4清华大学有机化学李艳梅老师课件第四章

Cycloalkanes第四章环烷烃OrganicChemistryA(1)ByProf.LiYan-MeiTsinghuaUniversityContent4.1Classification,Isomerizationandnomenclature4.2Structureofcycloalkanes4.3Physicalproperties&spectrumdata4.4Chemicalproperties4.5Preparation(learnonyourown)4.1Classification,Isomerizationandnomenclature4.1.1Classification4.1.2Isomerism4.1.3Nomenclature4.1.1ClassificationBythesizeofthering按环的大小SmallringsMediumringsCommonringsLargeringsC3~C4C8~C12C5~C7C13~Bythesaturation按不饱和度CnH2nCnH2n-2CnH2n-4Cycloalkanes环烷Cycloolefines环烯Cycloalkynes环炔Monocycliccompounds单环Bythenumberoftherings按环的数目Polyringcompounds多环Fusedring稠环Bridgedring桥环Spirorings螺环两环之间共用一个碳原子两环之间共用一根共价键（共用两个直接相连的碳原子）两环之间共用两个不直接相连的碳原子螺原子桥头碳Todefinethenumberoftherings:Thenumberofcuttingyouneedtogetachainmoleculeoutofapolyringcompound几环？将桥（稠）环烃变为链状化合物时需要断裂的碳链数。如需断裂两次，则为二环化合物，断裂三次则为三环化合物。SomeinterestingbridgingcompoundsCubane立方烷Primane棱烷Diamentane金刚烷篮烷4.1.2IsomerismConstitutionalisomersarederivatedfromthechangeofsizeofringsandlengthofsidechainsC5H10环的大小及侧链长短与位置变化4.1.3Nomenclature命名4.1.3.1Monocyclicalkane单环烷烃1,Whenthesidechainisnotverycomplicate:当支链不复杂时，以环烷烃为母体methylcyclopentane2-ethyl-4-methyl-1-propylcycloheptane1-ethyl-3-methylcyclopentane1,2-dimethylcyclopentane1,2-二甲基环戊烷甲基环戊烷1-甲基-3-乙基环戊烷4-甲基-3-乙基-1-丙基环己烷2,Whenthesidechainiscomplicateordifficulttoname:当支链较复杂或不易命名时，以环烷基为取代基3-cyclohexylhexane3-环己基己烷3,Whentworingsareconnected两环相连时Cyclopropylcyclohexane环丙基环己烷Cyclopropylcyclopropane环丙基环丙烷4,Cisandtransisomerism:CH3CH3HHCH3HCH3HCH3CH3CH3CH3Cis-1,4-dimethylcyclohexaneTrans-1,4-dimethylcyclohexaneHowtonamethiscompound?CH3CH3CH34.1.3.2Polyringalkane多环烷烃1,Spirocycloalkanes螺环烃1）选母体：根据成环的总碳原子数，称为“螺某烷”。2）编号：从小环开始；从第一个非螺原子开始。3）书写：先写词头“螺”方括号内沿着编号方向写出每个环中除螺原子外的每个环的碳原子数数字之间用圆点隔开最后写出包括螺原子在内碳原子数的烷烃名称12345678910螺[4.5]癸烷1“小原则”：在不违背螺环烃命名的“大”原则基础上，在编号时应尽可能令取代基的位号最小。123456789101-甲基螺[4.5]癸烷思考！6-甲基螺[4.5]癸烷---yrg12345678910spiro[4.5]decane螺[4.5]癸烷spiro[5.5]undecane螺[5.5]十一烷123456789106-methylspiro[4.5]decane6-甲基[4.5]癸烷4-methylspiro[2.4]heptane4-甲基[2.4]庚烷1）选母体：根据成环的总碳原子数及环数，称为“n环某烷”。2）编号：从桥头碳开始；从最长桥开始。3）书写：先写环数方括号内沿着编号方向写出每个环中除桥头碳原子外的每个环的碳原子数数字之间用圆点隔开最后写出包括桥头碳原子在内碳原子数的烷烃名称2,Bridged-ringalkaneandfused-ringalkane桥环烃和稠环烃12345678bicyclo[3.2.1]octane二环[3.2.1]辛烷2,7,7-trimethylbicyclo[2.2.1]heptanebicyclo[1.1.0]butane2,7,7-三甲基二环[2.2.1]庚烷注意：有两个桥头碳可供选择二环[1.1.0]丁烷Forpolycycliccompoundasfollowing多元环Decidingthemainring选“主环”：最大的环Choosingthemainbridgedcarbon选“主桥头碳”：主环与非主环的最长桥共用的桥头碳Decidetheserialnumber编号：从主桥头碳开始；从最长桥开始Namingthecompound书写（注意与非主桥相连的桥需注明所连桥的编号）1234567Tricyclic[2.2.1.02.6]heptane书写（注意与非主桥相连的桥需注明所连桥的编号）02.6表示桥所连的碳的序号为2、6-----YRG思考：12345678910Tricyclic[3.2.2.12.7]decanetricyclic[3.2.2.12.7]dacaneFusedringnaphthaleneHydrogenatednaphthaleneEndo/exaOHHendoHOHexa区别：母体！4.2.1Baeyer’sstraintheory4.2.2Heatofcombustionforcycloalkane4.2.3Currentopinions4.2.4Conformationsofcyclohexane4.2.5Configurationofdecalin4.2StructureofcycloalkanesBefore18801883Onlypentaringsandhexaringswerefound.Itwasregardedthatringssmallerthanpentaringsandbiggerthanhexaringsdonotexist,orarenotstable.W.H.PerkinsynthesizedC3,C4,andidentifiedtherelativereactivity:doublebondC3C4,whileC5andC6ringsarerelativelymorestable.1885A.von.Baeyerputforwardthestraintheory4.2.1Baeyer’sstraintheoryBayer’s张力学说Assumption:1,carbonatomsintheringareonthesameplane;成环的碳原子均在同一同面上，且呈正多边形2,carbonatomsaresp3carbonatoms;碳原子采取sp3杂化形式，正常键角应为约109.5度3,tomeetsomespecialanglesinthering,thebondshavetobebending;为了满足平面正多边形的内角要求，成环的键必须向内或向外“屈挠”，“屈挠”的程度越大，体系越不稳定。MorebendingMoreanglestrainHigherenergyLessstability60o90o108o120o129oMoststable?可解释一些体系的稳定性特点，但还有一些体系无法解释。4.2.2HeatofcombustionforcycloalkaneHeatofcombustionperCH2kJ/mol697686664659662n658Donotfitthestraintheory!角张力（Baeyer张力）扭转张力范氏力影响环体系稳定性的主要因素：4.2.3CurrentopinionsCCC105.5oCCCBentBond（弯曲键、香蕉键）角张力：109.50-105.50=4012HHHH12CH233扭转张力：三组H－C－C均处于全重叠式三元环yrg蝴蝶状蝴蝶式HHHHHHHHHHHHHHHH1234Anonplanarconformation非平面构象也存在弯曲键111.50角张力：111.50－109.50=20123HHH2CH2CHH4部分交叉式扭转张力较小四元环yrg6.3kJ/molhigher全重叠式2.5kJ/molenvelopstructurehalf-chairstructure信封式半椅式五元环yrg如果：具有多组全重叠式六元环yrgLargering多于13个碳原子的环体系中，分子链一般呈皱折形StrainenergyincycloalkanesNameAnglestrainTwiststrainVandewaalsC3GreatMediumNoC4GreatMediumNoC5SlightMediumNoC6NoNoNoC7~C12MediumMediumGreatC12~NoNoNo4.2.4ConformationsofcyclohexaneYearNameofscientistPointofview1883BaeyerAssumesthatsixcarbonatomsareonthesameplane1890H.SachseTwoconformationsmayexist1915-1918W.M.MohrChairmodelandboatmodel1920Cyclohexanewasprovedtobenonplanarexperimentally1943O.HasselChairmodelismoststable(electrondiffractionmethod)1950D.BartonConformationanalysisofcyclohexaneAhistory4.2.4.1Conformationofcyclohexane250pmC350pmChairStructure椅式123456123HHH2CCH2HH465HHHH部分交叉式，扭转张力较小AxialbondEquatorialbondTwotypesofC-Hbondsinchairstructurea键e键轴与轴平行yrg与所在平面几乎垂直yrga键e键Boatstructure船式结构183pmVandewaalradiusofHatomis120pm,sothetwoadjacenthydrogenatomscausesseriousexcluding.存在范氏力123456HHHH651HH2CHHHH2C423全重叠式，存在扭转张力2、3、5、6碳处于同一平面FlagpoleinteractionTwistboatstructure扭船式HHHHHHHHHHHH123456123456123456Halfchairstructure半椅式123456123456Potenti