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1、Chapter7AlkynesandDienes§7-1AlkynesGeneralformula:CHn2n-2UnsaturatedhydrocarbonsThecarbon-carbontriplebond(C≡C)isthefunctionalgroupofalkynes.LiketheC=Cbond,theC≡Cbondishighlyreactiveandreactswithmanyofthesamereagentsthatreactwiththedoublebondsofalkenes.I.Structure,is
2、omerismandnomenclature:σππspHCCHcarbonskeletonsIsomerismpositionofthetriplebondThenomenclaturerulesareexactlythesameasforthenamingofalkenes,exceptthattheending–ynereplaces–ene.HCCHHCCCH3HCCC2H5AcetyleneMethylacetyleneEthylacetyleneEthynePropyne1-ButyneCH3CCCH3CH3CCCH
3、(CH3)2DimethylacetyleneIsopropylmethylacetylene2-Butyne4-Methyl-2-pentyneHCCHCH3CHCCCH2CH3CCH3CH2CCH3CH35-甲基-3-庚炔(E)-3-甲基-3-戊烯-1-炔CH3CCCHCH2CH3CHCHCH2CCCH31-戊烯-3-炔2-庚烯-5-炔II.PhysicalpropertiesofalkynesSimilarwiththephysicalpropertiesofthealkanesandalkenes.Lowpolarity
4、.Insolubleinwater,butquitesolubleinlowpolarsolvents.Lessdensethanwater.Theirboilingpointsshowtheusualincreasewithincreasingcarbonnumber,andtheusualeffectsofchain-branching.III.ChemicalpropertiesofalkynesReactionsthattakeplaceatthetriplebond——addition(availabilityofth
5、elooselyheldπelectrons).YZYZCC+YZCCCCYZYZReactionsthatareduetotheacidityofahydrogenatomheldbytriplybondedcarbon——reactionsasacids.CCH+baseCC1.AcidityofterminalalkynesNaNH2RCCHRCC-Na++NH3liq.NH3pKa2636110oCHCCH+NaHCCNa+1/2H2200oCHCCH+2NaNaCCNa+H2CH3CCH+C2H5MgBrCH3CCMg
6、Br+C2H6CH3CCH+n-C4H9LiCH3CCLi+n-C4H10HCCH+2Ag(NH3)2NO3AgCCAg+2NH4NO3+2NH3HCCH+2Cu(NH3)2ClCuCCCu+2NH4Cl+2NH3Preparationofalkynes:1o2.Additionreactions(1)AdditionofhydrogenSyn-additionH2RR'CCSynLindlarcatalystHHRCCR'NaorLiRHCCAntiNH3(liq)HR'Highlystereoselective!(2)Add
7、itionofhalogensX2XX2XXCCCCCCXXXX2=Cl2,Br2Br2C2H5BrC2H5CCC2H5CC90%BrC2H5Anti-additionBr2CH2CHCH2CCHCH2CHCH2CCHBrBr(3)AdditionofhydrogenhalidesXHXHXHXCCCCCCHHXOrientationisMarkovnikov.HBrHBrBrCH3CCHCH3CCH2CH3CCH3BrBrHClC2H5ClC2H5CCC2H5CC97%HC2H5Anti-addition76%(4)Addit
8、ionofwater(Hydration)H2SO4fastHCC+H2OCCCCHgSO4HOHHOEnolH2SO4OHCCH+H2OHCCHCH3CHHgSO4HOHH2SO4OCH3CCH+H2OCH3CCHCH3CCH3HgSO4OHHH2SO4OCH
