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第五章 芳香烃 Aromatic compounds

第五章 芳香烃 Aromatic compounds. 概述. 1. 脂肪烃及芳香烃. Aliphatic and aromatic compounds 芳香性 Aromaticity. KMnO 4. ×. +Br 2 /CCl 4. ？. ×. +Br 2 / FeBr 3. Aromaticity 芳香性 稳定的环，易取代，难加成，难氧化. 2. 烷基苯工业来源（ Industrial source of alkylbenzenes ）. Coal Petroleum （见书 第四节 ）. Coke( 焦炭）. △ （ no air).

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第五章 芳香烃 Aromatic compounds

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  1. 第五章 芳香烃Aromatic compounds

  2. 概述

  3. 1.脂肪烃及芳香烃 • Aliphatic and aromatic compounds • 芳香性Aromaticity

  4. KMnO4 × +Br2/CCl4 ？ × +Br2/ FeBr3 Aromaticity 芳香性 稳定的环，易取代，难加成，难氧化

  5. 2.烷基苯工业来源（ Industrial source of alkylbenzenes ） • Coal • Petroleum • （见书第四节）

  6. Coke(焦炭） △（no air) • Coal • Coal tar(煤焦油)+ Coal gas Benzene,toluene,xylenes,phenol cycloalkanes Aromatic hydrocarbon Catalytic reforming 催化重整

  7. 煤焦油的分馏产物 馏分名称 沸点范围/℃ 主要成分 轻油 <180 苯、甲苯、二甲苯 酚油 180~210 苯酚、甲苯酚等 萘油 210~230 萘、甲基萘等 洗油 230~300 联苯、苊、芴等 蒽油 300~360 蒽、菲等 沥青 >360 沥青、游离碳

  8. 3.分类 • 单环芳烃 • 多环芳烃 • 非苯芳烃

  9. 第一节 单环芳烃 • 苯及同系物（ benzene and homolog ）

  10. 一.苯的结构 （structure of benzene） • 1.开库勒结构式（ Kekule structure） • In 1825 M.Faraday • In 1834 E.Mitscherlich • In 1865 August Kekule

  11. August Kekule • I was sitting writing at my textbook,but the work did not progress;my thoughts were elsewhere. I turned my chair to the fire,and dozed.Again the atoms were gamboling before my eyes.This time the smaller groups kept modestly in the beckground.My mental eye,rendered more acute by repeated visions of this

  12. kind,could now distinguish larger structures of manifold conformations;long rows,sometimes more closely fitted together;all twisting and turning in snake-like motion.But look!What was that?One of the snakes had seized hold of its own tail,and the form whirled mockingly before my eyes.As if by a flash of lightning I woke;……I spent the rest of the night working out the consequences of the hypothesis. Let us learn to dream,gentlemen,and then perhaps we shall learn the truth.

  13. August Kekule • 苯环结构的诞生是有机化学发展史上的一块里程碑

  14. Kekule formula

  15. Dewar formula

  16. 2.轨道理论Theory of orbit • C —SP2

  17. （1） C sp2 hybridized （2） Particularly stable （3）电子离域 Electron Delocalization

  18. CH3—CH3 Csp3-Csp3154 pm CH2=CH—CH3 Csp2-Csp3150 pm CH2=CH—CH=CH2 Csp2-Csp2146 pm C6H6 Csp2-Csp2 139 pm

  19. 3.分子轨道理论Theory of molecular orbit

  20. 4.共振（ Resonance structure of benzene ） Resonance Contributors

  21. Linus pauling

  22. 电子离域与共振 Electron Delocalization and Resonance • p-electrons in conjugated dienes and benzene are delocalized • 定域电子：被限制在两个原子核区域内运动的电子 • 离域电子：不局限于两个原子核区域内运动的电子 • 这种电子的离域作用我们也称之为共轭作用 • 上述非经典结构式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（共振极限结构）来表示。

  23. How to drow resonance contributors In order to draw contributors, the electrons in one resonance contributor are moved to generate the next contributor. Rules for Drawing Resonance Contributors • Only electrons move. The nuclei of the atoms never move • The only electrons that can move are π electrons and nonbonding electrons • The total number of electrons in the molecule does not change, neither do the numbers of paired and unpaired electrons

  24. The electrons can be moved in one of the following ways （1） Move πelectrons toward a positive charge

  25. （2）Move πelectrons toward a π bond

  26. （3） Move a nonbonding pair of electrons toward a πbond

  27. （4） Move a single nonbonding electron toward a πbond

  28. 共振杂化体比它的任何一个共振式都要稳定 • 共价键数目越多的共振式越稳定 • 共振式中的电荷越分散就越稳定 • 越稳定的共振式对共振杂化体的贡献越大 1, 3-butadiene

  29. （5）相对稳定的共振式的数目越多，共振杂化体越稳定（5）相对稳定的共振式的数目越多，共振杂化体越稳定

  30. （6）共振式越接近等价，共振杂化体越稳定

  31. 二.命名Nomenclature • 1. 简单 • ×× 苯 （ ×× benzene） Chlorobenzene Nitrobenzene

  32. Special names Toluene Aniline

  33. 2. 相对复杂 苯乙烯 Styrene phenylethylene 2-苯基戊烷 2－phenylpentane

  34. 3.多取代基 p-Dibromobenzene para O-Dibromobenzene ortho m-Dibromobenzene meta

  35. 2-氯-3-硝基苯磺酸 2-chloro-3-nitrobenzene-sulfonicacid 优先次序： -COOH ， -SO3H ， -CN ， -CHO，>C=O，-OH，-NH2，-R，- X ， NO2

  36. 三、物理性质 • 苯：无色透明,易燃液体。 • 不溶于水。遇热、明火易燃烧、爆炸。 • 能与氧化剂, 发生剧烈反应。 • 蜡、树脂、油的溶剂; • 合成化学制品和制药的中间体。汽油一种成份,含量<2% • 急性苯中毒：麻醉作用 • 慢性中毒

  37. 四、化学性质 （一）芳香亲电取代反应 （electrophilic aromatic substitution reactions）

  38. +Br2/ FeBr3

  39. 机理 Mechanism: Step 1: Step 1: Step 2: ：

  40. Reaction coordinate diagrams:

  41. 1.卤代Halogenation Bromobenzene Catalyst:FeCl3, AlCl3, CuCl2, SbCl5

  42. FeBr3 + Br2 → FeBr4- + Br+

  43. diazepam

  44. 2.硝化Nitration Nitrobenzene

  45. 硝基苯 • 硝基苯; 密斑油; 苦杏仁油 • 相对密度1.205。难溶于水 • 硝基苯的主要毒作用

  46. 3.磺化Sulfonation —— reversible reaction 苯磺酸Benzenesulfonic acid

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