling
4
J-
n
J

107. Different types of couplings
01-10-2024 107

108. A simplified correlation chart for proton chemical shift values.
01-10-2024 COD 108

109. A simplified correlation chart for proton chemical shift values.
01-10-2024 COD 109

110. Chemically Equivalent Protons
01-10-2024 COD 110
protons having same chemical environment; hence the same chemical shift (d)
Homo and enantiotopic hydrogens in organic molecules
isochronous

111. Magnetically Nonequivalent Protons
01-10-2024 COD 111

112. Magnetically Nonequivalent Protons
01-10-2024 COD 112

113. Magnetically Nonequivalent Protons
01-10-2024 COD 113

114. Magnetic equivalence
01-10-2024 COD 114
Magnetically as well as chemically equivalent

115. Assignment
01-10-2024 COD 115
Pavia-Exercise
Chapter: 3
Questions: 28
https://www.docbrown.info/page06/spectra/0spectra-nmr1h.htm

116. 01-10-2024 COD 116
Questions…!!