文本案例课件ch2upload-1alkanes

1、Chapter 2 Alkanes2013 Wei Dong Nanjing University of Science & Technology All Rights ReservedContents 烃的分类 烷烃的通式，同系列和构造异构 烷烃的命名 烷基的概念 （1）伯、仲、叔碳和伯、仲、叔氢 （2）烷基 烃的分类 烷烃 开链烃（脂肪烃） 烯烃 烃 炔烃 闭链烃 脂环烃 （环烃） 芳香烃 有机化学的基础是结构理论，进行上面分类的依据是它们的结构不同，今后我们按照这样的分类逐类进行学习。在学习每一类有机化合物时要搞清楚两方面内容： （1）一类化合物在结构与性质上有什么特征。 （2）这类化合

2、物中结构与性质是怎样变化的。 要求：不要仅仅记住这些事实，而是一有 可能便试图通过结构理解这些性质，并且 根据结构的差异来解释性质的差异。烷烃的通式和构造异构 碳原子数 结构式 分子式 名称 Name 1 CH4 CH4 甲烷 methane 2 CH3CH3 C2H6 乙烷 ethane 3 CH3CH2CH3 C3H8 丙烷 propane 4 CH3CH2CH2CH3 C4H10 丁烷 butane CH3 CH CH3 C4H10 异丁烷 isobutane CH3 经考察发现烷烃有如下三个规律： (1) 烷烃异构数目随碳原子数增加而增加。 (2) 烷烃分子的通式为CnH2n+2。 (

3、3) 相邻两个烷烃的分子式都相差一个CH2。烷基的概念 R，Radical；Residue 碳原子数 烷烃 烷基 名称 Name 缩写 1 CH4 CH3 甲基 methyl Me 2 CH3CH3 CH3CH2 乙基 ethyl Et 3 CH3CH2CH3 CH3CH2CH2 正丙基 n-propyl n-pr CH3CHCH3 异丙基 iso-propyl i-pr 碳原子数 烷烃 烷基 名称 Name 缩写 4 CH3CH2CH2CH3 CH3CH2CH2CH2 正丁基 n-butyl n-Bu CH3CHCH2 CH3 异丁基 iso-butyl i-Bu CH3 CH2 CH CH

4、3 CH3 CH2 CH 仲丁基 sec-butyl sec-Bu CH3 CH3 CH3 C 叔丁基 tert-butyl t-Bu CH3 tert: tertiary In branched alkanes, carbons are oftenclassified by their degree of branching.CH3CH3CH3CH3CH3CH3CH3CH3CH3CH2CH2CHCHCHCisopropylisobutylsec-butyltert-butylprimary (1): bonded to one other carbonsecondary (2): bonde

5、d to two other carbonstertiary (3): bondedto three other carbons 烷烃的命名 习惯命名法 衍生物命名法 IUPAC命名法 Nomenclature of simple alkanesAccording to IUPAC convention, the chemical name of analkane is based on the length of the parent chain. Thename is composed of a prefix to indicate the number ofcarbons in the

6、parent chain, followed by the suffix, ane toindicate the functional group is an alkane.Prefixmeth. eth. prop. but. pent. hex. hept.oct. non. dec. Number of Carbons 1 2 3 4 5 6 7 8 9 10IUPAC rules for the nomenclature ofsimple (unbranched) alkanesThe name is composed of a prefix to indicate thenumber

7、 of carbons in the parent chain, followed bythe suffix, ane to indicate the functional group is analkaneheptanepentanehexaneBranched alkanes also have widely usedcommon names.CH3CH3CH3CH3CH3CH3CH3CH3CH3CH2CH2CHCHCHCisopropylisobutylsec-butyltert-butylIUPAC rules for the systematicnomenclature of bra

8、nched alkanes1. For branched alkanes: the longest continuous chaindetermines the base name for the alkane.Indicate the longest continuous carbon chains inthe molecules shown above.IUPAC rules for the systematicnomenclature of branched alkanes1. For branched alkanes: the longest continuous chaindeter

9、mines the base name for the alkane.Indicate the longest continuous carbon chains inthe molecules shown above.2. Number the atoms in the chain, beginning at the endnearer the first substituent on the chain. If there aresubstituents occurring at equal distances from both endsof the chain, begin number

10、ing at the end providing thelowest number sequence at the first point of difference.When two equal chains compete for selection as basechain, choose the one with the greatest number ofsubstituents.Indicate and number the longest continuouscarbon chain in the molecule shown above.2. Number the atoms

11、in the chain, beginning at the endnearer the first substituent on the chain. If there aresubstituents occurring at equal distances from both endsof the chain, begin numbering at the end providing thelowest number sequence at the first point of difference.When two equal chains compete for selection a

12、s basechain, choose the one with the greatest number ofsubstituents.Indicate and number the longest continuouscarbon chain in the molecule shown above.2. Number the atoms in the chain, beginning at the endnearer the first substituent on the chain. If there aresubstituents occurring at equal distance

13、s from both endsof the chain, begin numbering at the end providing thelowest number sequence at the first point of difference.When two equal chains compete for selection as basechain, choose the one with the greatest number ofsubstituents.Indicate and number the longest continuouscarbon chain in the

14、 molecule shown above.2. Number the atoms in the chain, beginning at the endnearer the first substituent on the chain. If there aresubstituents occurring at equal distances from both endsof the chain, begin numbering at the end providing thelowest number sequence at the first point of difference.Whe

15、n two equal chains compete for selection as basechain, choose the one with the greatest number ofsubstituents.The chain shown on the right is not selectedbecause it has fewer substituents.3. Substituents on the chain are named as alkyl radicals andare numbered using the numbering system from (2).Whe

16、n two or more substituents are identical, use themultipliers: di-, tri-, tetra-, etc. Names are to bearranged alphabetically without regard for thesemultiplier prefixes. Write the name as a single word,using hyphens to separate prefixes and commas toseparate numbers.Indicate and number the longest c

17、ontinuouscarbon chain in the molecule shown above.3. Substituents on the chain are named as alkyl radicals andare numbered using the numbering system from (2).When two or more substituents are identical, use themultipliers: di-, tri-, tetra-, etc. Names are to bearranged alphabetically without regar

18、d for thesemultiplier prefixes. Write the name as a single word,using hyphens to separate prefixes and commas toseparate numbers.Number and name the substituents.2,2,6-trimethyl4-propyl.arrange these alphabetically and write the name.3. Substituents on the chain are named as alkyl radicals andare nu

19、mbered using the numbering system from (2).When two or more substituents are identical, use themultipliers: di-, tri-, tetra-, etc. Names are to bearranged alphabetically without regard for thesemultiplier prefixes. Write the name as a single word,using hyphens to separate prefixes and commas tosepa

20、rate numbers.2,2,6-trimethyl-4-propyloctanenot 3,7,7-trimethyl-5-propyloctane4. Complex substituents are numbered from the point ofattachment to the main chain and are included inparenthesis.Indicate and number the longest continuouscarbon chain in the molecule shown above.4. Complex substituents ar

21、e numbered from the point ofattachment to the main chain and are included inparenthesis.Number and name the substituents.2,3-dimethyl6-(2-methylpropyl).arrange these alphabetically and write the name.4. Complex substituents are numbered from the point ofattachment to the main chain and are included

22、inparenthesis.2,3-dimethyl-6-(2-methylpropyl)decaneor 6-isobutyl-2,3-dimethyldecane 烷烃的结构 实验事实 实验事实的解释及结构的确定 烷烃的结构实验事实1 甲烷的一取代物 CH3X，二取代物 CH2XY，三取代物 CHXYZ，均只有一种。2 烷烃中的碳是四价与基态碳电子排布有矛盾。3 烷烃化学性质不活泼无强烈条件一般不易发生化学反应。Valence of Common AtomsValence: the number of bonds an atom forms in its neutral ground-st

23、ate.Bonding in CarbonGround-state carbon has an electronic configurationof 2s2 2px1 2py1. In order to form four bonds, anelectron must be promoted from the 2s orbital to the2pz orbital.Bonding in CarbonThe Geometry of Carbon CompoundsThe Geometry of Carbon CompoundsThe Geometry of Carbon CompoundsGe

24、ometry of Tetravalent CarbonTetrahedral GeometryPossible Structures of DichloromethanePyramidal geometry would yield four structures.Tetrahedral geometry.Tetrahedral geometry would yield one structure. Identical structures.Possible Structures of DichloromethanePyramidal geometry would yield four str

25、uctures.Methane is Tetrahedral withDihedral angels of 109.5oThe Geometry of Carbon CompoundsAlkanesAlkanes represent the most basic functional groupwithin organic chemistry. They contain only carbonand hydrogen; all carbons are sp3 and all bond anglesare 109.5o.Orbital hybridization in alkanesRecall

26、 that an sp3 hybrid arises from thecombination of four atomic orbitals to form amolecular orbital with tetrahedral geometry.Methane (CH4) the simplest alkaneAgain, methane is tetrahedralwith dihedral angles of 109.5o. Bond property 1.沿轨道对称轴方向交盖，交盖程度大，所以牢固。 2. 可沿键轴自由旋转，不会影响电子云的交盖，因此不会破坏化学键。 3.由于碳的四个价

27、电子全部与C或H形成稳定的键了，所以化学性质不活泼。 烷烃的构象(Conformation) 1 构象定义 2 构象表示法 3 构象分析 Representations of carbon compounds Representations of carbon compounds Representations of carbon compounds Representations of carbon compounds Representations of carbon compounds Representations of carbon compounds 1. A CH2 is sho

28、wn as a simple vertex.2. A CH3 is shown as a truncated line.Representations of carbon compounds Representations of carbon compounds Representations of carbon compounds Representations of carbon compounds Representations of carbon compounds Because rotation around single bonds is rapid ( 106 sec-1),c

29、onformational isomers can not typically be separated andconformational isomers of a compound are all regarded asidentical forms.Convert the following structures into “line drawings”Convert the following line drawing into a “Newman Projection” 构象分析 基本思想：一个分子的总能量和它的几何形状直接相关，在有机化学中非键连的相互作用是很重要的，如原子间排斥和

30、吸引以及由于键长和键角的扭曲所引起的不稳定作用等。一个分子沿单键旋转形成分子中原子在空间的不同排列，这些不同排列称为构象异构体，构象分析就是分析各构象异构体的能量与几何形状的关系。 烷烃中非键连原子间相互作用主要为： （1）原子或基团间的Vander Weal半烃 交盖引起的空间张力。 （2）C-H键的电子间的相互斥力。Conformational IsomerismWe have seen previously that rotation around single bondsproduces compounds which differ in their spatialgeometry a

31、nd are referred to as Conformational Isomers.Because rotation around single bonds is rapid ( 106 sec-1),conformational isomer can not typically be separated andconformational isomers of a compound are all regarded asidentical forms. There are, nonetheless energy barriersassociated with these rotatio

32、ns.Rotation around the carbon-carbonsingle bond in ethaneHigh-energy, eclipsed conformation.Low-energy, staggered conformation.Rotation around the carbon-carbonsingle bond in ethaneHigh-energy, eclipsed conformation.Low-energy, staggered conformation.Conformational isomers of butaneConformational is

33、omers of butane“Newman-like” viewConformational isomers of butaneConformational isomers of butane 60orotationConformational isomers of butane 60orotation 120orotationConformational isomers of butane 60orotation 120orotation 180orotationConformational isomers of butane 60orotation 120orotation 180oro

34、tation 240orotationConformational isomers of butane 60orotation 120orotation 180orotation 240orotation 300orotationConformational isomers of butaneeclipsedgaucheeclipsedeclipsedgaucheantigauchegaucheantiPhysical properties of simple alkanesFor simple straight-chain alkanes, boiling and meltingpoints

35、 generally increase with increasing chain length.The dependence of the boiling and melting points on chainlength can be explained in terms of increasing attractive vander Walls interactions as the chain length increases.烷烃的化学性质 只讲取代反应，其他反应自学 实验事实（1）（2）（3）（4）（5） 反应机理 反应取向 反应活性与选择性 反应活化能与过渡态 实验事实： (1)

36、CH4与Cl2在暗处或室温下不反应。 (2)温度高于250时，CH4与Cl2在暗处可以反应。 (3)室温下，CH4与Cl2 在紫外光照射下反应。 (4)当反应由光引发时，体系每吸收一个光子可得 到几千个氯甲烷分子。 (5)少量氧使反应延迟开始，延迟时间与氧的量有关。 反应机理 对一个化学反应的详细描述称为反应机理（反应历程）。机理仅仅是一种假说，是为了说明事实而提出来的。当有更多的事实被发现时，这个机理也能解释它们，否则为了解释它们，就应对这个机理进行修改，必要时甚至可以抛弃这个机理而提出新机理。结论 所以20H比10H活性高四倍，但是由于 10H数量多而使取代产物中，二者的差距不大。 30H活泼说明（CH3)C自由基易生成。我们知道化合物越稳定越易生成 ，进而得出自由基稳定次序： (CH3)3C (CH3)