有机化学英文chapter课件2

有机化学英文chapter(2)幻灯片本课件PPT仅供大家学习使用学习完请自行删除，谢谢！本课件PPT仅供大家学习使用学习完请自行删除，谢谢！AlkynesChapter7NomenclatureIUPAC:usetheinfix-yn-toshowthepresenceofacarbon-carbontriplebondCommonnames:prefixthesubstituentsonthetriplebondtotheword“acetylene〞Commonname:IUPACname:DimethylacetyleneVinylacetylene2-Butyne1-Buten-3-yneCycloalkynesCyclononyneisthesmallestcycloalkyneisolateditisquiteunstableandpolymerizesatroomtemptheC-C-Cbondangleaboutthetriplebondisapproximately155°,indicatinghighanglestrainPhysicalPropertiesSimilartoalkanesandalkenesofcomparablemolecularweightandcarbonskeletonAcidityThepKaofacetyleneandterminalalkynesisapproximately25,whichmakesthemstrongeracidsthanammoniabutweakeracidsthanalcohols(Section4.1)terminalalkynesreactwithsodiumamidetoformalkyneanionsAcidityterminalalkynescanalsobeconvertedtoalkyneanionsbyreactionwithsodiumhydrideorlithiumdiisopropylamide(LDA)becausewaterisastrongeracidthanterminalalkynes,hydroxideionisnotastrongenoughbasetoconvertaterminalalkynetoanalkyneanionAlkylationofAlkyneAnionsAlkyneanionsarebothstrongbasesandgoodnucleophilesTheyparticipateinnucleophilicsubstitutionreactionswithalkylhalidestoformnewC-Cbondstoalkylgroups;theyundergoalkylationbecausealkyneanionsarealsostrongbases,alkylationispracticalonlywithmethyland1°halideswith2°and3°halides,eliminationisthemajorreactionAlkylationofAlkyneAnionsalkylationofalkyneanionsisthemostconvenientmethodforthesynthesisofterminalalkynesalkylationcanberepeatedandaterminalalkynecanbeconvertedtoaninternalalkynePreparationfromAlkenesTreatmentofavicinaldibromoalkanewithtwomolesofbase,mostcommonlysodiumamide,resultsintwosuccessivedehydrohalogenationreactions(removalofHandXfromadjacentcarbons)andformationofanalkynePreparationfromAlkenesforaterminalalkenetoaterminalalkyne,3molesofbasearerequiredPreparationfromAlkenesasideproductmaybeanallene,acompoundcontainingadjacentcarbon-carbondoublebonds,C=C=CAhaloalkene(avinylichalide)AnalleneAnalkyneRCCCRRHRHXHNaNH2RC–C=CR-HBrCCCRRRHAlleneAllene:acompoundcontainingaC=C=Cgroupthesimplestalleneis1,2-propadiene,commonlynamedalleneAllenesmostallenesarelessstablethantheirisomericalkynes,andaregenerallyonlyminorproductsinalkyne-formingdehydrohalogenationreactionsAdditionofX2AlkynesaddonemoleofbrominetogiveadibromoalkeneadditionshowsantistereoselectivityAdditionofX2theintermediateinbrominationofanalkyneisabridgedbromoniumionAdditionofHXAlkynesundergoregioselectiveadditionofeither1or2molesofHX,dependingontheratiosinwhichthealkyneandhalogenacidaremixed2,2-Dibromopropane2-BromopropenePropyneCH3CCHBrBrBrHBrCH3C=CH2CH3CCH3HBrAdditionofHXtheintermediateinadditionofHXisa2°vinyliccarbocationreactionofthevinyliccation(anelectrophile)withhalideion(anucleophile)givestheproductAdditionofHXintheadditionofthesecondmoleofHX,Step1isreactionoftheelectronpairoftheremainingpibondwithHBrtoformacarbocationofthetwopossiblecarbocations,thefavoredoneistheresonance-stabilized2°

carbocationHydroborationAdditionofboranetoaninternalalkynegivesatrialkenylboraneadditionissynstereoselectiveHydroborationtopreventdihydroborationwithterminalalkynes,itisnecessarytouseastericallyhindereddialkylborane,suchas(sia)2BHtreatmentofaterminalalkynewith(sia)2BHresultsinstereoselectiveandregioselectivehydroborationHydroborationTreatinganalkenylboranewithH2O2inaqueousNaOHgivesanenolenol:

acompoundcontaininganOHgroupononecarbonofacarbon-carbondoublebondanenolisinequilibriumwithaketoformbymigrationofahydrogenfromoxygentocarbonandthedoublebondfromC=CtoC=Oketoformsgenerallypredominateatequilibriumketoandenolformsare

tautomers

andtheirinterconversioniscalledtautomerismHydroborationhydroboration/oxidationofaninternalalkynegivesaketonehydroboration/oxidationofaterminalalkynegivesanaldehyde3-Hexanone3-Hexyne1.

BH32.

H2O2,

NaOHOAdditionofH2O:hydrationInthepresenceofsulfuricacidandHg(II)salts,alkynesundergoadditionofwater+Propanone(Acetone)1-Propen-2-ol(anenol)PropyneCH3CCHOHOHgSO4H2SO4H2OCH3C=CH2CH3CCH3AdditionofH2O:hydrationStep1:attackofHg2+(anelectrophile)onthetriplebond(anucleophile)givesabridgedmercuriniumionStep2:attackofwater(anucleophile)onthebridgedmercuriniumionintermediate(anelectrophile)opensthethree-memberedringAdditionofH2O:hydrationStep3:protontransfertosolventgivesanorganomercuryenolStep4:tautomerismoftheenolgivestheketoformAdditionofH2O:hydrationStep5:protontransfertothecarbonyloxygengivesanoxoniumionSteps6and7:lossofHg2+givesanenol;tautomerismoftheenolgivestheketoneReductionTreatmentofanalkynewithhydrogeninthepresenceofatransitionmetalcatalyst,mostcommonlyPd,Pt,orNi,convertsthealkynetoanalkaneReductionWiththeLindlarcatalyst,reductionstopsatadditionofonemoleofH2

thisreductionshowssynstereoselectivityHydroboration-ProtonolysisAdditionofboranetoaninternalalkynegivesatrialkenylboraneadditionissynstereoselectivetreatmentofatrialkenylboranewithaceticacidresultsinstereoselectivereplacementofBbyHDissolvingMetalReductionReductionofanalkynewithNaorLiinliquidammoniaconvertsanalkynetoanalkenewithantistereoselectivityDissolvingMetalReductionStep1:aone-electronreductionofthealkynegivesaradicalanionStep2:thealkenylradicalanion(averystrongbase)abstractsaprotonfromammonia(averyweakacid)DissolvingMetalReductionStep3:asecondone-electronreductiongivesanalkenylanionthisstepestablishestheconfigurationofthealkeneatransalkenylanionismorestablethanitscisisomerStep4:asecondacid-basereactiongivesthetransalkene+NaRCCRHRCCRH+Na+Analkenylanion.:OrganicSynthesisAsuccessfulsynthesismustprovidethedesiredproductinmaximumyieldhavethemaximumcontrolofstereochemistryandregiochemistrydominimumdamagetotheenvironment(itmustbea“green〞synthesis)OurstrategywillbetoworkbackwardsfromthetargetmoleculeOrganicSynthesisWeanalyzeatargetmoleculeinthefollowingwaysthecarbonskeleton:howcanweputittogether.OuronlymethodtodateforformingnewaC-