大二有機七章

ChapterSevenHalogen-SubstitutedHydrocarbonsNomenclatureofHalogen-SubstitutedHydrocarbonsStructureofHalogen-SubstitutedHydrocarbonsPreparationofHalogen-SubstitutedHydrocarbons.ChemicalPropertiesofHalogen-SubstitutedHydrocarbonsClassificationofHalogen-SubstitutedHydrocarbonsClassificationofHalogen-SubstitutedHydrocarbonsHalogen-substitutedhydrocarbon：Thecompoundthatone(ormore)hydrogenatominahydrocarbonissubstitutedby

halogenatom.鹵代烴Classification:a.Accordingtothehydrocarbon:Alkylhalogen:CH3CH2CH2XAlkenylhalogen:Alkynylhalogen:Arylhalogen:ClassificationofHalogen-SubstitutedHydrocarbons2.AccordingtothedegreeofcarbonPrimaryhalideTertiaryhalideSecondaryhalideReviewPrimaryhalide1oRX

Tertiaryhalide3oRX

Secondaryhalide2oRX

ArylhalidesVinylhalidesBenzylhalidesAllylhalidesChapterSevenHalogen-SubstitutedHydrocarbonsNomenclatureofHalogen-SubstitutedHydrocarbonsStructureofHalogen-SubstitutedHydrocarbonsPreparationofHalogen-SubstitutedHydrocarbons.ChemicalPropertiesofHalogen-SubstitutedHydrocarbonsClassificationofHalogen-SubstitutedHydrocarbonsNomenclatureofHalogen-SubstitutedHydrocarbonsAlkylhalidesarenamedinthesamewayasalkanes,bytreatingthehalogenasasubstituentonaparentchain.Therearethreerules:Rule1:

Findthelongestcarbonchainandnameitastheparent.Ifadoubleortriplebondispresent,theparentchainmustcontainit.Rule2:Numberthecarbonatomsoftheparentchain,beginningattheendnearerthefirstsubstituent,regardlessofwhetheritisalkylorhalo.Assigneachsubstituentanumbertoitspositiononthechain.Rule3:

Iftheparentchaincanbeproperlynumberedfromeitherendbyrule2,beginattheendnearerthesubstituent(eitheralkylorhalo)thathasalphabeticalprecedence.Forexample:NomenclatureofHalogen-SubstitutedHydrocarbons5-Bromo-2,4-dimethylheptane2-Chloro-5-methylhexane1-Chlorocyclohexene1,2-Dibromobenzene(R)-3-Chloro-2,3-dimethylpentaneChapterSevenHalogen-SubstitutedHydrocarbonsNomenclatureofHalogen-SubstitutedHydrocarbonsStructureofHalogen-SubstitutedHydrocarbonsPreparationofHalogen-SubstitutedHydrocarbonsChemicalPropertiesofHalogen-SubstitutedHydrocarbonsClassificationofHalogen-SubstitutedHydrocarbonsPreparationofHalogen-SubstitutedHydrocarbons(a)FreeRadicalSubstitutionofAlkanesandCycloslksnes:(b)AdditionsofSmallCycloalkanes:FromAlkanesandCycloalkanes:(a)AdditionofHalogenstoAlkenes:PreparationofHalogen-SubstitutedHydrocarbons(b)HydrohalogenationofAlkenes:(c)FreeRadicalSubstitutionofAlkenes:FromAlkenes:(a)HydrohalogenationofAlkynes:PreparationofHalogen-SubstitutedHydrocarbons(a)AromaticHalogenation:(b)HalogenationofAlkylbenzeneSideChains:FromAlkynes:FromAromaticHydrocarbons:PreparationofAlkylHalidesfromAlcohols:Themostgeneralmethodforpreparingalkylhalidesistomakethemfromalcohols(醇).ThesimplestmethodforconvertinganalcoholtoanalkylhalideinvolvestreatingthealcoholwithHCl,HBr,orHI.PreparationofHalogen-SubstitutedHydrocarbonsthionylchloride

亞硫酰氯

Primaryandsecondaryalcoholsarebestconvertedintoalklyhalidesbytreatmentwithsuchreagentsasthionylchloride(SOCl2)orphosphorustrihalides(PX3).ChapterSevenHalogen-SubstitutedHydrocarbonsNomenclatureofHalogen-SubstitutedHydrocarbonsStructureofHalogen-SubstitutedHydrocarbonsPreparationofHalogen-SubstitutedHydrocarbonsChemicalPropertiesofHalogen-SubstitutedHydrocarbonsClassificationofHalogen-SubstitutedHydrocarbons

Sincehalogensaremoreelectro-negativethancarbon.TheC-Xbondisthereforepolar,withthecarbonatombearingaslightpositivecharge(δ+)andthehalogenaslightnegativecharge(δ-).StructureofHalogen-SubstitutedHydrocarbons1.Thestructureofalkylhalides(鹵代烷)2.ThestructureofvinylhalidesandarylhalidesStructureofHalogen-SubstitutedHydrocarbonsvinylichalidesarylhalidesVinylicandarylicC-Xbondsaremorestablethanthecorrespondingsaturatedbondsandarethereforemoredifficulttobebrokenp-πconjugatedeffectChapterSevenHalogen-SubstitutedHydrocarbonsNomenclatureofHalogen-SubstitutedHydrocarbonsStructureofHalogen-SubstitutedHydrocarbonsPreparationofHalogen-SubstitutedHydrocarbonsChemicalPropertiesofHalogen-SubstitutedHydrocarbonsClassificationofHalogen-SubstitutedHydrocarbons1.NucleophilicSubstitutionsofAlkylHalidesChemicalPropertiesofHalogen-SubstitutedHydrocarbons

Alkylhalidescanundergosubstitutionofthe

Xgroupbythenucleophile(Nu:)Reactivity:Substrate底物Leavinggroup離去基團ChemicalPropertiesofHalogen-SubstitutedHydrocarbons堿性水解制備醇，一般伯，仲鹵代烴Williamson合成不對稱醚，伯鹵代烴生成腈(nitrile)，碳鏈增長的反應(yīng)生成硫醚(sulfide)合成碳鏈增長的炔烴硝酸酯(nitrate)NegativelychargedNu:-

P219ChemicalPropertiesofHalogen-SubstitutedHydrocarbonsThisreactioncanbeusedtodifferentiate(區(qū)別)halogen-substitutedhydrocarbons.RPhenomenonGiveprecipitateimmediatelyGiveprecipitateafterheatingGiveprecipitateafterheatingforalongtimeNoreactionChemicalPropertiesofHalogen-SubstitutedHydrocarbonsRelativelyreactivity:

1oRX>2oRX>3oRX

Thisreactioncanbeusedtodifferentiate(區(qū)別)

chloro-substitutedhydrocarbonandbromo-substitutedhydrocarbon.Thedrivingforceofthisreactionisthedifferentsolubilityinacetone:NaIcandissolveinacetone,NaBrandNaClareinsolubleinacetone.ChemicalPropertiesofHalogen-SubstitutedHydrocarbonsNeutralNu:2.The

SN2ReactionandSN1ReactionChemicalPropertiesofHalogen-SubstitutedHydrocarbons(1)TheSN2Reaction----雙分子反應(yīng)(bimolecular)ν=k[CH3Br][OH-]let’slookatthekineticsofasimplenucleophilicsubstitutionofCH3BrwithOH-toyieldCH3OHplusBr-.therateofdisappearanceofreactant(反應(yīng)物)isequaltoaconstantofktimesthealkylhalideconcentration(濃度)timesthehydroxideion(OH-)concentration.Sotherateofthisreactionisdependentontheconcentrationsoftwospecies,andthereactionis

second-order(二級)

reaction.ThemechanismofSN2:ChemicalPropertiesofHalogen-SubstitutedHydrocarbonsThereactiontakesplaceinasinglestepwithoutintermediates.2-Bromobutane2-Butanol(1).ThisreactionoccursthroughatransitionstateinwhichthenewHO-CbondispartiallyformingatthesametimethattheoldC-Brispartiallybreaking.transitionstate(S)-(R)-(2).Thestereochemistry

atcarbonisinverted.(WaldenInversion)沃爾頓翻轉(zhuǎn)ChemicalPropertiesofHalogen-SubstitutedHydrocarbons

ThecharacteristicsoftheSN2reaction:(a)Thesubstrate(RX):stericeffectintheSN2reactionSN2transitionstate:stericallyhinderedalkylhalideatomis“shielded”nucleophileisdifficulttoapproachtheenergyofT.S.ishighthereactionisslowCH3X>1oRX>2oRX>3oRXReactivityofalkylsubstrates:ChemicalPropertiesofHalogen-SubstitutedHydrocarbonsHighestreactivityP,πconjugatedeffect,reinforcetheC-Xbonds

noreactionTherelativereactivityofsubstratesin

SN2:

PhCH2XCH2=CHCH2XCH3

>1oRX>2oRX>3oRX>ChemicalPropertiesofHalogen-SubstitutedHydrocarbons(b)Thenucleophile(親核試劑):Highnucleophilicity(親核性)isfavorabletotheSN2reaction.Nucleophilicityroughlyparallelsbasicity:Nucleophilicity:measuretheaffinityforacarbonatomBasicity:measuretheaffinityforaprotonNucleophilicityusuallyincreasegoingdownacolumnoftheperiodictable:ChemicalPropertiesofHalogen-SubstitutedHydrocarbonsNegativelycharged(負電荷的)nucleophilesareusuallymoreactivethanneutral(中性的)ones.(c)Theleavinggroup:Thebestleavinggroupshouldbeaweakbases(弱堿).Leavinggro