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ID:11462470
大小:2.95 MB
页数:63页
时间:2018-07-12
《浙江大学马成有机化学乙课件chapter7 conjugation in》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、2009/9/131Chapter7:ConjugationinAlkadienesandAllylicSystems2009/9/132SummaryAadjacentπsystemintheformofadouble(ortriple)bondcanalterthecharacteristicchemistryofthefunctionalgroup,duetotheeffectsofresonancewithinaconjugatedsystemThisπsystemdoesnothavetobeallCasin
2、aC=CorC≡Cbutcanalsocontainheteroatoms,e.g.C=OorC≡N1.Functionalgroups(independentunits,conjugationunits)2.AllylicSystem3.Dienes4.Conjugationaddition5.Diels-AlderReaction(M.O.)2009/9/1337.1Conjugation1.SomeDienesandPolyenes2009/9/1342.ConjugationInorganicchemistry
3、,Conjugationisusedtodescribe:π−πsystemsp-πsystemsσ-πsystemsCharacter:LoweredMoleculeEnergy1)Theactionnotdecreasewiththedistanceintheconjugationsystem2)Chargechangesonebyone(electronegativety,electroniccharge)Comaredtoinductiveeffect!Thefundamental---Orbitalinvol
4、vedinthebondingwithinthesystem1)Acontinuousarrayof"p"orbitalsthatcanaligntoproduceabondingoverlapalongthewholesystem.(parallelandco-plane)2)Inσ-πsystems,with"σ"orbitals,Pseudo-conjugationorSuper-conjugationTheEffectofthreeConjugation:π–π>p-π>σ-π2009/9/135⫠π–πCCC
5、CCCCNCCCOHCCCCCC2009/9/136Thenativeconformationofcyclooctatetraene.Adjacentdoublebondsarenotcoplanar,sothereisnotstrongconjugationbetweenthem2009/9/137•p–πClCCRCOOHCH3CHCHCH22009/9/138•σ-πandσ-pOOCH2CHCH3CCCHHHHHCH2CHCHHHCCHHH2CCHHHCH2HHCH3CCHHH2CCHHHHHCH2CH3200
6、9/9/139•ThestrengthofconjugationElectronegativityandMajorquantumnumberπ–π(-C)1)2)CCCCCCCNCCCO<CNR2009/9/1310•p–π(+C)•EN•Majorquantumnumber()NR2CCOHCCCCCCCCFCC>>2009/9/1311•Dienea)HeatofHydrogenation2009/9/1312•Anotherstereoisomericfactorassociatedwithconju
7、gateddienesexist:Rotationaboutthesinglebondjoiningthetwodoublebonds(coloredblue)convertsatrans-likes-transconformationtoitss-cisform.Theenergybarriertothisconformationalisomerisationisnormallylow,andthes-transconformerisoftenmorestablethanthes-cisconformer2009/9
8、/1313b)IoslatedandConjugateddienec)CumulatedDiene(allene)2009/9/13142009/9/1315•BondEnergyandBondLengthofSingleBond2009/9/1316•OtherConjugationsystems2009/9/13172.Res
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