有機(jī)化學(xué)課件清華梅chapter4cycloalkanes環(huán)烷烴

1、Cycloalkanes第四章環(huán)烷烴Organic Chemistry A (1)By Prof. Li Yan-Mei Tsinghua UniversityContent4.14.24.34.44.5Classification, Isomerization and nomenclatureStructure of cycloalkanesPhysical properties & spectrum data Chemical propertiesPreparation (learn on your own)4.1 Classification, Isomerization and

2、 nomenclature4.1.1Classification4.1.2Isomerism4.1.3Nomenclature4.1.1ClassificationBy the size of the ring按環(huán)的大小Small ringsC3C4Common ringsC5C7Large ringsMedium ringsC8C12C13By the saturation按不飽和度CnH2n CnH2n-2CnH2n-4Cycloalkanes環(huán)烷Cyclo olefines環(huán)烯Cyclo alkynes環(huán)炔By the number of the rings按環(huán)的數(shù)目Monocyclic

3、 compounds單環(huán)橋頭碳Polyring compounds多環(huán)螺原子Spiro rings螺環(huán)Bridged ring橋環(huán)Fused ring稠環(huán)兩環(huán)之間共用一個(gè)碳原子兩環(huán)之間共用一根共價(jià)鍵（共用兩個(gè)直接相連的碳原子）兩環(huán)之間共用兩個(gè)不直接相連的碳原子幾環(huán)？To define the number of the rings:The number of cutting you need to get a chain molecule out of a poly ring compound將橋（稠）環(huán)烴變?yōu)殒湢罨衔飼r(shí)需要斷裂的碳鏈數(shù)。如需斷裂兩次，則為二環(huán)化合物，斷裂三次則為三環(huán)化合物。

4、Some interesting bridging compoundsCubane立方烷Primane棱 烷Diamentane烷籃 烷4.1.2IsomerismConstitutional isomers are derivated from the change of size of rings and length of side chainsC5H10環(huán)的大小及側(cè)鏈長(zhǎng)短與位置變化4.1.3Nomenclature命名4.1.3.1Monocyclic alkane 單環(huán)烷烴1,When the side chain is not very complicate:當(dāng)支鏈不復(fù)雜時(shí)，以環(huán)烷

5、烴為母體methylcyclopentane甲基環(huán)戊烷1,2-dimethylcyclopentane1,2-二甲基環(huán)戊烷2-ethyl-4-methyl-1- propylcycloheptane4-甲基-3-乙基-1-丙基環(huán)己烷1-ethyl-3-methylcyclopentane1-甲基-3-乙基環(huán)戊烷2,When the side chain is complicate or difficult to name:當(dāng)支鏈較復(fù)雜或不易命名時(shí)，以環(huán)烷基為取代基3-cyclohexylhexane3-環(huán)己基己烷3,When two rings are connected兩環(huán)相連時(shí)Cyclop

6、ropylcyclohexane環(huán)丙基環(huán)己烷Cyclopropylcyclopropane環(huán)丙基環(huán)丙烷4, Cis and trans isomerism:CH3CH3CH3HHHHCH3CH3CH3CH3Cis-1,4-dimethylcyclohexaneCH3Trans-1,4-dimethylcyclohexaneCH3CH3CH3How to name this compound ?4.1.3.2 Polyring alkane1, Spiro cycloalkanes多環(huán)烷烴螺環(huán)烴1）選母體：根據(jù)的總碳原子數(shù)，稱為“螺某烷”。2） 編號(hào)：從小環(huán)開始；從第一個(gè)3） 書寫：先寫詞頭“螺

7、”方括號(hào)內(nèi)沿著編號(hào)方向?qū)懗雒總€(gè)環(huán)中除螺原子原子開始。167外的每個(gè)環(huán)的碳原子數(shù)1239104螺4.5癸烷5數(shù)字之間用圓點(diǎn)隔開8最后寫出螺原子在內(nèi)碳原子數(shù)的烷烴名稱“小原則”：在不違背螺環(huán)烴命名的“大”原則基礎(chǔ)上，在編號(hào)時(shí)應(yīng)盡可能令取代基的位號(hào)最小。167235849101-甲基螺4.5癸烷思考！67128534910spiro5.5undecane螺5.5十一烷spiro4.5decane螺4.5癸烷2-methylspiro4.5decane6-甲基4.5癸烷4-methylspiro2.4heptane4-甲基2.4庚烷2, Bridged-ring alkane and fused-ri

8、ng alkane橋環(huán)烴和稠環(huán)烴1）選母體：根據(jù)的總碳原子數(shù)及環(huán)數(shù)，稱為“n環(huán)某烷”。2） 編號(hào)：從橋頭碳開始；從最長(zhǎng)橋開始。3） 書寫：先寫環(huán)數(shù)方括號(hào)內(nèi)沿著編號(hào)方向?qū)懗雒總€(gè)環(huán)中除橋頭碳原子外的每個(gè)環(huán)的碳原子數(shù)數(shù)字之間用圓點(diǎn)隔開8132最后寫出橋頭碳原子在內(nèi)碳原子數(shù)的烷烴名稱7645bicyclo3.2.1octane二環(huán)3.2.1辛烷注意：有兩個(gè)橋頭碳可供選擇2,7,7-trimethylbicyclo2.2.1heptane2,7,7-三甲基二環(huán)2.2.1庚烷bicyclo1.1.0butane二環(huán)1.2.0丁烷For polycyclic compound as following多元環(huán)

9、Deciding the main ring選“主環(huán)”：最大的環(huán)Choosing the main bridged carbon選“主橋頭碳”：主環(huán)與非主環(huán)的最長(zhǎng)橋共用的橋頭碳Decide the serial number編號(hào)：從主橋頭碳開始；從最長(zhǎng)橋開始7Nathe compound書寫（注意與非主橋相連的橋需注明所連橋的編號(hào)）453126Tricyclic2.2.1.02.6heptane思考：12897310564tricyclic3.2.2.12.7dacaneTricyclic3.2.2.12.7decaneFused ring區(qū)別：母體！naphthaleneHydrogenat

10、ed naphthaleneEndo/exaOHHHOHexaendo4.2Structure of cycloalkanes4.2.14.2.24.2.34.2.44.2.5Baeyers strain theoryHeat of combustion for cycloalkane Current opinionsConformations of cyclohexaneConfiguration of decalinBefore 1880Only penta rings and hexa rings were found. It was regarded that rings smalle

11、r than penta rings and bigger than hexa rings do not exist, or are not stable.1883W.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 theory4.2.1Baeyers strain theo

12、ryBayers張力學(xué)說Assumption:1, carbon atoms in the ring are on the same plane;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sp3雜化形式，正常鍵角應(yīng)為約109.5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(nèi)角要求，“屈撓”， “屈撓”的程度越大，體系越不的鍵必須向內(nèi)或。More bendingMore angle strain

13、Higher energyLess stability60o90o108o120o129oMoststable?可解釋一些體系的性特點(diǎn)，但還有一些體系無法解釋。4.2.2Heat of combustion for cycloalkanenHeat of combustion per CH2 kJ/mol697686664659662658Do not fit the strain theory!影響環(huán)體系性的主要因素：角張力（Baeyer 張力）扭轉(zhuǎn)張力范氏力ppp4.2.3Current opinions3CH2H H扭轉(zhuǎn)張力：三組HCC 均處于全重疊式21231H HCC角張力：109.

14、50-105.50=40CCCC105.5oBent Bond （彎曲鍵、香蕉鍵）A nonplanar conformation非平面構(gòu)象111.50也彎曲鍵角張力：111.50109.50 = 20部分交叉式HHHH扭轉(zhuǎn)張力較小H4HH3 HH2HHHH4H2C1HHHHH蝴蝶狀蝴蝶式1H2H C23H6.3kJ/mol higher全重疊式2.5kJ/molenvelop structualf-chair structure信封式半椅式如果：具有多組全重疊式Large ring多于13個(gè)碳原子的環(huán)體系中，分子鏈呈皺折形Strain energy in cycloalkanesNameAn

15、gle strainTwist strainVan de waalsC4GreatMediumNoC6NoNoNoC12NoNoNoC7C12MediumMediumGreatC5SlightMediumNoC3GreatMediumNo4.2.4Conformations of cyclohexaneA historyYearName of scientistPoint of view1883BaeyerAssumes that six carbon atoms are on the same plane1890H.SachseTwo conformations may exist1915-

16、1918W.M.MohrChair mand boat m1920Cyclohexane was proved to be nonplanar experimentally1943O.HasselChair mis most stable (electron diffraction method)1950D.BartonConformation analysis of cyclohexane4.2.4.1Conformation of cyclohexaneChair Structure椅式HH1 H2C250pmHH51662H53HC H243H42H部分交叉式，扭轉(zhuǎn)張力較小C350pma

17、 鍵Axial bonde 鍵Equatorial bondTwo types of C-H bonds in chair structureBoat structure 船式結(jié)構(gòu)H21 CH HHHH2 C46Flagpole interaction25183pm3HHH H14全重疊式，扭轉(zhuǎn)張力5623Van de waal radius of H atom is 120pm, so the two adjacent hydrogen atoms causes serious excluding.范氏力2、3、5、6碳處于同一平面Twist boat structure扭船式H1H4HH1

18、H H64415 25256H 23H6H33HHHHalf chair structure半椅式466545112323Potential energy of the conformations各種構(gòu)象勢(shì)能圖46kJ/molprocessPotential energy椅式構(gòu)象之間的轉(zhuǎn)變：46kJ/molReaction processPotential energy4.2.4.2mono substituted cyclohexane250pmHCH3Hr.t.CH35 95 Reason 1:Van de waals forces250pm1,3二直立鍵相互作用r.t.HCH316HCH

19、361AtomHCH2CH3NPOR/pm120200200150190140AtomSFClBrIR/pm185135180195215Reason 2:Torsional strainHCH316HCH361HH3C5C2CCH3H6165 CHH1C2a 鍵HHe 鍵結(jié)論與推論：1、一取代時(shí)，取代基趨向于處于e鍵2、若有多個(gè)取代基，在滿足順反構(gòu)型的前提下，則越多取代基處于e鍵時(shí)越。3、若環(huán)上有不同取代基，在滿足順反構(gòu)型的前提下，則大基團(tuán)處于e鍵時(shí)較。4.2.4.3double substituted cyclohexane (same groups)a鍵、e鍵的順反a 鍵e 鍵1,1Ci

20、s-1,2trans-1,2trans-1,3cis-1,3cis-1,4trans-1,44.2.4.4double substituted cyclohexane (different groups)uConformation with all groups on e bond is mostpreferred;盡可能多的取代基處于e鍵。在滿足空間構(gòu)型的前提uIf the above condition can not be met, the group with a bigger size is on the e bond.優(yōu)先滿足大基團(tuán)處于e鍵。-F, -CN < -Cl, -B

21、r, -I < -OCH3 < -OH < -COOH < -NH2 <-CH3 < -CH2CH3 < -CH(CH3)2 < -C6H5 < -C(CH3)3注：1、OH，NH2易受溶劑的影響，尤其是形成氫鍵時(shí)。2、此順序應(yīng)用于1,2取代時(shí)可能有誤差。練習(xí)：畫出以下結(jié)構(gòu)的最構(gòu)象ButButButCH3ButCH3CH3H3CButButButCH3H3CCH34.2.5Configuration of decalin十氫合萘的構(gòu)型HH8.7kJ/mol more stableHH4.3 Physical properties &

22、 spectrum data物理性質(zhì)：環(huán)烷烴分子較規(guī)則，不分子排列緊密熔點(diǎn)、沸點(diǎn)、密度等搖動(dòng)高于相應(yīng)的直鏈烷烴1H-NMRTheoretically, e-H is 0.20.5 ppm larger than a-H . But due to the fast transform of cyclohexane, this difference isoften invisible.He-HHa-Hdcyclopropane0.22dcyclobutane= 1.96dother= 1.513C-NMR345678910nd(ppm)-2.823.126.327.628.226.625.825.0IR環(huán)烷烴中CH2的CH伸縮振動(dòng)受環(huán)張力的影響，波數(shù)升高，強(qiáng)度下降。五元以下小環(huán)的亞甲基伸縮振動(dòng)波數(shù)均大于3000cm-1，大于五元的環(huán)則與直鏈烷烴一樣。4.4Chemical properties4.4.14.4.24.4.3Radical substitution reactionsCharacteristic reaction Oxidation4.4.1Radical substitution reaction