OrbitalInteractionTheoryofOrganicChemistry,SecondEdition.ArviRauk Copyright(2001JohnWiley&Sons,Inc. ISBNs:0-471-35833-9(Hardback);0-471-22041-8(Electronic) OrbitalInteractionTheoryofOrganicChemistry,SecondEdition.ArviRauk Copyright(2001JohnWiley&Sons,Inc. ISBNs:0-471-35833-9(Hardback);0-471-22041-8(Electronic) ORBITAL INTERACTION THEORY OF ORGANIC CHEMISTRY Second Edition ORBITAL INTERACTION THEORY OF ORGANIC CHEMISTRY Second Edition ARVI RAUK ProfessorEmeritus Universityof Calgary, Canada AJohn Wiley& Sons, Inc., Publication New York (cid:15) Chichester (cid:15) Weinheim (cid:15) Brisbane (cid:15) Singapore (cid:15) Toronto Designationsusedbycompaniestodistinguishtheirproductsareoftenclaimedastrademarks. InallinstanceswhereJohnWiley&Sons,Inc.,isawareofaclaim,theproductnamesappear ininitialcapitalorallcapitalletters.Readers,however,shouldcontacttheappropriate companiesformorecompleteinformationregardingtrademarksandregistration. Copyright(2001byJohnWiley&Sons,Inc.Allrightsreserved. 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CONTENTS PREFACE xiii 1 SYMMETRY AND STEREOCHEMISTRY 1 Purpose / 1 DefinitionofaGroup / 2 MolecularPointGroups / 2 SchoenfliesNotation / 2 InterrelationsofSymmetryElements / 3 TypeClassification / 3 IsomerismandMeasurements / 6 StereoisomerismofMolecules / 8 StereotopicRelationshipsofGroupsinMolecules / 9 AsymmetricSynthesisandStereochemistry / 10 NMRandStereochemistry / 12 SymmetryandStructuralParameters / 14 NoteonHybridization / 15 SymmetryandOrbitals / 16 AtomicOrbitals / 16 MolecularandGroupOrbitals / 17 InWhatCombination? / 19 2 MOLECULAR ORBITAL THEORY 20 Introduction / 20 ElectronicSchro¨dingerEquation(A.1) / 21 v vi CONTENTS FockEquations(A.42) / 23 TheBasisSet(STO-3G,6-31G*,andAllThat) / 24 OrbitalEnergiesandOrbitals / 25 RepresentationofMOs / 27 TotalEnergiesandtheHartree–FockLimit / 29 SuccessesandFailuresofHartree–FockTheory / 29 BeyondHartree–Fock / 30 DensityFunctionalTheory / 31 GeometryOptimization / 31 NormalCoordinatesandHarmonicFrequencyAnalysis / 32 ZeroPointVibrationalEnergies / 33 3 ORBITAL INTERACTION THEORY 34 RelationshiptoHartree–FockEquations / 34 Hu¨ckelApproximation / 34 OrbitalEnergiesandTotalElectronicEnergy / 34 CaseStudyofaTwo-OrbitalInteraction / 35 Case1:e (cid:136)e ,S (cid:136)0 / 38 A B AB Case2:e (cid:136)e ,S >0,S f1 / 39 A B AB AB Case3:e >e ,S (cid:136)0 / 40 A B AB Case4:e >e ,S >0 / 42 A B AB E¤ectofOverlap / 44 EnergeticE¤ectofOverlap / 44 OrbitalE¤ectofOverlap / 44 FirstLookatBonding / 45 RelationshiptoPerturbationTheory / 45 GeneralizationsforIntermolecularInteractions / 46 EnergyandChargeDistributionChangesfromOrbitalInteraction / 47 Four-Electron,Two-OrbitalInteraction / 47 Three-Electron,Two-OrbitalInteraction / 48 Two-Electron,Two-OrbitalInteraction / 49 One-Electron,Two-OrbitalInteraction / 51 Zero-Electron,Two-OrbitalInteraction / 51 InteractionsbetweenMolecules:ManyElectrons,ManyOrbitals / 52 GeneralPrinciplesGoverningtheMagnitudeofh andS / 52 AB AB InteractionsofMOs / 52 ElectrostaticE¤ects / 55 GroupOrbitals / 56 Zero-CoordinatedAtoms / 56 MonocoordinatedAtoms / 57 DicoordinatedAtoms / 58 TricoordinatedAtoms / 59 TetracoordinatedAtoms / 59 CONTENTS vii AssumptionsforApplicationofQualitativeMOTheory / 61 Example:CarbonylGroup / 62 ConstructionofInteractionDiagram / 62 InterpretationofInteractionDiagram / 65 ChemicalReactivity / 66 WhyDoesItWorkandWhenMightitNot? / 69 4 SIGMA BONDS AND ORBITAL INTERACTION THEORY 72 C—XsBonds:X(cid:136)C,N,O,FandX(cid:136)F,Cl,Br,I / 72 sBonds:HomolyticversusHeterolyticCleavage / 74 HeterolyticCleavageofsBondsInvolvingCorH / 74 HomolyticCleavageofsBondsInvolvingCorH / 75 HomonuclearsBondsC—C,N—N,O—O,F—F,Cl—Cl, Br—Br,andI—I / 76 InteractionsofsBonds / 77 sBondsasElectronDonorsorAcceptors / 81 sBondsasElectronAcceptors / 81 AsasAcceptor / 81 AsapAcceptor / 82 sBondsasElectronDonors / 83 AsasDonor / 83 AsapDonor / 84 BondinginCyclopropane / 84 5 SIMPLE HU¨CKEL MOLECULAR ORBITAL THEORY 86 SimpleHu¨ckelAssumptions / 86 ChargeandBondOrderinSHMOTheory:(S (cid:136)0,OneOrbitalper AB Atom) / 91 ElectronPopulationandNetChargeofCenterA / 91 BondOrderbetweenCentersAandB / 92 FactorsGoverningEnergiesofMOs:SHMOTheory / 92 ReferenceEnergyandEnergyScale / 92 HeteroatomsinSHMOTheory / 93 E¤ectofCoordinationNumberonaandb / 93 HybridizationatCinTermsofaandb / 96 GrossClassificationofMoleculesontheBasisofMOEnergies / 96 6 REACTIONS AND PROPERTIES OF pBONDS 98 ReactionsofOlefins(Alkenes) / 98 E¤ectofX:Substituents / 99 E¤ectofZSubstituents / 101 E¤ectof‘‘C’’Substituents / 101 E¤ectofDistortionofMolecularSkeleton / 102 viii CONTENTS Alkynes / 103 pBondstoandbetweenHigherRowElements / 103 pBondstoSilicon,Phosphorus,andSulfur / 103 7 REACTIVE INTERMEDIATES 105 . ReactiveIntermediates[CH ](cid:135),[CH ](cid:255),[CH ],and[:CH ] / 105 3 3 3 2 Carbocations / 105 IntermolecularReactionsofCarbocations / 106 IntramolecularReactionsofCarbocations / 107 SilylCations / 108 Carbanions / 108 CarbonFreeRadicals / 110 Carbenes / 114 NitrenesandNitreniumIons / 116 Nitrenes / 116 NitreniumIons / 118 8 CARBONYL COMPOUNDS 121 ReactionsofCarbonylCompounds / 121 ElectrophilicAttackonaCarbonylGroup / 121 BasicityandNucleophilicityoftheOxygenAtom / 122 NucleophilicAttackonaCarbonylGroup / 124 AmideGroup / 126 ThermodynamicStabilityofSubstitutedCarbonylGroups / 127 9 NUCLEOPHILIC SUBSTITUTION REACTIONS 129 NucleophilicSubstitutionatSaturatedCarbon / 129 UnimolecularNucleophilicSubstitutionS 1 / 129 N BimolecularNucleophilicSubstitutionS 2 / 130 N AnotherDescriptionoftheS 2Reaction:VBCMModel / 134 N 10 BONDS TO HYDROGEN 137 HydrogenBondsandProtonAbstractionReactions / 137 HydrogenBonds / 137 SymmetricalandBifurcatedHydrogenBonds / 139 ProtonAbstractionReactions / 141 E2EliminationReaction / 143 E1cBMechanismReaction / 144 E1EliminationReaction / 144 ReactionwithElectrophiles:HydrideAbstractionandHydride Bridging / 145 ActivationbypDonors(X:and‘‘C’’Substituents) / 145 CONTENTS ix HydrideAbstraction / 145 HydrideBridges / 147 ReactionwithFreeRadicals:HydrogenAtomAbstractionandOne-or Three-ElectronBonding / 147 Hydrogen-BridgedRadicals / 147 HydrogenAtomTransfer / 148 11 AROMATIC COMPOUNDS 150 ReactionsofAromaticCompounds / 150 CyclicpSystemsbySimpleHu¨ckelMOTheory / 150 Aromaticityins-BondedArrays? / 151 ReactionsofSubstitutedBenzenes / 152 ElectrophilicSubstitutions / 152 E¤ectofSubstituentsonSubstrateReactivity / 153 ElectrophilicAttackonX:-SubstitutedBenzenes / 153 ElectrophilicAttackonZ-SubstitutedBenzenes / 154 ElectrophilicAttackon‘‘C’’-SubstitutedBenzenes / 155 ElectrophilicAttackonNAromatics:PyrroleandPyridine / 155 NucleophilicSubstitutions / 157 E¤ectofSubstituentsonSubstrateReactivity / 158 NucleophilicAttackonZ-SubstitutedBenzenes / 158 NucleophilicAttackonNAromatics:PyrroleandPyridine / 158 NucleophilicSubstitutionbyProtonAbstraction / 159 12 PERICYCLIC REACTIONS 161 GeneralConsiderations / 161 CycloadditionsandCycloreversions / 162 StereochemicalConsiderations / 162 ElectrocyclicReactions / 165 StereochemicalConsiderations / 165 CheletropicReactions / 165 StereochemicalConsiderations / 165 SigmatropicRearrangements / 166 StereochemicalConsiderations / 166 ComponentAnalysis(AllowedorForbidden?) / 167 RuleforComponentAnalysis / 168 Diels–AlderReaction / 169 CopeRearrangement / 170 1,3-DipolarCycloadditionReactions / 171 13 ORGANOMETALLIC COMPOUNDS 175 TransitionMetals / 175 x CONTENTS LigandsinTransitionMetalComplexes / 176 OrbitalsinTransitionMetalBonding / 176 OrbitalEnergies / 178 ValenceOrbitalsofReactiveMetalComplexes / 179 SixValenceOrbitalsofTricoordinatedMetal / 182 FiveValenceOrbitalsofTetracoordinatedMetal / 182 FourValenceOrbitalsofPentacoordinatedStructure / 185 TransitionMetalsandC—HorH—HSigmaBonds / 186 MoreAboutCLigandsinTransitionMetalComplexes / 186 ChelatingLigands / 187 Organicp-BondedMoleculesasLigands / 187 TransitionMetalBondingtoAlkenes:Zeise’sSalt / 187 AgosticInteraction / 191 Ziegler–NattaPolymerization / 192 OxidativeAdditiontoH—HandC—HBonds / 194 14 ORBITAL AND STATE CORRELATION DIAGRAMS 196 GeneralPrinciples / 196 Woodward–Ho¤manOrbitalCorrelationDiagrams / 197 CycloadditionReactions / 197 ElectrocyclicReactions / 198 CheletropicReactions / 201 PhotochemistryfromOrbitalCorrelationDiagrams / 201 LimitationsofOrbitalCorrelationDiagrams / 203 StateCorrelationDiagrams / 203 ElectronicStatesfromMOs / 205 RulesforCorrelationofElectronicStates / 206 Example:CarbeneAdditiontoanOlefin / 206 15 PHOTOCHEMISTRY 209 Photoexcitation / 209 JablonskiDiagram / 210 FateofExcitedMoleculeinSolution / 211 Dauben–Salem–TurroAnalysis / 212 NorrishTypeIIReactionofCarbonylCompounds / 213 NorrishTypeICleavageReactionofCarbonylCompounds / 215 APPENDIX A: DERIVATION OF HARTREE–FOCK THEORY 218 ElectronicHamiltonianOperator / 218 ElectronicSchro¨dingerEquation / 220 ExpectationValues / 221 Many-ElectronWaveFunction / 221