清华大学有机化学李艳梅老师第四章

1、.Cycloalkanes第四章第四章 环烷烃环烷烃Organic Chemistry A (1)By Prof. Li Yan-MeiTsinghua University 4.1 Classification, Isomerization and nomenclature 4.2 Structure of cycloalkanes 4.3 Physical properties & spectrum data 4.4 Chemical properties 4.5 Preparation (learn on your own) 4.1 Classification, Isomeri

2、zation and 4.1 Classification, Isomerization and nomenclaturenomenclature 4.1.1 Classification 4.1.2 Isomerism 4.1.3 Nomenclature4.1.1 ClassificationBy the size of the ring 按环的大小按环的大小Small ringsMedium ringsCommon ringsLarge ringsC3C4C8C12C5C7C13By the saturation 按不饱和度按不饱和度CnH2nCnH2n-2CnH2n-4Cycloalk

3、anes 环烷环烷Cyclo olefines 环烯环烯Cyclo alkynes 环炔环炔Monocyclic compounds 单环单环By the number of the rings 按环的数目按环的数目Polyring compounds 多环多环Fused ring 稠环稠环Bridged ring 桥环桥环Spiro rings 螺环螺环两环之间共用一个两环之间共用一个碳原子碳原子两环之间共用一根共两环之间共用一根共价键（共用两个直接价键（共用两个直接相连的碳原子）相连的碳原子）两环之间共用两个两环之间共用两个不直接相连的碳原不直接相连的碳原子子螺原子桥头碳To define

4、 the number of the rings:The number of cutting you need to get a chain molecule out of a poly ring compound几环？将桥（稠）环烃变为链状化合物时需要断裂的碳链将桥（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。为三环化合物。Some interesting bridging compoundsCubane立方烷立方烷Primane棱棱 烷烷Diamentane金刚烷金刚烷篮篮 烷烷4.1.2 Is

5、omerism Constitutional isomers are derivated from the change of size of rings and length of side chainsC5H10环的大小及侧链长短与位置变化环的大小及侧链长短与位置变化4.1.3 Nomenclature 命名命名4.1.3.1 Monocyclic alkane 单环烷烃单环烷烃1, When the side chain is not very complicate: 当支链不复杂时，以环烷烃为母体当支链不复杂时，以环烷烃为母体methylcyclopentane2-ethyl-4-me

6、thyl-1-propylcycloheptane1-ethyl-3-methylcyclopentane1,2-dimethylcyclopentane1,2-二甲基环戊烷二甲基环戊烷甲基环戊烷甲基环戊烷1-甲基甲基-3-乙基环戊烷乙基环戊烷4-甲基甲基-3-乙基乙基-1-丙基环己烷丙基环己烷2, When the side chain is complicate or difficult to name: 当支链较复杂或不易命名时，以环烷基为取代基当支链较复杂或不易命名时，以环烷基为取代基3-cyclohexylhexane3-环己基己烷环己基己烷3, When two rings are

7、 connected 两环相连时两环相连时Cyclopropylcyclohexane环丙基环己烷环丙基环己烷Cyclopropylcyclopropane环丙基环丙烷环丙基环丙烷4, Cis and trans isomerism:CH3CH3HHCH3HCH3HCH3CH3CH3CH3Cis-1,4-dimethylcyclohexaneTrans-1,4-dimethylcyclohexaneHow to name this compound ?CH3CH3CH34.1.3.2 Polyring alkane 多环烷烃多环烷烃1, Spiro cycloalkanes 螺环烃螺环烃123

8、456789101“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。12345678910思考！12345678910spiro4.5decane螺螺4.5癸烷癸烷spiro5.5undecane螺螺5.5十一烷十一烷123456789106-methylspiro4.5decane6-甲基甲基4.5癸烷癸烷4-methylspiro2.4heptane4-甲基甲基2.4庚烷庚烷2, Bridged-ring alkane and fused-ring alkane 桥环烃和稠环烃桥环烃和稠环烃12345678bicyclo3.2.1octane二环二环3.

9、2.1辛烷辛烷2,7,7-trimethylbicyclo2.2.1heptanebicyclo1.1.0butane2,7,7-三甲基二环三甲基二环2.2.1庚烷庚烷注意：有两个桥头碳可注意：有两个桥头碳可供选择供选择二环二环1.2.0丁烷丁烷For polycyclic compound as following 多元环多元环Deciding the main ring 选选“主环主环”：最大的环：最大的环Choosing the main bridged carbon 选选“主桥头碳主桥头碳”：主环与非主环的最长桥共用的桥头碳：主环与非主环的最长桥共用的桥头碳Decide the ser

10、ial number 编号：从主桥头碳开始；从最长桥开始编号：从主桥头碳开始；从最长桥开始Naming the compound 书写（注意与非主桥相连的桥需注明所连桥的编号）书写（注意与非主桥相连的桥需注明所连桥的编号）1234567Tricyclic2.2.1.02.6heptane思考：12345678910Tricyclic3.2.2.12.7decanetricyclic3.2.2.12.7dacaneFused ringnaphthaleneHydrogenated naphthaleneEndo/exaOHHendoHOHexa区别：母体！区别：母体！ 4.2.1 Baeyers

11、 strain theory 4.2.2 Heat of combustion for cycloalkane 4.2.3 Current opinions 4.2.4 Conformations of cyclohexane 4.2.5 Configuration of decalin4.2 Structure of cycloalkanesBefore 18801883Only penta rings and hexa rings were found. It was regarded that rings smaller than penta rings and bigger than

12、hexa rings do not exist, or are not stable.W.H.Perkin synthesized C3, C4, and identified the relative reactivity: double bond C3 C4 ,while C5 and C6 rings are relatively more stable.1885A.von.Baeyer put forward the strain theory4.2.1 Baeyers strain theory Bayers张力学说张力学说Assumption:1, carbon atoms in

13、the ring are on the same plane; 成环的碳原子均在同一同面上，且呈正多边形成环的碳原子均在同一同面上，且呈正多边形2, carbon atoms are sp3 carbon atoms; 碳原子采取碳原子采取sp3杂化形式，正常键角应为约杂化形式，正常键角应为约109.5度度3, to meet some special angles in the ring, the bonds have to be bending; 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”， “屈挠屈挠”的程度越

14、大，体系越不稳定。的程度越大，体系越不稳定。More bendingMore angle strainHigher energyLess stability60o90o108o120o129oMost stable?可解释一些体系的稳定性特点，但还有一些体系无法解释。 4.2.2 Heat of combustion for cycloalkane Heat of combustion per CH2kJ/mol697686664659662n658Do not fit the strain theory!p 角张力（Baeyer 张力）p 扭转张力p 范氏力影响环体系稳定性的主要因素： 4.

15、2.3 Current opinionsCCC105.5oCCCBent Bond （弯曲键、香蕉键）（弯曲键、香蕉键）角张力：角张力：109.50-105.50=4012HHHH12CH233扭转张力：扭转张力：三组三组HCC均处于全重叠式均处于全重叠式HHHHHHHHHHHHHHHHA nonplanar conformation 非平面构象非平面构象 也存在弯曲键也存在弯曲键 111.50角张力：角张力：111.50109.50 = 20123HHH2CH2CHH4部分交叉式部分交叉式扭转张力较小扭转张力较小6.3kJ/mol higher全重叠式全重叠式2.5kJ/molenvelop

16、 structurehalf-chair structure信封式 半椅式具有多组全重叠式具有多组全重叠式Large ring多于多于13个碳原子的环体系中，分子链一般呈皱折形个碳原子的环体系中，分子链一般呈皱折形Strain energy in cycloalkanesNameAngle strainTwist strainVan de waalsC3GreatMediumNoC4GreatMediumNoC5SlightMediumNoC6NoNoNoC7C12MediumMediumGreatC12NoNoNo4.2.4 Conformations of cyclohexaneYearN

17、ame of scientistPoint of view1883BaeyerAssumes that six carbon atoms are on the same plane1890H.SachseTwo conformations may exist1915-1918W.M.MohrChair model and boat model1920Cyclohexane was proved to be nonplanar experimentally1943O.HasselChair model is most stable(electron diffraction method)1950

18、D.BartonConformation analysis of cyclohexaneA history4.2.4.1 Conformation of cyclohexane250pmC350pmChair Structure 椅式椅式123456123HHH2CCH2HH465HHHH部分交叉式，扭转张力较小部分交叉式，扭转张力较小Axial bondEquatorial bondTwo types of C-H bonds in chair structurea 键键e 键键Boat structure 船式结构船式结构183pmVan de waal radius of H atom

19、is 120pm, so the two adjacent hydrogen atoms causes serious excluding.存在范氏力存在范氏力123456HHHH651HH2CHHHH2C423全重叠式，存在扭转张力全重叠式，存在扭转张力2、3、5、6碳处于同一平面碳处于同一平面Flagpole interactionTwist boat structure 扭船式扭船式HHHHHHHHHHHH123456123456123456Half chair structure 半椅式半椅式123456123456Potential energy of the conformatio

20、ns 各种构象势能关系图各种构象势能关系图46kJ/molPotential energy process 椅式构象之间的转变：46kJ/molPotential energyReaction process4.2.4.2 mono substituted cyclohexane CH3HCH3H250pmr.t.5 95 Reason 1: Van de waals forcesAtomHCH2CH3NPOR/pm120200200150190140AtomSFClBrIR/pm185135180195215CH3HCH3H250pmr.t.1,3二直立键二直立键相互作用相互作用6116Re

21、ason 2: Torsional strain162HHCCH3CH5a 键162CHHCCH3H5CH3HCH3He 键6161结论与推论：结论与推论：1、一取代时，取代基趋向于处于、一取代时，取代基趋向于处于e键键2、若有多个取代基，在满足顺反构型关系的前提下，、若有多个取代基，在满足顺反构型关系的前提下，则越多取代基处于则越多取代基处于e键时越稳定。键时越稳定。3、若环上有不同取代基，在满足顺反构型关系的前提、若环上有不同取代基，在满足顺反构型关系的前提下，则大基团处于下，则大基团处于e键时较稳定。键时较稳定。4.2.4.3 double substituted cyclohexane

22、 (same groups)a 键键e 键键a键、键、e键的顺反关系键的顺反关系Cis-1,2trans-1,2trans-1,31,1cis-1,3cis-1,4trans-1,44.2.4.4 double substituted cyclohexane (different groups)u Conformation with all groups on e bond is most preferred; 在满足空间构型的前提下，令尽可能多的取代基处于在满足空间构型的前提下，令尽可能多的取代基处于e键。键。u If the above condition can not be met,

23、the group with a bigger size is on the e bond. 优先满足大基团处于优先满足大基团处于e键。键。-F, -CN -Cl, -Br, -I -OCH3 -OH -COOH -NH2 -CH3 -CH2CH3 -CH(CH3)2 -C6H5 -C(CH3)3 注：注：1、OH，NH2易受溶剂的影响，尤其是形成氢键时。易受溶剂的影响，尤其是形成氢键时。 2、此顺序应用于、此顺序应用于1,2取代时可能有误差。取代时可能有误差。练习：画出以下结构的最稳定构象练习：画出以下结构的最稳定构象ButCH3ButH3CButCH3ButCH3ButCH3ButCH3B

24、utH3C4.2.5 Configuration of decalin 十氢合萘的构型十氢合萘的构型HHHH8.7kJ/mol more stable4.3 Physical properties & spectrum data物理性质： 环烷烃分子较规则，不易自由摇动 分子排列紧密 熔点、沸点、密度等一般高于相应的直链烷烃HHa-He-HTheoretically, e-H is 0.20.5 ppm larger than a-H . But due to the fast transform of cyclohexane, this difference is often invisible.1H-NMR环烷烃中环烷烃中CH2的的CH伸缩振动受环张力的影响，波数伸缩振动受环张力的影响，波数升高，强度下降。升高，强度下降。五元以下小环的亚甲基伸缩振动波数均大于五元以下小环的亚甲基伸缩振动波数均大于3000cm-1，大于，大于五元的环则与直链烷烃一样。五元的环则与直链烷烃一样。 4.4.1 Radical su