核磁共振波谱（兰州大学） Chapter 3_J Coupling

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1、Inlastcourse,weweretalkingabout…Inlastcourse,weweretalkingabout…•OriginofChemicalShift•DefinitionofChemicalShift•TheoryofChemicalShift•FactorsAffectingChemicalShift•1HChemicalShiftsofCommonStructuresTheOriginofChemicalShiftB0B0=fluxdensityoftheν<νstationarymagneticfieldeff1ν=appli

2、edfrequency1ν=effectivefrequencyeffatresonanceγ=magnetogyricratioσ=shieldingconstantDefinitionofChemicalShift(δ)()AratiooffrequencydifferencebetweentheresonanceandthatofTMSandoperatingfrequencyδ(ppm:partpermillion)TheoryofChemicalShiftB=-σBBMagneticFieldStrength10σShieldingConstan

3、tInMolecules:σ=σ+σdpInBiggerMolecules:σ=σ(loc)+σ(loc)+σ+σ+σ+σdparesσDiamagneticShieldingEffectdσParamagneticDeshieldingEffectpσAnisotropicShieldingEffectaσRingCurrentEffectrσElectronicFieldEffecteσSolventEffectsFactorsAffectingChemicalShifts•SubstitutionandHybridization•Inductivea

4、ndConjugativeEffects•AnisotropicEffects•vanderWaalsForce•Hydrogen-Bonding•SolventEffects1HChemicalShiftsofCommonStructuresChapter3:Spin-SpinCouplingandSpinSystems•MechanismofSpin-SpinCoupling•Homonuclear1HCoupling•n+1RuleinFirst-OrderSpectra•HeteronuclearCoupling•ChemicalShiftEqui

5、valenceandMagneticEquivalence•MultipletesforVariousTypesofSpinSystemsProtonSpin-SpinCoupling-CH3CH-CH2OHTheMechanismofSpin-SpinCouplingCHACHBABH=H(1-σ)±H’A0ABH=H(1-σ)±H’B0BATheMechanismofSpin-SpinCouplingDiracModelofJCouplingH-DHD1JH-DH-C-C-HH-O-DOCCHDHH3J2JH-C-C-HH-O-DHomonuclear

6、1HCoupling:TheSimplifiedPicture-CH2-CH3CH3CH2CH2m=-1/2B0m=+1/2M=m1+m2+m3+…+1/2-1/2-1/2+1/2ProtonSpin-Coupling:n+1RulePascal’sTriangleProtonSpin-Couplingandn+1RuleHcHbHb(n+1)(m+1)(n+1)(n+1)(m+1)J>JJ=JJ>JabbcabbcbccdProtonSpin-Couplingandn+1RuleHcHc(n+1)(m+1)(n+1)J

7、minalKarplusCorrelation2JforCHGroupsasaFunctionofH-C-HAnglesHH2H2JHH5HZHHCθH2J0–3HHHHZHHH2J12–18HZHHTheVincinalKarplusCorrelationRelationshipbetweenDihedralAngle(Φ)and3JCouplingConstantsHH2J,3JCouplingConstantsofAlkanesHHHH(4J)HH2J,3JCouplingConstantsofAlkanesHHHHa-eProtonCoupling

8、sinCyclicCompounds:Applicationofn