有機化學Chapter3.Alkenes烯烴

Chapter3Alkenes3.1AlkeneNomenclature3.2StructureofAlkenes3.3IsomerisminAlkenes

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

3.4ReactionsofAlkenes

3.4.1ElectrophilicAdditionofAlkenes(烯烴親電加成）

(1)AdditionofHydrogenHalidestoAlkenes（烯烴與鹵化氫加成）

Orientationofelectrophilicaddition

（親電加成的方向）

MechanismoftheReaction（反應機理）

Thestabilityofcarbocations（碳正離子的穩(wěn)定性）

CarbocationRearrangements（碳正離子的重排）

Peroxideeffect（過氧化物效應）(2)AdditionofSulfuricacidtoAlkenes

（烯烴與硫酸加成）(3)Acid-catalyzedHydrationofAlkenes

(酸催化的烯烴水合反應)(4)Hydroboration-Oxidationofalkenes

（硼氫化-氧化反應）(5)AdditionofHalogentoAlkenes（與鹵素加成）

(6)ConversionofAlkenestoVicinalHalohydrin(鄰鹵代醇)3.4.2HydrogenationofAlkenes(烯烴的氫化反應）

Heatofhydrogenation（氫化熱）

Stabilitiesofalkenes（烯烴的穩(wěn)定性）

Mechanismofalkeneshydrogenation

（烯烴加氫的反應機理）

StereochemistryofAlkeneshydrogenation(烯烴加氫的立體化學)

Heterogeneousreaction（異相反應）3.4.3OxidationofAlkenes（烯烴的氧化）

(1)Epoxidationofalkenes（烯烴的環(huán)氧化）

(2)Hydroxylationofalkenes（烯烴的羥基化）

(3)Oxidativecleavageofalkenes:

（烯烴氧化斷鍵）

(A)Ozonolysisofalkenes（烯烴的臭氧化）

(B)WithKMnO4solution

（烯烴的高錳酸鉀氧化）3.4.4ReactionofAlkeneswithAlkenes:Polymerization（聚合反應）Alkenes:

(Olefin)Hydrocarboncontainingcarbon-carbondoublebondThesiteofreactionsThefunctionalgroup（反應部位）（官能團）AliphatichydrocarbonsSaturated(飽和烴)Unsaturated(不飽和烴)AlkanescycloalkanesAlkenesAlkynesP74Isobutylene（異丁烯）α- Pinene（α-蒎烯）3.1NomenclatureofAlkenesIUPACNames:1.Givethebasenamebyselectingthelongestcontinuouscarbonchainincludingthedoublebond.-ene

（某烯）2.Number:Givethedouble-bondcarbonsthelowernumber.3.Thelocationofsubstituentslikealkanes.4.WhenCnumberisover10:稱某碳烯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（異丙烯基）Methenecyclohexane（亞甲基環(huán)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分子的不飽和度(Degreeofunsaturation)只含碳、氫、氧、氮以及單價鹵素的計算公式：

Ω＝C＋1－(X－N)/2其中，C代表碳原子的數(shù)目，X代表氫和鹵素原子的總數(shù)，N代表氮原子的數(shù)目，氧和其他二價原子對不飽和度計算沒有貢獻，故不需要考慮氧原子數(shù)。這種方法只適用于含碳、氫、單價鹵素、氮和氧的化合物。補充理解說明：(1）若有機物為含氧化合物，因為氧為二價，C=O與C=C“等效”，所以在進行不飽和度計算時可不考慮氧原子。如CH2=CH2、CH3CHO、CH3COOH的不飽和度Ω為1。

2）有機物分子中的鹵素原子取代基，可視作氫原子計算不飽和度Ω。如：C2H3Cl的Ω為1，其他基團如-NH2、-SO3H等都視為氫原子。(3）有機物分子中含有N、P等三價原子時，每增加1個三價原子，則等效為減少1個氫原子。如，CH3NH2的不飽和度Ω=0。(4）C=C，C=N碳碳雙鍵的不飽和度Ω=1；碳碳叁鍵，C≡N的不飽和度Ω=2,環(huán)狀化合物的不飽和度Ω=1。不飽和度計算的用途先寫出分子式，然后根據(jù)分子式計算不飽和度，來推測分子中可能的雙鍵，三鍵或者環(huán)的個數(shù)。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

（次序規(guī)則）－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（,偶極矩:)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（試劑）ProductReactantsAcovalentbondmaybreakintwoway:Homolyticbondbreak(Radical)(均裂)Heterolyticbondbreak(Polar)(異裂)CCl4solvent3.4Reactionalsitesofalkene:Theπbondisactiveandisreadilyattackedbysomereagents.Additionreactionα-Hiseasilylost3.4.1.ElectrophilicAdditionofAlkenes（親電加成反應）

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

（親電試劑）Anreactionrule:Electronegativespecies+Electropositivespecies(1)AdditionofHydrogenHalides

(鹵化氫)

toAlkenes

AlkanehalideHalogenHalideHalo鹵素鹵化物取代基FluorineFluorideFluoroChlorineChlorideChloroBromineBromideBromoIodineIodideIodo2-Butene2-ChlorobutaneOrientationofelectrophilicaddition:

Markovnikov’sRuleAdditiontoanunsymmetricallysubstitutedalkenes:

Markovnikov’sRule:IntheadditionofHXtoanalkene,theHattachestothecarbonwithfeweralkylgroupsandXattachestothecarbonwithmorealkylgroups.(80%)(20%)VladimirVassilyevichMarkovnikov1838-1904MechanismoftheReaction:Step1.Theformationofthecarbocation(正碳離子)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(區(qū)域選擇性)ofthereactionThereactionthatcanproceedinmorethanonedirection,butactuallyinwhichonedirectionispreferred.Regiospecific(區(qū)域?qū)Ｒ坏?Amorehighlysubstitutedcarbocationismorestablethanalesshighlysubstitutedone.+δ+δ+Theelectron-donatingorelectron-withdraweffectofagroupthatistransmittedthroughσbond.Inductiveeffect(誘導效應)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(過氧化物效應)

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

Why?Route1Route2(2)AdditionofSulfuricacidtoAlkenesColdConcentratedH2SO4AlkylhydrogenSulfate(硫酸氫酯)Hydration(水合反應)Mechanism:(3)Acid-catalyzedHydrationofAlkenes(酸催化的烯烴水合反應)(4)Hydroboration-Oxidation(硼氫化-氧化)ofalkenes

Themethodforpreparationofthealcoholsfromanti-Markov.Addition.Thehydroxylgroupwasaddedonlesssubstitutedcarbon.Organoboranes(有機硼烷)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(硼氫化反應):organoboraneboraneOrganoboranesSterichindranceFeatureofhydroboration-oxidation:1.Regioselectivity:followingMarkov.Rule.2.Stereochemistry:Syn-addition（順式加成）

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

:Twoatomsorgroupsaddtotheoppositefacesofadoublebond.ThestereoselectivityofHydroboration-Oxidation:Problem:Whatproductswouldyouobtainfromreactionof1-ethylcyclopentenewithBH3,followedbyH2O2,OH-?(6)Solvomercuration/reduction(溶劑汞化/還原反應：羥汞化-脫汞反應）(7)AdditionofHalogentoAlkenes0℃Vicinaldihalide(鄰二鹵代物)Solvents:CH2Cl2,CHCl3,AceticacidIdentificationforC=C.Reagents:Cl2,Br2.Mechanismofthereaction:Step1.Step2.Bromo-anionattacksfromsideopposite.Step1istherate-determiningstep.Bromoniumion(型離子)Step1.Step2.StereochemistryofhalogenadditionAnti-addition(8)ConversionofAlkenestoVicinalHalohydrin(鄰鹵代醇)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（放熱反應）Broken:πbond,H-HσbondFormation:2C-HσbondHeatofhydrogenation:Theheatevolvedonhydrogenationofonemole.ofanalkene.Thehigheristheheatofhydrogenation,thelessstableisthealkene.Theheatofhydrogenationisrelativetothestabilityofalkenes.Stabilityofalkenes:Cis-<Trans-Mechanismofalkenehydrogenation2.TheroleofthemetalcatalystVeryslowlywithoutcatalyst.Changingthereactionpathtoloweractivationenergy（活化能）.Theadditionofhydrogentoalkeneiscatalytichydrogenation（催化氫化）.3.StereochemistryofAlkenehydrogenationAlkenehydrogenation:syn-addition

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

（異相反應）Solvent（溶劑）：ethanol,hexaneoraceticacid.TodissolveaalkeneMetal:solidThereactionoccursattheinterfaceoftwophase.Homogeneous(均相）

3.4.3OxidationofAlkenes(1)EpoxidationofAlkenes(環(huán)氧化反應)Peroxyacid(過氧酸)Epoxide(環(huán)氧化物)Sharpless,K.B.gotthe2001Nobelprize.Mechanism:Reagent:

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

Organic/InorganicChemist

TheScrippsResearchInstitute

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