有机化学Chapter3.Alkenes烯烃

Chapter3Alkenes3.1AlkeneNomenclature3.2StructureofAlkenes3.3IsomerisminAlkenes

3.3.1Stereo-isomerisminAlkenes3.3.2NamingStereoisomericAlkenes1.NamingbytermCis-trans2.NamingbytheE,ZNotationalSystem

3.4ReactionsofAlkenes

3.4.1ElectrophilicAdditionofAlkenes(烯烃亲电加成）

(1)AdditionofHydrogenHalidestoAlkenes（烯烃与卤化氢加成）

Orientationofelectrophilicaddition

（亲电加成的方向）

MechanismoftheReaction（反应机理）

Thestabilityofcarbocations（碳正离子的稳定性）

CarbocationRearrangements（碳正离子的重排）

Peroxideeffect（过氧化物效应）(2)AdditionofSulfuricacidtoAlkenes

（烯烃与硫酸加成）(3)Acid-catalyzedHydrationofAlkenes

(酸催化的烯烃水合反应)(4)Hydroboration-Oxidationofalkenes

（硼氢化-氧化反应）(5)AdditionofHalogentoAlkenes（与卤素加成）

(6)ConversionofAlkenestoVicinalHalohydrin(邻卤代醇)3.4.2HydrogenationofAlkenes(烯烃的氢化反应）

Heatofhydrogenation（氢化热）

Stabilitiesofalkenes（烯烃的稳定性）

Mechanismofalkeneshydrogenation

（烯烃加氢的反应机理）

StereochemistryofAlkeneshydrogenation(烯烃加氢的立体化学)

Heterogeneousreaction（异相反应）3.4.3OxidationofAlkenes（烯烃的氧化）

(1)Epoxidationofalkenes（烯烃的环氧化）

(2)Hydroxylationofalkenes（烯烃的羟基化）

(3)Oxidativecleavageofalkenes:

（烯烃氧化断键）

(A)Ozonolysisofalkenes（烯烃的臭氧化）

(B)WithKMnO4solution

（烯烃的高锰酸钾氧化）3.4.4ReactionofAlkeneswithAlkenes:Polymerization（聚合反应）Alkenes:

(Olefin)Hydrocarboncontainingcarbon-carbondoublebondThesiteofreactionsThefunctionalgroup（反应部位）（官能团）AliphatichydrocarbonsSaturated(饱和烃)Unsaturated(不饱和烃)AlkanescycloalkanesAlkenesAlkynesP74Isobutylene（异丁烯）α- Pinene（α-蒎烯）3.1NomenclatureofAlkenesIUPACNames:1.Givethebasenamebyselectingthelongestcontinuouscarbonchainincludingthedoublebond.-ene

（某烯）2.Number:Givethedouble-bondcarbonsthelowernumber.3.Thelocationofsubstituentslikealkanes.4.WhenCnumberisover10:称某碳烯5-Undecene5-十一碳烯2-Ethyl-1-pentene4,4-DimethylcyclohepteneAlkenylgroups（烯基）:Vinyl（乙烯基）Allyl(Allylicgroup)（烯丙基）Propenyl（丙烯基）Isopropenyl（异丙烯基）Methenecyclohexane（亚甲基环己烷）P773.2StructureofAlkenesStructureofEthylene:sp2HybridorbitalsP13,1.9C:Groundstate2p2s1sPromotionofelectronExcitatedstate2p2s1ssp2-hybridizedstate1s2psp2Hybri-dizationAnsp2orbital1/3sorbital2/3porbitalThreeequivalentsp2

hybridorbitalslieinaplaneatangleof120°tooneanother.GeometricstructureofCatomwithsp2-hybrid:

Planartriangle(平面三角)Asingleunhybridizedporbitalperpendiculartothesp2plane.

TheformationofC-Cπbond:2p-2psidebysideoverlap.TheformationofC-Hσbond:

sp2-1soverlap.OneC-Cσbondand4C-Hσbondarecoplanar.TheformationofC-Cπbond:2p-2psidebysideoverlap.InthemoleculeofEthylene:TheformationofC_Cσbond:sp2_sp2overlapporbitaloverlapHHHHσ-bondporbitaloverlapCCσbondπbondCarbon-carbondoublebondModelsofEthylene分子的不饱和度(Degreeofunsaturation)只含碳、氢、氧、氮以及单价卤素的计算公式：

Ω＝C＋1－(X－N)/2其中，C代表碳原子的数目，X代表氢和卤素原子的总数，N代表氮原子的数目，氧和其他二价原子对不饱和度计算没有贡献，故不需要考虑氧原子数。这种方法只适用于含碳、氢、单价卤素、氮和氧的化合物。补充理解说明：(1）若有机物为含氧化合物，因为氧为二价，C=O与C=C“等效”，所以在进行不饱和度计算时可不考虑氧原子。如CH2=CH2、CH3CHO、CH3COOH的不饱和度Ω为1。

2）有机物分子中的卤素原子取代基，可视作氢原子计算不饱和度Ω。如：C2H3Cl的Ω为1，其他基团如-NH2、-SO3H等都视为氢原子。(3）有机物分子中含有N、P等三价原子时，每增加1个三价原子，则等效为减少1个氢原子。如，CH3NH2的不饱和度Ω=0。(4）C=C，C=N碳碳双键的不饱和度Ω=1；碳碳叁键，C≡N的不饱和度Ω=2,环状化合物的不饱和度Ω=1。不饱和度计算的用途先写出分子式，然后根据分子式计算不饱和度，来推测分子中可能的双键，三键或者环的个数。3.3IsomerisminAlkenes3.3.1Stereo-isomerism

inAlkenes1-Butene2-MethylpropyleneIsobutenecis-2-Butenetrans-2-ButeneConstitutionalisomers(I)(III)(IV)(II)(I)(II)(III)(IV)Stereoisomers(III)(IV)Cis-transisomersThedifferentspacialarrangementofatomsoratomicgroups.cis-2-Butenetrans-2-ButeneRotationaboutC-CdoublebondisrestrictedConfigurationPhysicalproperties:m.p;b.p3.3.2NamingStereoisomericAlkenes1.NamingbytermCis-transThesameatomsoratomicgroupsonthesamesideson

theoppositesidesofthedoublebond.Prefixcis-trans-2.NamingbytheE,ZNotationalsystemTodisubstitutedAlkenes:E,ZNotationalsystembaseonanSequenceRule

（次序规则）－Cahn-Ingold-PrelogpriorityRuleConsideringeachofthedouble-bondedcarbon,identifythetwoatomsdirectlyattachedandrankthemaccordingtoatomicnumber.Br>Cl,C>HLowpriorityHighpriorityEconfiguration:thehigh-prioritygroupsareontheoppositesidesofthedouble-bond(E)-1-Bromo-1-chloro-1-butene(E)-1-氯-1-溴-1-丁烯LowpriorityHighpriorityZconfiguration:thehigh-prioritygroupsareonthesamesidesofthedouble-bond2.Whentwoatomsdirectlyattachedtothedoublebondareidentical,lookatthesecond,third,orfourthatomsawayfromthedouble-bondedcarbonsuntilthefirstdifferenceisfound.(Z)-3-methyl-2-hexene(Z)-3-甲基-2-己烯<><3.Multiple-bondedatomsareequivalenttothesamenumberofsingle-bondedatoms.ThecarbonisbondedtoH,O,OThecarbonisbondedtoH,C,C3.4PhysicalPropertiesofAlkene3.4.1.TheConceptofDipoleMoment（,偶极矩:)Thedipolemoment,

isdefinesdasthemagnitudeofthechargeqateitherendofthemoleculardipoletimesthedistancerbetweenthecharges,

=qr,and

expressedindebyes(D).=

0.35,0.35~0.37,0.33,0D3.4.2TheRelationshipBetweenandb.pofConstitutionalIsomer=0.33D,0D,1.85D,0Db.p

=4oC,1oC,60.3oC,48.4oCForconstitutionalisomer(especially,forZandE),↑,b.p↑;Forconstitutionalisomer:m.p:E>ZOrganicReactions:Thebrokenoforiginalbonds,theformationofnewbonds.Startingmaterial（原料）Substrate（底物）Reagent（试剂）ProductReactantsAcovalentbondmaybreakintwoway:Homolyticbondbreak(Radical)(均裂)Heterolyticbondbreak(Polar)(异裂)CCl4solvent3.4Reactionalsitesofalkene:Theπbondisactiveandisreadilyattackedbysomereagents.Additionreactionα-Hiseasilylost3.4.1.ElectrophilicAdditionofAlkenes（亲电加成反应）

πelectronslieaboveandbelowtheplaneofdoublebond,soπ-bondedelectronsareexposed(裸露).π-bondTheπbondisattackedbyelectron-seekingreagents－Electrophile

（亲电试剂）Anreactionrule:Electronegativespecies+Electropositivespecies(1)AdditionofHydrogenHalides

(卤化氢)

toAlkenes

AlkanehalideHalogenHalideHalo卤素卤化物取代基FluorineFluorideFluoroChlorineChlorideChloroBromineBromideBromoIodineIodideIodo2-Butene2-ChlorobutaneOrientationofelectrophilicaddition:

Markovnikov’sRuleAdditiontoanunsymmetricallysubstitutedalkenes:

Markovnikov’sRule:IntheadditionofHXtoanalkene,theHattachestothecarbonwithfeweralkylgroupsandXattachestothecarbonwithmorealkylgroups.(80%)(20%)VladimirVassilyevichMarkovnikov1838-1904MechanismoftheReaction:Step1.Theformationofthecarbocation(正碳离子)ReactiveintermediateStep2.Theformationofthecarbocationistherate-determiningstep.slowfastThestabilityofcarbocations:Theonereasonthatstabilizeacarbocation:theelectron-donatingeffectofalkylgroups.Thestructureofcarbocations:+120°Thepositivelychargecarbonatomissp2-hybridized,Theporbitalisvacant.Thecarbocationistrigonalplane.Tertiary(3)>Secondary(2)>primary(1)>MethylTheStructureandStabilityofCarbocationThetrivalentcarbonissp2-hybridizedandhasavacantporbitalextendingperpendiculartotheplaneofthecarbonandthreeattachedgroups.σ-pσ-pσ-πTheStructureandStabilityofCarbonRadicalRegioselectivity(区域选择性)ofthereactionThereactionthatcanproceedinmorethanonedirection,butactuallyinwhichonedirectionispreferred.Regiospecific(区域专一的)Amorehighlysubstitutedcarbocationismorestablethanalesshighlysubstitutedone.+δ+δ+Theelectron-donatingorelectron-withdraweffectofagroupthatistransmittedthroughσbond.Inductiveeffect(诱导效应)ofsubstituents:Explanationfor“Markovnikov’srule”(I)(II)Thestabilitiesofcarbocation:(I)>(II)Electrophilicadditiontoanunsymmetri-callysubstitutedalkenegivethemorehighlysubstitutedcarbocation.CarbocationRearrangements(重排)(40%)(60%)HClCl-(I)(II)Cl-StabilitiesofC+:Tertiary>SecondaryHydride-shift0℃Problem:Proposeamechanismtoaccountforthefollowingresult:Reactivity:HI>HBr>HCl>>HFBasedontheabilitytoproton-donatingofHXAlkenes?Peroxide

effect(过氧化物效应)

AnunsymmetricalkenereactswithHBrinthepresentofaperoxide(R-O-O-R),theAnti-Markovnikovadditionoccurs.Free-radicaladdition（过氧化乙酰）（过氧化苯甲酰）TheMechanismforAnti-MarkovnikovAdditionofAlkenes

Why?Route1Route2(2)AdditionofSulfuricacidtoAlkenesColdConcentratedH2SO4AlkylhydrogenSulfate(硫酸氢酯)Hydration(水合反应)Mechanism:(3)Acid-catalyzedHydrationofAlkenes(酸催化的烯烃水合反应)(4)Hydroboration-Oxidation(硼氢化-氧化)ofalkenes

Themethodforpreparationofthealcoholsfromanti-Markov.Addition.Thehydroxylgroupwasaddedonlesssubstitutedcarbon.Organoboranes(有机硼烷)HerbertCharlesBrownGotthe1979NobelprizeMajormethodtopreparealcoholsinindustryCatalyst:DiluteH2SO4,H3PO4Hediscoveredthehydroborationreaction(additionofdiboranetoalkenes)anddevelopedthemulti-facetedandsyntheticallyusefulchemistryoftheresultingorgano-boranes.Inthisphoto,ProfessorBrownholdsamodelof9-borabicyclo[3.3.1]nonane(9-BBN),preparedbyaddingboraneto1,5-cyclooctadieneanditselfastable,usefulhydroboratingreagent.ThisworkissummarizedinBrown'sbook"OrganicSynthesisviaBoranes"(1975).Browncontri-butedtomanyotherareasoforganicchemistry,amongwhichwereselectivereducingagents,stericeffects(indisplacement,eliminationandacid-basereactions),anddirectiveeffectsinelectrophilicaromaticsubstitution(theσ+constant).Brownisperhapsthemostprolificorganicchemistofthe20thcentury.Heisbestknownforhisworkinorganoboronchemistry,forwhichheshared(withG.Wittig)the1979NobelPrizeinChemistry.(5)

Hydroboration-Oxidation(硼氢化反应):organoboraneboraneOrganoboranesSterichindranceFeatureofhydroboration-oxidation:1.Regioselectivity:followingMarkov.Rule.2.Stereochemistry:Syn-addition（顺式加成）

:Twoatomsorgroupsaddtothesamefaceofadoublebond.trans-2-Methylcyclo-pentanol3.NonrearrangementSyn-additionAnti-addition（反式加成）

:Twoatomsorgroupsaddtotheoppositefacesofadoublebond.ThestereoselectivityofHydroboration-Oxidation:Problem:Whatproductswouldyouobtainfromreactionof1-ethylcyclopentenewithBH3,followedbyH2O2,OH-?(6)Solvomercuration/reduction(溶剂汞化/还原反应：羟汞化-脱汞反应）(7)AdditionofHalogentoAlkenes0℃Vicinaldihalide(邻二卤代物)Solvents:CH2Cl2,CHCl3,AceticacidIdentificationforC=C.Reagents:Cl2,Br2.Mechanismofthereaction:Step1.Step2.Bromo-anionattacksfromsideopposite.Step1istherate-determiningstep.Bromoniumion(型离子)Step1.Step2.StereochemistryofhalogenadditionAnti-addition(8)ConversionofAlkenestoVicinalHalohydrin(邻卤代醇)β-HalohydrinAdditionofhalogeninaqueoussolution.Mechanismofthereaction:Featuresofthereaction:FollowingMarkov.Rule,equaltotheadditionofonemoleofHO-Cl+(次氯酸)2.Anti-addition3.4.2HydrogenationofAlkenes+heatCatalyst:Pt(platinum),Pd(palladium),Ni(nickle)Featuresofthereaction:1.Anexothermicreaction（放热反应）Broken:πbond,H-HσbondFormation:2C-HσbondHeatofhydrogenation:Theheatevolvedonhydrogenationofonemole.ofanalkene.Thehigheristheheatofhydrogenation,thelessstableisthealkene.Theheatofhydrogenationisrelativetothestabilityofalkenes.Stabilityofalkenes:Cis-<Trans-Mechanismofalkenehydrogenation2.TheroleofthemetalcatalystVeryslowlywithoutcatalyst.Changingthereactionpathtoloweractivationenergy（活化能）.Theadditionofhydrogentoalkeneiscatalytichydrogenation（催化氢化）.3.StereochemistryofAlkenehydrogenationAlkenehydrogenation:syn-addition

（顺式加成）CatalystHydrogenabsorbedoncatalystsurfaceComplexofalkenetocatalystMechanismofalkenehydrogenationInsertionofhydrogenintoC=CAlkaneproductRegeneratedcatalystH2HHHHHH+4.Heterogeneousreaction

（异相反应）Solvent（溶剂）：ethanol,hexaneoraceticacid.TodissolveaalkeneMetal:solidThereactionoccursattheinterfaceoftwophase.Homogeneous(均相）

3.4.3OxidationofAlkenes(1)EpoxidationofAlkenes(环氧化反应)Peroxyacid(过氧酸)Epoxide(环氧化物)Sharpless,K.B.gotthe2001Nobelprize.Mechanism:Reagent:

Peroxyaceticacid(过氧乙酸)K.BarrySharpless,Ph.D.

Organic/InorganicChemist

TheScrippsResearchInstitute

/chem/sharpless/cv.html(2)Hydroxylation(羟基化反应)ofalkenes:Alkenesreactwithpotassiumperman-ganateorOsmiumtetraoxideinbasicsolutiontoform1,2-diols(glycol)(二醇).Cyclohexenecis-cyclohexanediol(37%)synstereochemistry.ColdsolutionofNaOH:Lowertemperarue<10oC(3)Oxidativecleavageofalkenes:(A)OzonolysisofAlkenes(臭氧化反应)O3(ozone)Reducingagent:ZnMechanism:Mechanism:Identificationtothestructureofaalkene2-Methyl-2-buteneAcetoneAcetaldehyde(B)WithKMnO4solutionInhotOH-solution,neutraloracidicsolution:Isopr