NMR Spectroscopy: Basic Principles, Concepts and Applications in Chemistry

2013·11.79 MB·English

by  Harald Günther

HaraldGu¨nther
NMRSpectroscopy
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Harald Gu¨nther
NMR Spectroscopy
Basic Principles, Concepts, and Applications in Chemistry
Third, completely revised and updated edition
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V
Contents
Preface XV
1 Introduction 1
1.1 Literature 8
1.2 UnitsandConstants 9
References 10
PartI BasicPrinciplesandApplications 11
2 ThePhysicalBasisoftheNuclearMagneticResonanceExperiment.
PartI 13
2.1 TheQuantumMechanicalModelfortheIsolatedProton 13
2.2 ClassicalDescriptionoftheNMRExperiment 16
2.3 ExperimentalVerificationofQuantizedAngularMomentum
andoftheResonanceEquation 17
2.4 TheNMRExperimentonCompactMatterandthePrinciple
oftheNMRSpectrometer 19
2.4.1 HowtoMeasureanNMRSpectrum 19
2.5 MagneticPropertiesofNucleibeyondtheProton 25
References 27
3 TheProtonMagneticResonanceSpectraofOrganic
Molecules – ChemicalShiftandSpin–SpinCoupling 29
3.1 TheChemicalShift 29
3.1.1 ChemicalShiftMeasurements 32
3.1.2 IntegrationoftheSpectrum 35
3.1.3 StructuralDependenceoftheResonanceFrequency – AGeneral
Survey 37
3.2 Spin–SpinCoupling 41
3.2.1 SimpleRulesfortheInterpretationofMultipletStructures 46
3.2.2 Spin–SpinCouplingwithOtherNuclei 49
3.2.2.1 NucleiofSpinI= 1 49
2
VI Contents
3.2.2.2 NucleiofSpinI> 1 51
2
3.2.3 LimitsoftheSimpleSplittingRules 52
3.2.3.1 TheNotionofMagneticEquivalence 52
3.2.3.2 SignificanceoftheRatioJ/ν δ 56
0
3.2.4 Spin–SpinDecoupling 58
3.2.5 Two-DimensionalNMR – theCOSYExperiment 60
3.2.6 StructuralDependenceofSpin–SpinCoupling – AGeneral
Survey 62
References 66
4 GeneralExperimentalAspectsofNuclearMagneticResonance
Spectroscopy 67
4.1 SamplePreparationandSampleTubes 67
4.2 InternalandExternalStandards;SolventEffects 70
4.3 TuningtheSpectrometer 74
4.4 IncreasingtheSensitivity 78
4.5 MeasurementofSpectraatDifferentTemperatures 81
References 83
Textbooks 83
ReviewArticles 83
5 ProtonChemicalShiftsandSpin–SpinCouplingConstants
asFunctionsofStructure 85
5.1 OriginofProtonChemicalShifts 86
5.1.1 InfluenceoftheElectronDensityattheProton 87
5.1.2 InfluenceoftheElectronDensityatNeighboringCarbonAtoms 87
5.1.3 TheInfluenceofInducedMagneticMomentsofNeighboringAtoms
andBonds 94
5.1.4 RingCurrentEffectinCyclicConjugatedπ-Systems 101
5.1.5 AlternativeMethodstoMeasureDiatropicity 110
5.1.6 DiamagneticAnisotropyoftheCyclopropaneRing 113
5.1.7 ElectricFieldEffectofPolarGroupsandthevan-derWaalsEffect 114
5.1.8 ChemicalShiftsthroughHydrogenBonding 117
5.1.9 ChemicalShiftsofProtonsinOrganometallicCompounds 119
5.1.10 SolventEffects 120
5.1.11 EmpiricalSubstituentConstants 121
5.1.11.1 TablesofProtonResonancesinOrganicMolecules 122
5.2 Proton–ProtonSpin–SpinCouplingandChemicalStructure 122
5.2.1 TheGeminalCouplingConstant(2J) 123
5.2.1.1 DependenceontheHybridizationoftheMethyleneCarbon 123
5.2.1.2 EffectofSubstituents 124
5.2.1.3 AMolecularOrbitalModelfortheInterpretationofSubstituent
Effectson2J 126
5.2.2 TheVicinalCouplingConstant(3J) 128
5.2.2.1 DependenceontheDihedralAngle 129
Contents VII
5.2.2.2 DependenceupontheC–CBondLength,Rμν 130
5.2.2.3 DependenceonHCCValenceAngles 132
5.2.2.4 SubstituentEffects 133
5.2.3 Long-RangeCouplingConstants(4J,5J) 137
5.2.3.1 SaturatedSystems 138
5.2.3.2 UnsaturatedSystems 139
5.2.4 Through-SpaceandDipolarCoupling 143
5.2.5 TablesofSpin–SpinCouplingConstantsinOrganicMolecules 144
References 147
Monograph 148
ReviewArticles 148
6 TheAnalysisofHigh-ResolutionNuclearMagneticResonance
Spectra 149
6.1 NotationforSpinSystems 150
6.2 QuantumMechanicalFormalism 151
6.2.1 TheSchro¨dingerEquation 151
6.3 TheHamiltonOperatorforHigh-ResolutionNuclearMagnetic
ResonanceSpectroscopy 153
6.4 CalculationofIndividualSpinSystems 155
6.4.1 StationaryStatesofaSingleNucleusA 156
6.4.2 TwoNucleiwithoutSpin–SpinInteraction(J =0);Selection
ij
Rules 156
6.4.3 TwoNucleiwithSpin–SpinInteraction(J (cid:2)=0) 158
ij
6.4.3.1 TheA CaseandtheVariationalMethod 158
2
6.4.3.2 CalculationoftheRelativeIntensities 162
6.4.3.3 SymmetricandAntisymmetricWaveFunctions 163
6.4.4 TheABSystem 164
6.4.5 TheAXSystemandtheFirst-OrderApproximation 167
6.4.6 GeneralRulesfortheTreatmentofMoreComplexSpinSystems 170
6.5 CalculationoftheParametersν andJ fromtheExperimental
i ij
Spectrum 174
6.5.1 DirectAnalysisoftheABSystem 175
6.5.2 SpinSystemswithThreeNuclei 177
6.5.2.1 TheAB (A B)System 177
2 2
6.5.2.2 TheParticleSpin 181
6.5.2.3 TheABXSystem 182
6.5.3 SpinSystemswithFourNuclei–TheAA(cid:3)XX(cid:3)System 192
6.5.4 ComputerAnalysis 206
References 209
Textbooks 210
ReviewArticles 210
VIII Contents
7 TheInfluenceofMolecularSymmetryandChiralityonProtonMagnetic
ResonanceSpectra 211
7.1 SpectralTypesandStructuralIsomerism 211
7.2 InfluenceofChiralityontheNMRSpectrum 216
7.3 AnalysisofDegenerateSpinSystemsbyMeansof13CSatellitesand
H/DSubstitution 226
References 229
ReviewArticles 230
PartII AdvancedMethodsandApplications 231
8 ThePhysicalBasisoftheNuclearMagneticResonanceExperiment.
PartII:PulseandFourier-TransformNMR 233
8.1 TheNMRSignalbyPulseExcitation 234
8.1.1 ResonancefortheIsolatedNucleus 234
8.1.2 PulseExcitationforaMacroscopicSample 236
8.2 RelaxationEffects 239
8.2.1 LongitudinalorSpin–LatticeRelaxation 239
8.2.2 TransverseorSpin–SpinRelaxation 243
8.2.3 ExperimentsforMeasuringRelaxationTimes 247
8.2.3.1 T Measurements – theInversionRecoveryExperiment 247
1
8.2.3.2 TheSpinEchoExperiment 248
8.3 PulseFourier-Transform(FT)NMRSpectroscopy 249
8.3.1 PulseExcitationofEntireNMRSpectra 250
8.3.2 TheReceiverSignalanditsAnalysis 252
8.4 ExperimentalAspectsofPulseFourier-TransformSpectroscopy 254
8.4.1 TheFTNMRSpectrometer – BasicPrinciplesandOperation 254
8.4.1.1 TheComputerandtheAnalog–DigitalConverter(ADC) 254
8.4.1.2 RFSourcesofanFTNMRSpectrometer 258
8.4.1.3 TransmitterandSignalPhase 259
8.4.1.4 SelectiveExcitationandShapedPulsesinFTNMRSpectroscopy 260
8.4.1.5 PulseCalibration 263
8.4.1.6 CompositePulses 264
8.4.1.7 SingleandQuadratureDetection 264
8.4.1.8 PhaseCycles 266
8.4.2 ComplicationsinFTNMRSpectroscopy 267
8.4.3 DataImprovement 269
8.5 DoubleResonanceExperiments 272
8.5.1 HomonuclearDoubleResonance – SpinDecoupling 272
8.5.2 HeteronuclearDoubleResonance 273
8.5.3 BroadbandDecoupling 275
8.5.3.1 BroadbandDecouplingbyCWModulation 275
8.5.3.2 BroadbandDecouplingbyPulseMethods 276
8.5.4 Off-ResonanceDecoupling 277
References 279