參考講稿詳解org chem lecture30第pengfeili

Chapter16Ethers,Epoxides,andNomenclatureofPhysicalpropertiesofSpectroscopyofSynthesisofReactionsofSynthesisofReactionsofSulfides2Chapter

EthersarecompoundsofformulaR-O-R',whereRandR'maybealkylgroupsoraryl(benzenering)groups.ThetwoalkylgroupsarethesameinasymmetricaletheranddifferentinanunsymmetricalThemostimportantcommercialetherisdiethylether,called"ethylether,“orsimplyAgoodsolventforreactionsandextractions.Avolatilestartingfluidfordieselandgasolineengines.Asurgicalanestheticforoverahundredyears(startingin Thecommonnomenclatureofethers,whichissometimescalledthealkylalkyletherNamingthetwoalkylgroupsonoxygenandaddingthewordethylmethyl

methylphenylether,甲基苯基醚，(苯甲醚Underthecurrentsystem,thealkylgroupsshouldbenamedinalphabeticalTheoldsystemnamedthegroupsinorder reasing原來(lái)名體系是按照兩個(gè)烷基取代基的復(fù)雜性來(lái)排序的，簡(jiǎn)單的thecurrentcommon:"tert-butylmethyl theoldercommonname,"methyltert-butylether"(or Chapter

NomenclatureofTheIUPACsystem,generallyusedwithmorecomplicatedethers,issometimescalledalkoxyalkane

Thecommonnameofanepoxideisformedbyadding"oxide"tothenameofthealk hatis環(huán)氧化物名：在烯烴的英文名字后面加“oxide”。中文名字稱(chēng)“環(huán)氧某烷”ethylene

cyclohexene cis-2,3-e順-2,3--5Anothersystematicmetho mesepoxidesasderivativesoftheparentcompound,ethyleneoxide,using"oxirane"asthesystematicnameforethyleneoxide.Theringatomsofaheterocycliccompoundarenumberedstartingwiththeheteroatomandgoinginthedirectiontogivethelowestsubstituentnumbers.Notethatthenumberingisdifferentforthe"epoxy"systemnames,whichnumberthelongestchainratherthanthering.

l,2-epoxy-l-methoxypropane6OxetanesThefour-memberedoxetanes.Morereactivethanlargercyclicethersandopen- hers.Notasreactiveasthehighlystrainedoxiranesepoxides)

FuransOxolanes)Thefive-memberedcyclicunsaturatedethers.

3甲氧基呋喃

四氫呋 Pyrans(Oxanes)Thesix-memberedcyclicunsaturatedethers.Thesaturatedcompound:fourmorehydrogenatoms,calledtetrahydropyran

DioxanesTwooxygenatomsinasix-memberedring：thetwooxygenatomsina1,4-1,4-Dioxaneismisciblewithwater,itiswidelyusedasapolarsolventfororganicreactions.1,4- 4-methyl-1,3- dibenzo-1,4-dioxane

1,4-二氧六環(huán)4-甲基-1,3-二氧六 二苯并-1,4-二氧六環(huán)2,3,7,8-四氯二苯并二氧六StructureandpolarityofEthersEthershaveabentstructure,withansp3hybridoxygenatomgivinganearlytetrahedralbondangle.Inatypicalether,thebulkofthealkylgroupsenlargesthebondangle.Ethersarestronglypolarcompounds.Thedipolemomentof heristhevectorsumoftwopolarC-Obonds,withasubstantialcontributionfromthetwolonepairsofelectrons.BoilingPointsofEthersTheboilingpointsofethersarelowerThanthoseofalcoholshavingsimilarmolecularweights.BoilingPointsofEthersEthersdohavelargedipolemoments,resultingindipole-dipoleattractions,buttheseattractionsappeartohaverelativelylittleeffectontheirboilingpoints.Thislargedifferenceresultsmostlyfromhydrogenbondinginthealcohols.EthersasPolarSolventsIdeallysuitedassolventsformanyorganicreactions:Theydissolveawiderangeofpolarandnonpolarsubstances,andtheirrelativelylowboilingpointssimplifytheirevaporationfromthereactionproducts.Nonpolarsubstancestendtobemoresoluble hersthaninalcoholsbecauseethershavenohydrogen-bondinworktobebrokenupbythenonpolarsolute.中非極性溶質(zhì)不需要破壞氫鍵作 EthersasPolarSolventsPolarsubstancestendtobenearlyassoluble hersasinalcoholsbecauseethershavelargedipolemomentsaswellastheabilitytoserveashydrogenbondacceptors.Ethersdonotsolvateanionsaswellasalcoholsdo.Substanceswithlarge,diffuseanions,suchasiodides,acetates,andotherorganicanions,tendtobemoresoluble hersolventsthansubstanceswithsmaller,harderanionssuchasfluorides.Grignardreagent)thatrequirepolarEthersarenonhydroxylic(nohydroxylgroup),Grignardreagent)thatrequirepolarComplexeswithElectrophilesGrignardreagentscannotformunless herispresent,possiblytoshareitslonepairsofelectronswiththemagnesiumatom.Thissharingofelectronsstabilizesthereagentandhelpskeepitinsolution.her'snonbondingelectronsalsostabilizeborane,BH3.TheBH3?THFcomplexiscommerciallyavailableasa1Msolution,easilymeasuredandtransferredlikeanyotherair-sensitiveliquidreagent.可以穩(wěn)定硼B(yǎng)H3。BH3?THF絡(luò)合物的BorontrifluorideisusedasaLewisacidcatalystinawidevarietyofreactions.三氟化硼通常用作路易斯酸催化劑 herComplexes hers:largecyclicpolyethersthatspecificallysolvatemetalcationsbycomplexingthemetalinthecenterofthering.絡(luò)合在環(huán)位置，因此可以溶解Differentcrownetherssolvatedifferentcations,dependingonrelativesizesofthecroherandthecationandthenumberofbindingsitesaroundthecation.Complexationbycrohersoftenhelpspolarinorganicsaltstodissolveinnonpolarorganicsolvents.Thisenhancedsolubilityallowspolarsaltstobeusedunderaproticconditions,where plexedanionsmayshowgreatlyenhancedreactivity. InfraredSpectroscopyofEthersInfraredspectradonotshowobviousorreliableabsorptionsforethers.Ifthemolecularformulacontainsanoxygenatom,thelackofcarbonylorhydroxylabsorptionsintheIRsuggests MassSpectrometryofEthersThemostcommonfragmentationofethersiscleavagenexttooneofthecarbonatomsbondedtooxygen.acleavage.Anothercommoncleavageisthelossofeitherofthetwoalkylgroupstogiveanotheroxoniumionor kylcation.ProposeafragmentationtoaccountforeachnumberedpeakinthemassNMRSpectroscopyofEthers醚的核磁光Inthe1HNMRspectrum,protonsoncarbonatomsbondedtooxygenusuallyabsorbatchemicalshiftsbetweenδ3.5andδ4.氫譜:與氧原子相連的碳原子上氫質(zhì)子的 移在3.5ppm至4ppm之間Inthe13CNMRspectrum,acarbonatombondedtooxygenabsorbsbetweenδ65and 移在65ppm至90ppm之間IntheNMRspectrums,bothalcoholsandethershaveresonancesinthisrange.醇和醚的核磁光譜（氫譜和碳譜）很相似，特征IfacompoundcontainingC,H,andOhasresonancesinthecorrectrange,andifthereisnoO-HstretchorC=OstretchintheIR heristhemostlikelyfunctionalThe herSynthesisThemostreliableandversatileethersynthesisThismethodinvolvestheSN2attackof koxideiononanunhinderedpri halideortosylate.SecondaryalkylhalidesandtosylatesareoccasionallyusedintheWilliamsonsynthesis, iminationcompetes,andtheyieldsareoftenpoor.ThealkoxideiscommonlymadebyaddingNa,K,orNaHtotheWhyisthefollowingreactionapoormethodforthesynthesisoftert-butylpropylWhatwouldbethemajorproductfromthisreaction? Proposeabettersynthesisoftert-butylpropylether.ThedesiredSN2reactioncannotoccuronthetertiaryalkylhalide.Thealkoxideionisastrongaswellasanucleophile,andelimination AbettersynthesiswouldusethelesshinderedalkylgroupastheSN2substrateandthealkoxideofthemorehinderedalkylgroup.SynthesisofPhenylEthersAphenol(aromaticalcohol)canbeusedasthealkoxidefragment,butnotthehalidefragment,fortheWilliams hersynthesis. X

Page535，Problem16-ShowhowyouwouldusetheWilliams hersynthesistopreparethefollowingethers.Youmayuseanyalcoholsorphenolsasyourorganicstartingmaterials.Cyclohexylpropyl(c)1-methoxy-4-(e)Benzylt-butylether(benzyl=Ph-CH2-

OAlkoxymercuration-demercuration烷氧基化-脫化醚合成方IndustrialSynthesis:BimolecularDehydrationofAlcoholsIndustrialSynthesis:BimolecularDehydrationofAlcohols工業(yè)合成：醇雙分子脫水Bimoleculardehydrationisusedinindustrytomakesymmetricalethersfrompri Becausethedehydrationissolimitedinitsscope,itfindslittleuseinthelaboratorysynthesisofethers.水的范圍是非常有限的，在很少用于合成醚Ethersareunreactivetowardmostbases,buttheycanreactunderacidicconditions.EthersarecleavedbyheatingwithHBrorHItogivealkylbromidesoralkyliodides.Aprotonatedethercanundergosubstitutionoreliminationwith coholservingasaneutralleavinggroup.EthersreactwithconcentratedHBrandHIbecausethesereagentsaresufficientlyacidictoprotonatetheether,whilebromideandiodidearegoodnucleophilesforthesubstitution.Undertheseconditions,thealcoholleavinggroupusuallyreactsfurtherwithHXtogiveanotheralkylhalide.由可以作為中性離去基團(tuán)，質(zhì)子化的醚可發(fā)生取代或消除反應(yīng)。醚可與濃氫溴酸和ThisreactionconvertsadialkyletherintotwoalkylThemoleculemustnotcontainanyacid-sensitivefunctionalIodideandbromideionsaregoodnucleophilesbutweakbases,sotheyaremorelikelytosubstitutebytheSN2mechanismthantopromoteeliminationbytheE2mechanism.E2Step1:Protonationoftheethertoformagoodleavinggroup.

Step2:SN2cleavageoftheprotonatedStep3:Conversionofthealcoholfragmenttothealkylhalide.(Doesnoto