第2章：碳氢化合物课件.ppt

1、第二周预习思考题n1、有机化合物命名的一般步骤怎样？母体如何选择？各种基团（官能团）的英文词头或词尾的变化规律如何？n2、各种碳氢化合物的稳定性如何？芳香性与共振论是怎么回事？如何画极限共振结构式，并判断它们的能量高低？n3、化合物结构与物理性质的关系如何？n4、非共价弱作用力有哪些？第二章第二章碳氢化合物碳氢化合物Hydrocarbon第二章重点讲解问题n1.碳氢化合物的命名（以烷烃和环烷烃为例）n2.碳氢化合物的稳定性n3.共轭烯烃、芳香性与共振论和分子轨道理论n4.碳氢化合物的物理性质与分子间作用力关系2.1 碳氢化合物的分类与命名n2.1.1 Classification of hyd

2、rocarbonnAlkanes and CycloalkanesnAlkenes(cis and trans)(Z and E)nConjugated dienesnAromatic hydrocarbonsnAlkynes 2.1 碳氢化合物的分类与命名n2.1.2 Representing MoleculesnMolecular formula CH4 Hna Stick figure H C H na Lewis dot structure H na Sawhorse representation HCHHHCHHHH:a solid wedge-in front of the pla

3、nea hatched line-behind the plane2.1 碳氢化合物的分类与命名n2.1.3 通式与不饱和度（环的数目）n Saturated Hydrocarbons:CnH2n+2 n For a formula:CnHm n Degree of unsaturated=(2n+2-m)/2n n If it is a cycloalkane,the degree of unsaturated equals to the number of ring2.1.4 NomenclaturenCommon Name and Systematic Namen CH4 CH3CH3

4、CH3CH2CH3nMethane Ethane Propanen CH3CH2CH2CH3 CH3CHCH3n CH3 nC.N.n-butane isobutanenS.N.Butane 2-methylpropane2.1.4 NomenclaturenCH3CH2CH2CH2CH3 PentanenCH3CHCH2CH3 isopentane,2-methylbutanen CH3n CH3n CH3CCH3 neopentane,2,2-dimethylpropanen CH32.1.4 NomenclaturenCH3CH2CH2CH2CH2CH3 hexanenCH3CHCH2C

5、H2CH3 isohexane,2-methylpentanen CH3 n CH3n CH3CCH2 CH3 neohexane,2,2-dimethylbutanen CH3 2.1.4 NomenclaturenCH3CH2CHCH2CH3 none 3-methylpentane n CH3 nCH3CH-CHCH3 none 2,3-dimethylbutane n CH3 CH3 nAlkyl Group R-(replacing“ane”with“yl”)nprimary,secondary,tertiary,quaternary C,but only primary,secon

6、dary,tertiary H n(see our text)2.1.4 Nomenclature(IUPAC Rules)nSystematic Name(IUPAC Rules)n(IUPAC:International Union of Pure and Applied Chemistry)n1.Determine the number of carbon in the longest continuous carbon chain-This chain is called the parent hydrocarbon.n1 2 3 4 5 6 7 8nCH3CH2CHCH2CH2CH2

7、CH2CH3 3-methyl Octanen CH3 nCH3CHCH2CH2CH3 4-methyl Octanen CH2CH2CH2CH32.1.4 Nomenclature(IUPAC Rules)n2.Number the chain so that the substituent gets the lowest possible number.nCH3CH2CHCH2CHCH2CH2CH3 5-ethyl-3-methyloctanen CH3 CH2CH3 not 4-ethyl-6-methyloctanen because 3 4n CH2CH3nCH3CHCHCH2CH2

8、CHCH3 3-ethyl-2,6-dimethylheptanen CH3 CH3 not 5-ethyl-2,6-dimethylheptanen because 3 52.1.4 Nomenclature(IUPAC Rules)n3.Cite the name of the alkyl substituent before the parent hydrocarbon.-A number and a word are separated by a hyphen;numbers are separated by a comma.di,tri,tetra is used to expres

9、s the number of the same substituentsnCH3CH2CHCH2CHCH3 2,4-dimethylhexanen CH3 CH3 2.1.4 Nomenclature(IUPAC Rules)nAnd list substituents in alphabetical order.-“di,tri,tetra,sec,and tert”are ignored in alphabetizing.“iso,neo,and cyclo”are not ignored in alphabetizing.n 3HC2HC CH3nCH3CH2CCH2CH2CHCHCH

10、2CH2CH3 3,3,6-triethyl-7-methyldecanen 3HC2HC CH2CH3 n CH3nCH3CH2CH2CHCH2CH2CHCH3 5-isopropyl-2-methyloctanen CH(CH3)22.1.4 Nomenclature(IUPAC Rules)n4.If the same substituent number are obtained in both directions,the first cited group received the lower number.n CH3 3-ethyl-5-methylheptanenCH3CH2C

11、HCH2CHCH2CH3 notn CH2CH3 5-ethyl-3-methylheptanen Cl 2-bromo-3-chlorobutanenCH3CHCHCH3 notn Br 3-bromo-2-chlorobutane2.1.4 Nomenclature(IUPAC Rules)n5.If a compound had two or more chains of the same length,the parent hydrocarbon is the chain with the greatest number of substituents.nCH3CH2CHCH2CH2C

12、H3 CH3CH2CHCH2CH2CH3n CHCH3 CHCH3n CH3 CH3 n3-ethyl-2-methylhexane not 3-isopropylhexanen (two substituents)(one substituent)2.1.4 Nomenclature(IUPAC Rules)n6.If there are some complex substituents,we can use the similar method to name the substituents.nCH3CH2CHCH2CH2CH3 CH3CH2CH2CHCH2CH2CH3 n 1 2 1

13、 2 3n CHCH3 CH2CHCH3n CH3 CH3 n 3-isopropylhexane or 4-isobutylheptane orn3-(1-methylethyl)hexane 4-(2-methylpropyl)heptane2.1.4 Nomenclature(IUPAC Rules)n当一个饱和支链无环烃具有相同长度的链可作为当一个饱和支链无环烃具有相同长度的链可作为主链时，则选择的顺序为：主链时，则选择的顺序为：n1）具有侧链数目最多的链）具有侧链数目最多的链n 4-propyl-2,3,5-n trimethylheptanen notn 3-methyl-4-(1

14、,2-n dimethylpropyl)heptaneCH3CH2CHCHCHCH3CH2CH3CHCH3CH3CH2CH32.1.4 Nomenclature(IUPAC Rules)n2）侧链具有最低位次的链）侧链具有最低位次的链n2,5-dimethyl-4-(1-methylpropayl)heptane (not 3,4,5)CH CH2-CHCH3CHCH3CH3CH2CHCH2CH3CH3CH32.1.4 Nomenclature(IUPAC Rules)n3）在较短的侧链中，具有碳原子数目最多的链）在较短的侧链中，具有碳原子数目最多的链n（各侧链数分别为（各侧链数分别为1112

15、88和和111189）n3-ethyl-5,9,11-trimethyl-7,7-di(2,4-dimethylhexyl)tridecaneCCH2CHCH2CHCH2CH3CH2CHCH2CHCH2CH3CH3CH2CHCH2CHCH2CH3CH2CHCH2CHCH2CH3CH3CH3CH3CH3CH2CH3CH3CH3课堂练习：n请给出上述结构的中英文IUPAC命名n1、4-(1-ethylpropyl)-2,5,6,6-tetramethyloctanen2、1-ethyl-2-mehylcyclopentaneCH3CH2C-CHCHCH2CHCH3CH3CHCH2CH3CH3CH3

16、CH2CH3CH3CH2CH3CH31、2、2.1.4 Nomenclature(IUPAC Rules)n7.For cycloalkane:(skeletal structure)n1)In the case of a cycloalkane with an attached alkyl substituent,the ring is the parent hydrcarbon unless the substituent has more carbons than the ring.nA.IsopropylcyclohexanenB.1-cyclobutylpentaneCH2(CH3)

17、2CH2CH2CH2CH2CH3A.B.2.1.4 Nomenclature(IUPAC Rules)n2)If the ring has two different substituents,they are cited in alphabetical order and the number 1 position is given to the first cited substituent.nA.1-ethyl-3-methylcyclopentanenB.1,3-dimethylcyclohexane CH2CH3H3CCH3H3CA.B.2.1.4 Nomenclature(IUPA

18、C Rules)n3)If there are more than two substituents on the ring,give the number 1 position to the substituent that result in a second substituent getting as low a number as possible.nA.1,1,2-trimethylcyclopentane (not 1,2,2;not 1,1,5)nB.4-ethyl-2-methyl-1-propylcyclohexane not 1,3,4,(23);not 5,1,2,(4

19、5)CH3CH3CH3H3CH2CH2CH3CCH2CH3A.B.n以下内容请自学：nNomenclature of Alkenes(cis and trans)n (Z and E)n Alkynesn Conjugated dienesn Aromatic hydrocarbons2.2 碳氢化合物的稳定性碳氢化合物的稳定性n2.2.1 Saturated hydrocarbons-Alkanesn relatively stablen2.2.2 Cycloalkanes-Ring Strainn Instability of three-and four-member rings n -

20、due to angle strain109.506009002.2 碳氢化合物的稳定性碳氢化合物的稳定性n2.2.3 Alkenes-Pi BondingnThe functional group is the center of reactivity of a molecule.Carbon-carbon double bond(C=C)is the functional group of alkenes.nStrength of Bond:C-C 347.3 kJ/molen C=C 610.9 kJ.molena Pi Bond is weaker than a Sigma Bond

21、2.2 碳氢化合物的稳定性碳氢化合物的稳定性n2.2.4 Alkynes-Pi BondnStrength of Bond:C-C 347.3 kJ/molen C=C 610.9 kJ.molen C=C 836.8 kJ/molenPi Bond in C=C:263.6 kJ/molenPi Bond in C=C:244.8 kJ/molenan alkyne is less reactive than an alkenenWhy?（Please think it out by yourself）2.2 碳氢化合物的稳定性碳氢化合物的稳定性nClass of dienes:conjug

22、atedn isolatedn cumulatednHeat of Formation:n n C +n H2 CnH2n +heat(Hf0 )GraphiteGas2.2 碳氢化合物的稳定性碳氢化合物的稳定性nThe difference between the heats reflects the difference in stability between the nonconjugated and conjugated dienesC-70.5 kcal/mole-60.8 kcal/mole-54.1 kcal/mole+2H2+2H2+2H22.2 碳氢化合物的稳定性碳氢化合物

23、的稳定性n2.2.5 Aromatic hydrocarbonsnBenzene,with relatively few hydrogens comparing with aliphatic compound,is a particularly stable compound because it has an unusually large resonance energy 151kJ/mole)3 H2H0-49.3 kcal/moleH0-28.4 kcal/moleH2nQuestions:nWhy is a conjugated diene more stable than an i

24、solated diene?nWhy is benzene a particularly stable compound?2.3 共轭烯烃、芳香性与共振论和分子轨道理论nConjugated Dienesn1.Single bond between C2-C3 formed by sp2-sp2 overlap,the length of the bond is shorter,therefore the bond is stronger.nCH3-CH3 Csp3-Csp3 154pmnCH2=CH-CH3 Csp2-Csp3 150pmnCH2=CH-CH=CH2 Csp2-Csp2 14

25、6pm2.3 共轭烯烃、芳香性与共振论和分子轨道理论n2.Structure of Conjugated Dienes:n3.The conjugated diene had delocalized electrons.We can draw the resonance structure:nresonance hybrid:H2CCHCHCH2CH2-CH=CH-CH2 CH2=CH-CH=CH2 CH2-CH=CH-CH2+-2.3 共轭烯烃、芳香性与共振论和分子轨道理论n分子轨道理论阐述1，3-丁二烯的结构2.3 共轭烯烃、芳香性与共振论和分子轨道理论nStructure of Benz

26、enen1.All the carbon are sp2 hybridizedn2.The p orbital on each carbon can overlap with two adjacent p orbitals.n3.p-electrons in benzene are delocalized,we call such compound to have resonance.2.3 共轭烯烃、芳香性与共振论和分子轨道理论n电子离域与共振n上述结构较好地表示了电子的离域，但是却无法告诉我们该结构中含有多少双键。因此化学家常用共振结构来表示。2.3 共轭烯烃、芳香性与共振论和分子轨道理论

27、nSome basic conceptsn1.A compound with delocalized electrons is said to have resonancen2.The approximate structure using localized electrons is called a resonance contributor,a resonance structure,or a contributing resonance structuren3.The catual structure,drawn using delocalized eletrons,is called

28、 a resonance hybrid.2.3 共轭烯烃、芳香性与共振论和分子轨道理论nRules for Drawing Resonance Contributorsn1.Only electrons move.The nuclei of the atoms never moven2.The only electrons that can move are electrons and nonbonding electronsn3.The total number of electrons in the molecule does not change,neither do the numbe

29、rs of paired and unpaired electrons2.3 共轭烯烃、芳香性与共振论和分子轨道理论n4.The electrons can be moved in one of the following waysn1)Move electrons toward a positive charge or toward a bondH3CHCCHCHCH3CH3CH=CH-CHCH3 CH3CH-CH=CHCH3+2.3 共轭烯烃、芳香性与共振论和分子轨道理论n2)Move a nonbonding pair of electrons toward a bondCH3CH=CH

30、-O-CH3 CH 3 CH-CH=O-CH3H3CHCCHOCH3resonance contributorsresonance hybrid2.3 共轭烯烃、芳香性与共振论和分子轨道理论n3.Move a single nonbonding electron toward a bondH3CCHCHCH2H3CCHCHCH2H3CCHCHCH2resonance contributorsresonance hybrid课堂练习：n请给出上述结构的中英文IUPAC命名n1、4-(1-ethylpropyl)-2,5,6,6-tetramethyloctane not 3,3,4,7-tetr

31、amethyl-5-(1-ethylpropyl)-n2、1-ethyl-2-mehylcyclopentaneCH3CH2C-CHCHCH2CHCH3CH3CHCH2CH3CH3CH3CH2CH3CH3CH2CH3CH31、2、2.3 共轭烯烃、芳香性与共振论和分子轨道理论n2.Structure of Conjugated Dienes:n3.The conjugated diene had delocalized electrons.We can draw the resonance structure:nresonance hybrid:H2CCHCHCH2CH2-CH=CH-CH2

32、CH2=CH-CH=CH2 CH2-CH=CH-CH2+-2.3 共轭烯烃、芳香性与共振论和分子轨道理论nAromaticity and Huckels RulenBenzene-perticularly stable because of the resonance energynBut cyclobutadiene and cyclooctatetraene containscyclic two or four Pi-bond,they are not stable.Aromaticity and Huchels RulenIn 1938,a German chemist Erich Hu

33、ckel recognized the difference between them and generalized this obeservation into Huckels Rulen-any plannar,cyclic,conjugated system containing(4n+2)Pi electrons(where n is an integer)experiences unusual aromatic stabilizationAromaticity and Huchels RulenMolecular Orbital theoryn-in benzene6Aromati

34、city and Huchels RulenMolecular Orbital theory n-in cyclooctatetraene8Aromaticity and Huchels RulenOther member rings0-1-2120.618-1.6181.247-.445-1.8021.414-1.414Aromaticity and Huchels RulenOther Aromatic molecules:n1，6-桥连桥连10-轮烯轮烯n14-轮烯，轮烯，18-轮烯，轮烯，22-轮烯轮烯n（请思考为什么（请思考为什么10-轮烯没有芳香性）轮烯没有芳香性）+-+2.4 碳

35、氢化合物的物理性质碳氢化合物的物理性质n2.4.1.Boiling PointsnDepend on the strength of the attractive forces between the individual moleculesnIn Alkanes:C-C C-H nonpolar bondsnvan der Waals forces-induced dipole-induced-dipole interactions nC=O,C-O polar bondsndipole-dipole interaction2.4 碳氢化合物的物理性质碳氢化合物的物理性质nVan der W

36、aals forces are the weakest of all the intermolecular attractionnIt depends on the area of contact between the moleculesnThe boiling points of alkanes increase as their size increasenAnd a branched compound has a relatively lower boiling point2.4 碳氢化合物的物理性质碳氢化合物的物理性质n2.4.2.Melting PointsnPacking inf

37、luences the melting point of a compoundnPacking is a property that determines how well the individual molecules in a sold fit together in the crystal latticenThe tighter the fit,the more energy required to break the lattice and melt the compound.2.4 碳氢化合物的物理性质碳氢化合物的物理性质n2.4.3 SolubilitynGeneral Rule:Like dissolves like第二章重点讲解问题n1.碳氢化合物的命名（以烷烃和环烷烃为例）n2.碳氢化合物的稳定性n3.共轭烯烃、芳香性与共振论和分子轨道理论n4.碳氢化合物的物理性质与分子间作用力关系