Chapter6Familiarreactionmechanisms1.ARadicalChainMechanism2.ElectrophilicadditiontoC,Cmultiple

bonds3.NucleophilicadditiontoC,Cmultiple

bonds4.ConcertedadditiontoC,Cmultiplebonds5.Substitutionreactions6.Eliminationreactions7.NamereactionsChapter6Familiarreactionm1Step1:Chaininitiation:

formationofradicalsfromnonradicalspeciesStep2:Step3:Chainpropagation:

reactionofradicalsandamoleculestoformanewradical1.1Alkanehalogenationreaction1.ARadicalChainMechanismStep1:Chaininitiation:forma2Chaintermination(Destructionofradicals):

DisproportionationCouplingChaintermination(Destruction3Bonddissociationenergy(kJ/mol)Bonddissociationenergy(kJ/m4Enthalpychange△H?Entropychange△S?Freeenergychange△G?Enthalpychange△H?5Howaboutthechlorinationofmethane?Howaboutthebrominationofpropene?Activity:F>Cl>Br>I;Allyl,3°>2°>1°Selectivity:F<Cl<Br<I;Allyl,3°>2°>1°Howaboutthechlorinationof61.2RadialOxidationwithOxygenChaininitiationChainpropagation1.2RadialOxidationwithOxyg7DrawamechanismforthefollowingreactionDrawamechanismforthefollo81.3.RadicaladditionreactionInitiationPropagationH-O428H-Cl432H-Br368C-Br272,H-Cl432,H-C403,pi鍵682－3681.3.Radicaladditionreaction92.ElectrophilicadditiontoC,Cmultiple

bonds2.1.CarbocationmechanismDirection:ThemorestablecarbocationformpreferentiallyCaution:Carbocationrearrangement!2.ElectrophilicadditiontoC10第六章常見反應機理課件112.2.NiumreactionmechanismminorcontributingstructureSterospecificity:Antiaddition2.2.Niumreactionmechanismmi12TheelectronegativitytellyouwhichoneisE+.Theelectronegativitytellyou132.3.Oxymercuration-Reduction2.3.Oxymercuration-Reduction14Abridgedmercurinium:three-center/two-electronbondAbridgedmercurinium:three-c153.NucleophilicadditiontoC,Cmultiple

bonds3.NucleophilicadditiontoC,164.ConcertedadditiontoC,CmultiplebondsAsynadditionmechanism4.1.Catalytichydrogenation4.ConcertedadditiontoC,Cm174.2.Hydroboration-Oxidation4.2.Hydroboration-Oxidation18第六章常見反應機理課件194.3.OsO4-OxidationCatalyticamountOsO4(expensiveandhighlytoxic)withperoxide4.3.OsO4-OxidationCatalytica204.4.KMnO4-Oxidation4.4.KMnO4-Oxidation214.5.Diels-Alderreaction4.5.Diels-Alderreaction22OverlapbetweenthehighestoccupiedMOofthediene(HOMO)andthelowestunoccupiedMOofthedienophile(LUMO)isthermallyallowedintheDielsAlderReaction,providedtheorbitalsareofsimilarenergy.Thereactionisfacilitatedbyelectron-withdrawinggroupsonthedienophile,sincethiswilllowertheenergyoftheLUMO.Overlapbetweenthehighestoc23Thereare“inversedemand”DielsAlderReactionsthatinvolvetheoverlapoftheHOMOofthedienophilewiththeLUMOofthediene.Thisalternativescenarioforthereactionisfavoredbyelectron-donatinggroupsonthedienophileandanelectron-poordiene.Thereare“inversedemand”24Theendoproductisusuallyfavoredbykineticcontrolduetosecondaryorbitalinteractions.Theendoproductisusuallyfa25Thereactionisdiastereoselective.Thereactionisdiastereoselec265.SubstitutionReactions5.1NuclephilicSubstitutionReactionsSN1SN25.SubstitutionReactions5.1N27SN1SN2TertiaryalkylPrimaryalkylPoornucleophileGoodnucleophilePolarsolventNonpolarsolventGoodLeavinggroupPoorleavinggroupSN1SN2Tertiaryalkyl285.2ElectrophilicAromaticSubstitutionReactions5.2ElectrophilicAromaticSub295.3NucleophilicAromaticSubstitutionReactionsR=groupwithboth-Iand-Ceffects5.3NucleophilicAromaticSubs306.EliminationreactionsE1E2E1cbSaytzeffruleHofmannrule6.EliminationreactionsE1E2E131HofmannruleHofmannrule32γ-branchesresultsinHofmannproductγ-branchesresultsinHofmann33第六章常見反應機理課件347.NameReactions7.1.Aldolcondensation7.NameReactions357.2.Arndt-EistertSynthesis-Wolffrearrangement

7.2.Arndt-EistertSynthesis-W367.3.BenzoinCondensation7.3.BenzoinCondensation37X.Linghu,J.S.Johnson,Angew.Chem.,2003,115,2638KeyIntermediate:X.Linghu,J.S.Johnson,Ange387.4.ClaisenCondensationKeyIntermediate:7.4.ClaisenCondensationKey39DieckmannCondensationDieckmannCondensation407.5.CannizzaroReaction7.5.CannizzaroReaction417.6.Diazotisation7.6.Diazotisation427.7.HaloformReaction

7.7.HaloformReaction437.8.Hell-Volhard-ZelinskyReaction7.8.Hell-Volhard-ZelinskyRea44第六章常見反應機理課件457.9.MannichReaction7.9.MannichReaction467.10.MichaelAdditiondonorsacceptors7.10.MichaelAdditiondonors477.11.ArbuzovReaction

Michaelis-ArbuzovReaction7.11.ArbuzovReaction

Michae487.12.ReformatskyReaction7.12.ReformatskyReaction497.13.Wolff-KishnerReduction7.13.Wolff-KishnerReduction50第六章常見反應機理課件51Chapter6Familiarreactionmechanisms1.ARadicalChainMechanism2.ElectrophilicadditiontoC,Cmultiple

bonds3.NucleophilicadditiontoC,Cmultiple

bonds4.ConcertedadditiontoC,Cmultiplebonds5.Substitutionreactions6.Eliminationreactions7.NamereactionsChapter6Familiarreactionm52Step1:Chaininitiation:

formationofradicalsfromnonradicalspeciesStep2:Step3:Chainpropagation:

reactionofradicalsandamoleculestoformanewradical1.1Alkanehalogenationreaction1.ARadicalChainMechanismStep1:Chaininitiation:forma53Chaintermination(Destructionofradicals):

DisproportionationCouplingChaintermination(Destruction54Bonddissociationenergy(kJ/mol)Bonddissociationenergy(kJ/m55Enthalpychange△H?Entropychange△S?Freeenergychange△G?Enthalpychange△H?56Howaboutthechlorinationofmethane?Howaboutthebrominationofpropene?Activity:F>Cl>Br>I;Allyl,3°>2°>1°Selectivity:F<Cl<Br<I;Allyl,3°>2°>1°Howaboutthechlorinationof571.2RadialOxidationwithOxygenChaininitiationChainpropagation1.2RadialOxidationwithOxyg58DrawamechanismforthefollowingreactionDrawamechanismforthefollo591.3.RadicaladditionreactionInitiationPropagationH-O428H-Cl432H-Br368C-Br272,H-Cl432,H-C403,pi鍵682－3681.3.Radicaladditionreaction602.ElectrophilicadditiontoC,Cmultiple

bonds2.1.CarbocationmechanismDirection:ThemorestablecarbocationformpreferentiallyCaution:Carbocationrearrangement!2.ElectrophilicadditiontoC61第六章常見反應機理課件622.2.NiumreactionmechanismminorcontributingstructureSterospecificity:Antiaddition2.2.Niumreactionmechanismmi63TheelectronegativitytellyouwhichoneisE+.Theelectronegativitytellyou642.3.Oxymercuration-Reduction2.3.Oxymercuration-Reduction65Abridgedmercurinium:three-center/two-electronbondAbridgedmercurinium:three-c663.NucleophilicadditiontoC,Cmultiple

bonds3.NucleophilicadditiontoC,674.ConcertedadditiontoC,CmultiplebondsAsynadditionmechanism4.1.Catalytichydrogenation4.ConcertedadditiontoC,Cm684.2.Hydroboration-Oxidation4.2.Hydroboration-Oxidation69第六章常見反應機理課件704.3.OsO4-OxidationCatalyticamountOsO4(expensiveandhighlytoxic)withperoxide4.3.OsO4-OxidationCatalytica714.4.KMnO4-Oxidation4.4.KMnO4-Oxidation724.5.Diels-Alderreaction4.5.Diels-Alderreaction73OverlapbetweenthehighestoccupiedMOofthediene(HOMO)andthelowestunoccupiedMOofthedienophile(LUMO)isthermallyallowedintheDielsAlderReaction,providedtheorbitalsareofsimilarenergy.Thereactionisfacilitatedbyelectron-withdrawinggroupsonthedienophile,sincethiswilllowertheenergyoftheLUMO.Overlapbetweenthehighestoc74Thereare“inversedemand”DielsAlderReactionsthatinvolvetheoverlapoftheHOMOofthedienophilewiththeLUMOofthediene.Thisalternativescenarioforthereactionisfavoredbyelectron-donatinggroupsonthedienophileandanelectron-poordiene.Thereare“inversedemand”75Theendoproductisusuallyfavoredbykineticcontrolduetosecondaryorbitalinteractions.Theendoproductisusuallyfa76Thereactionisdiastereoselective.Thereactionisdiastereoselec775.SubstitutionReactions5.1NuclephilicSubstitutionReactionsSN1SN25.SubstitutionReactions5.1N78SN1SN2TertiaryalkylPrimaryalkylPoornucleophileGoodnucleophilePolarsolventNonpolarsolventGoodLeavinggroupPoorleavinggroupSN1SN2Tertiaryalkyl795.2ElectrophilicAromaticSubstitutionReactions5.2ElectrophilicAromaticSub805.3NucleophilicAromaticSubstitutionReactionsR=groupwithboth-Iand-Ceffects5.3NucleophilicAromaticSubs816.EliminationreactionsE1E2E1cbSaytzeffruleHofmannrule6.EliminationreactionsE1E2E182HofmannruleHofmannrule83γ-branchesresultsinHofmannproductγ-branchesresultsinHofmann84第六章常見反