1、Cycloalkanes第四章第四章 環烷烴環烷烴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, Isomeriz

2、ation and nomenclature 4.1.1 Classification 4.1.2 Isomerism 4.1.3 Nomenclature4.1.1 ClassificationBy the size of the ring 按環的大小按環的大小Small ringsMedium ringsCommon ringsLarge ringsC3C4C8C12C5C7C13By the saturation 按不飽和度按不飽和度CnH2nCnH2n-2CnH2n-4Cycloalkanes 環烷環烷Cyclo olefines 環烯環烯Cyclo alkynes 環炔環炔Monoc

3、yclic compounds 單環單環By the number of the rings 按環的數目按環的數目Polyring compounds 多環多環Fused ring 稠環稠環Bridged ring 橋環橋環Spiro rings 螺環螺環兩環之間共用一個兩環之間共用一個碳原子碳原子兩環之間共用一根共兩環之間共用一根共價鍵（共用兩個直接價鍵（共用兩個直接相連的碳原子）相連的碳原子）兩環之間共用兩個兩環之間共用兩個不直接相連的碳原不直接相連的碳原子子螺原子橋頭碳To define the number of the rings:The number of cutting you

4、need to get a chain molecule out of a poly ring compound幾環？將橋（稠）環烴變為鏈狀化合物時需要斷裂的碳鏈將橋（稠）環烴變為鏈狀化合物時需要斷裂的碳鏈數。如需斷裂兩次，則為二環化合物，斷裂三次則數。如需斷裂兩次，則為二環化合物，斷裂三次則為三環化合物。為三環化合物。Some interesting bridging compoundsCubane立方烷立方烷Primane棱棱 烷烷Diamentane金剛烷金剛烷籃籃 烷烷4.1.2 Isomerism Constitutional isomers are derivated from t

5、he change of size of rings and length of side chainsC5H10環的大小及側鏈長短與位置變化環的大小及側鏈長短與位置變化4.1.3 Nomenclature 命名命名4.1.3.1 Monocyclic alkane 單環烷烴單環烷烴1, When the side chain is not very complicate: 當支鏈不復雜時，以環烷烴為母體當支鏈不復雜時，以環烷烴為母體methylcyclopentane2-ethyl-4-methyl-1-propylcycloheptane1-ethyl-3-methylcyclopenta

6、ne1,2-dimethylcyclopentane1,2-二甲基環戊烷二甲基環戊烷甲基環戊烷甲基環戊烷1-甲基甲基-3-乙基乙基環戊烷環戊烷4-甲基甲基-3-乙基乙基-1-丙基環己烷丙基環己烷2, When the side chain is complicate or difficult to name: 當支鏈較復雜或不易命名時，以環烷基為取代基當支鏈較復雜或不易命名時，以環烷基為取代基3-cyclohexylhexane3-環己基己烷環己基己烷3, When two rings are connected 兩環相連時兩環相連時Cyclopropylcyclohexane環丙基環己烷環丙

7、基環己烷Cyclopropylcyclopropane環丙基環丙烷環丙基環丙烷4, Cis and trans isomerism:CH3CH3HHCH3HCH3HCH3CH3CH3CH3Cis-1,4-dimethylcyclohexaneTrans-1,4-dimethylcyclohexaneHow to name this compound ?CH3CH3CH34.1.3.2 Polyring alkane 多環烷烴多環烷烴1, Spiro cycloalkanes 螺環烴螺環烴123456789101“小原則”：在不違背螺環烴命名的“大”原則基礎上，在編號時應盡可能令取代基的位號最小

8、。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 橋環烴和稠環烴橋環烴和稠環烴12345678bicyclo3.2.1octane二環二環3.2.1辛烷辛烷2,7,7-trimethylbicyclo2.2.1heptanebicyclo1.1

9、.0butane2,7,7-三甲基二環三甲基二環2.2.1庚烷庚烷注意：有兩個橋頭碳可注意：有兩個橋頭碳可供選擇供選擇二環二環1.2.0丁烷丁烷For polycyclic compound as following 多元環多元環Deciding the main ring 選選“主環主環”：最大的環：最大的環Choosing the main bridged carbon 選選“主橋頭碳主橋頭碳”：主環與非主環的最長橋共用的橋頭碳：主環與非主環的最長橋共用的橋頭碳Decide the serial number 編號：從主橋頭碳開始；從最長橋開始編號：從主橋頭碳開始；從最長橋開始Naming

10、 the compound 書寫（注意與非主橋相連的橋需注明所連橋的編號）書寫（注意與非主橋相連的橋需注明所連橋的編號）1234567Tricyclic2.2.1.02.6heptane思考：12345678910Tricyclic3.2.2.12.7decanetricyclic3.2.2.12.7dacaneFused ringnaphthaleneHydrogenated naphthaleneEndo/exaOHHendoHOHexa區別：母體！區別：母體！ 4.2.1 Baeyers strain theory 4.2.2 Heat of combustion for cycloal

11、kane 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 hexa rings do not exist, or are not stable.W.H.Perk

12、in 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張力學說張力學說Assumption:1, carbon atoms in the ring are on the same plane; 成環的碳原子均在同一同面上，且呈正多邊

13、形成環的碳原子均在同一同面上，且呈正多邊形2, carbon atoms are sp3 carbon atoms; 碳原子采取碳原子采取sp3雜化形式，正常鍵角應為約雜化形式，正常鍵角應為約109.5度度3, to meet some special angles in the ring, the bonds have to be bending; 為了滿足平面正多邊形的內角要求，成環的鍵必須向內或向外為了滿足平面正多邊形的內角要求，成環的鍵必須向內或向外“屈撓屈撓”， “ “屈撓屈撓”的程度越大，體系越不穩定。的程度越大，體系越不穩定。More bendingMore angle stra

14、inHigher energyLess stability60o90o108o120o129oMost stable?可解釋一些體系的穩定性特點，但還有一些體系無法解釋。 4.2.2 Heat of combustion for cycloalkane Heat of combustion per CH2kJ/mol697686664659662n658Do not fit the strain theory!p 角張力（Baeyer 張力）p 扭轉張力p 范氏力影響環體系穩定性的主要因素： 4.2.3 Current opinionsCCC105.5oCCCBent Bond （彎曲鍵、香蕉

15、鍵）（彎曲鍵、香蕉鍵）角張力：角張力：109.50-105.50=4012HHHH12CH233扭轉張力：扭轉張力：三組三組HCC均處于全重疊式均處于全重疊式HHHHHHHHHHHHHHHHA nonplanar conformation 非平面構象非平面構象 也存在彎曲鍵也存在彎曲鍵 111.50角張力：角張力：111.50109.50 = 20123HHH2CH2CHH4部分交叉式部分交叉式扭轉張力較小扭轉張力較小6.3kJ/mol higher全重疊式全重疊式2.5kJ/molenvelop structurehalf-chair structure信封式 半椅式具有多組全重疊式具有多組

16、全重疊式Large ring多于多于13個碳原子的環體系中，分子鏈一般呈皺折形個碳原子的環體系中，分子鏈一般呈皺折形Strain energy in cycloalkanesNameAngle strainTwist strainVan de waalsC3GreatMediumNoC4GreatMediumNoC5SlightMediumNoC6NoNoNoC7C12MediumMediumGreatC12NoNoNo4.2.4 Conformations of cyclohexaneYearName of scientistPoint of view1883BaeyerAssumes th

17、at 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)1950D.BartonConformation analysis of cyclohexaneA his

18、tory4.2.4.1 Conformation of cyclohexane250pmC350pmChair Structure 椅式椅式123456123HHH2CCH2HH465HHHH部分交叉式，扭轉張力較小部分交叉式，扭轉張力較小Axial bondEquatorial bondTwo types of C-H bonds in chair structurea 鍵鍵e 鍵鍵Boat structure 船式結構船式結構183pmVan de waal radius of H atom is 120pm, so the two adjacent hydrogen atoms caus

19、es serious excluding.存在范氏力存在范氏力123456HHHH651HH2CHHHH2C423全重疊式，存在扭轉張力全重疊式，存在扭轉張力2、3、5、6碳處于同一平面碳處于同一平面Flagpole interactionTwist boat structure 扭船式扭船式HHHHHHHHHHHH123456123456123456Half chair structure 半椅式半椅式123456123456Potential energy of the conformations 各種構象勢能關系圖各種構象勢能關系圖46kJ/molPotential energy pro

20、cess 椅式構象之間的轉變：46kJ/molPotential energyReaction process4.2.4.2 mono substituted cyclohexane CH3HCH3H250pmr.t.5 95 Reason 1: Van de waals forcesAtomHCH2CH3NPOR/pm120200200150190140AtomSFClBrIR/pm185135180195215CH3HCH3H250pmr.t.1,3二直立鍵二直立鍵相互作用相互作用6116Reason 2: Torsional strain162HHCCH3CH5a 鍵162CHHCCH3

21、H5CH3HCH3He 鍵6161結論與推論：結論與推論：1、一取代時，取代基趨向于處于、一取代時，取代基趨向于處于e鍵鍵2、若有多個取代基，在滿足順反構型關系的前提下，、若有多個取代基，在滿足順反構型關系的前提下，則越多取代基處于則越多取代基處于e鍵時越穩定。鍵時越穩定。3、若環上有不同取代基，在滿足順反構型關系的前提、若環上有不同取代基，在滿足順反構型關系的前提下，則大基團處于下，則大基團處于e鍵時較穩定。鍵時較穩定。4.2.4.3 double substituted cyclohexane (same groups)a 鍵鍵e 鍵鍵a鍵、鍵、e鍵的順反關系鍵的順反關系Cis-1,2tr

22、ans-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; 在滿足空間構型的前提下，令盡可能多的取代基處于在滿足空間構型的前提下，令盡可能多的取代基處于e鍵。鍵。u If the above condition can not be met, the group with a bigger size is on the e bond. 優先

23、滿足大基團處于優先滿足大基團處于e鍵。鍵。-F, -CN -Cl, -Br, -I -OCH3 -OH -COOH -NH2 -CH3 -CH2CH3 -CH(CH3)2 -C6H5 -C(CH3)3 注：注：1、OH，NH2易受溶劑的影響，尤其是形成氫鍵時。易受溶劑的影響，尤其是形成氫鍵時。 2、此順序應用于、此順序應用于1,2取代時可能有誤差。取代時可能有誤差。練習：畫出以下結構的最穩定構象練習：畫出以下結構的最穩定構象ButCH3ButH3CButCH3ButCH3ButCH3ButCH3ButH3C4.2.5 Configuration of decalin 十氫合萘的構型十氫合萘的構

24、型HHHH8.7kJ/mol more stable4.3 Physical properties & spectrum data物理性質： 環烷烴分子較規則，不易自由搖動 分子排列緊密 熔點、沸點、密度等一般高于相應的直鏈烷烴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環烷烴中環烷烴中CH2的的CH伸縮振動受環張力的影響，波數伸縮振動受環張力的影響，波數升高，強度下降。升高，強度下降。五元以下小環的亞甲基伸縮振動波數均大于五元以下小環的亞甲基伸縮振動波數均大于3000cm-1，大，大于五元的環則與直鏈烷烴一樣。于五元的環