文本案例課件ch2upload-1alkanes

1、Chapter 2 Alkanes2013 Wei Dong Nanjing University of Science & Technology All Rights ReservedContents 烴的分類 烷烴的通式，同系列和構(gòu)造異構(gòu) 烷烴的命名 烷基的概念 （1）伯、仲、叔碳和伯、仲、叔氫 （2）烷基 烴的分類 烷烴 開鏈烴（脂肪烴） 烯烴 烴 炔烴 閉鏈烴 脂環(huán)烴 （環(huán)烴） 芳香烴 有機(jī)化學(xué)的基礎(chǔ)是結(jié)構(gòu)理論，進(jìn)行上面分類的依據(jù)是它們的結(jié)構(gòu)不同，今后我們按照這樣的分類逐類進(jìn)行學(xué)習(xí)。在學(xué)習(xí)每一類有機(jī)化合物時要搞清楚兩方面內(nèi)容： （1）一類化合物在結(jié)構(gòu)與性質(zhì)上有什么特征。 （2）這類化合

2、物中結(jié)構(gòu)與性質(zhì)是怎樣變化的。 要求：不要僅僅記住這些事實，而是一有 可能便試圖通過結(jié)構(gòu)理解這些性質(zhì)，并且 根據(jù)結(jié)構(gòu)的差異來解釋性質(zhì)的差異。烷烴的通式和構(gòu)造異構(gòu) 碳原子數(shù) 結(jié)構(gòu)式 分子式 名稱 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 異丁烷 isobutane CH3 經(jīng)考察發(fā)現(xiàn)烷烴有如下三個規(guī)律： (1) 烷烴異構(gòu)數(shù)目隨碳原子數(shù)增加而增加。 (2) 烷烴分子的通式為CnH2n+2。 (

3、3) 相鄰兩個烷烴的分子式都相差一個CH2。烷基的概念 R，Radical；Residue 碳原子數(shù) 烷烴 烷基 名稱 Name 縮寫 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 異丙基 iso-propyl i-pr 碳原子數(shù) 烷烴 烷基 名稱 Name 縮寫 4 CH3CH2CH2CH3 CH3CH2CH2CH2 正丁基 n-butyl n-Bu CH3CHCH2 CH3 異丁基 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 烷烴的命名 習(xí)慣命名法 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 烷烴的結(jié)構(gòu) 實驗事實 實驗事實的解釋及結(jié)構(gòu)的確定 烷烴的結(jié)構(gòu)實驗事實1 甲烷的一取代物 CH3X，二取代物 CH2XY，三取代物 CHXYZ，均只有一種。2 烷烴中的碳是四價與基態(tài)碳電子排布有矛盾。3 烷烴化學(xué)性質(zhì)不活潑無強(qiáng)烈條件一般不易發(fā)生化學(xué)反應(yīng)。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.沿軌道對稱軸方向交蓋，交蓋程度大，所以牢固。 2. 可沿鍵軸自由旋轉(zhuǎn)，不會影響電子云的交蓋，因此不會破壞化學(xué)鍵。 3.由于碳的四個價

27、電子全部與C或H形成穩(wěn)定的鍵了，所以化學(xué)性質(zhì)不活潑。 烷烴的構(gòu)象(Conformation) 1 構(gòu)象定義 2 構(gòu)象表示法 3 構(gòu)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 “l(fā)ine drawings”Convert the following line drawing into a “Newman Projection” 構(gòu)象分析 基本思想：一個分子的總能量和它的幾何形狀直接相關(guān)，在有機(jī)化學(xué)中非鍵連的相互作用是很重要的，如原子間排斥和

30、吸引以及由于鍵長和鍵角的扭曲所引起的不穩(wěn)定作用等。一個分子沿單鍵旋轉(zhuǎn)形成分子中原子在空間的不同排列，這些不同排列稱為構(gòu)象異構(gòu)體，構(gòu)象分析就是分析各構(gòu)象異構(gòu)體的能量與幾何形狀的關(guān)系。 烷烴中非鍵連原子間相互作用主要為： （1）原子或基團(tuán)間的Vander Weal半烴 交蓋引起的空間張力。 （2）C-H鍵的電子間的相互斥力。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.烷烴的化學(xué)性質(zhì) 只講取代反應(yīng)，其他反應(yīng)自學(xué) 實驗事實（1）（2）（3）（4）（5） 反應(yīng)機(jī)理 反應(yīng)取向 反應(yīng)活性與選擇性 反應(yīng)活化能與過渡態(tài) 實驗事實： (1)

36、CH4與Cl2在暗處或室溫下不反應(yīng)。 (2)溫度高于250時，CH4與Cl2在暗處可以反應(yīng)。 (3)室溫下，CH4與Cl2 在紫外光照射下反應(yīng)。 (4)當(dāng)反應(yīng)由光引發(fā)時，體系每吸收一個光子可得 到幾千個氯甲烷分子。 (5)少量氧使反應(yīng)延遲開始，延遲時間與氧的量有關(guān)。 反應(yīng)機(jī)理 對一個化學(xué)反應(yīng)的詳細(xì)描述稱為反應(yīng)機(jī)理（反應(yīng)歷程）。機(jī)理僅僅是一種假說，是為了說明事實而提出來的。當(dāng)有更多的事實被發(fā)現(xiàn)時，這個機(jī)理也能解釋它們，否則為了解釋它們，就應(yīng)對這個機(jī)理進(jìn)行修改，必要時甚至可以拋棄這個機(jī)理而提出新機(jī)理。結(jié)論 所以20H比10H活性高四倍，但是由于 10H數(shù)量多而使取代產(chǎn)物中，二者的差距不大。 30H活潑說明（CH3)C自由基易生成。我們知道化合物越穩(wěn)定越易生成 ，進(jìn)而得出自由基穩(wěn)定次序： (CH3)3C (CH3)