2. Chapter 13 Aromatic compounds 13.1 Introduction 1.How to find benzene? 2.Kekule( 克库勒） was the first to recognize that these early aromatic compounds all contain a six-carbon unit. Benzene 苯

3. 13.2 Nomenclature of benzene Derivatives

5. Monosubstituted benzenes

6. When two substituents are present, their relative positions are indicated by the prefixes ortho, meta, and para (abbreviated o-, m-, and p-) or by the use of numbers.

7. Nitrobenzoic acids 硝基苯甲 酸

8. The dimethylbenzenes are called xylenes ( 二甲苯）

9. If more than two groups are present on the benzene ring, their positions must be indicated by the use of numbers.

10. The new parent name is used

11. When the C 6 H 5 - group is named as a substituent, it is called a phenyl group (ph-).

12. The phenyl group is often abbreviated as C 6 H 5 -, Ph-. The name benzyl is an alternative name for the phenylmethyl group:

13. 13.3 Reactions of benzene

14. 13.4 The Kekule Structure for benzene 苯的克库勒结构 In 1865 ， Kekule, the originator of the structural theory, proposed the first definite structure for benzene, a structure that is still used today. Kekule suggested that the carbon atoms of benzene are in a ring, that they are bonded to each other by alternating single and double bonds, that one hydrogen atom is attach to each carbon atom.

15. The Kekule formula for benzene 苯的克库勒式

17. 13.5 The stability of benzene 苯的稳定性

18. Fig. Relative stabilities 相对稳定 性

19. 13.6 Modern theories of the structure of benzene 13.6A the resonance explanation of the structure of benzene ( 苯环结构的共振理论解 释）

20. 13.6B The molecular orbital explanation of the structure of benzene （苯结构的分子轨道理 论解释）

21. Fig. 13.3 Overlapping p orbitals in benzene ( 苯的 p 轨道 的重叠）

22. Fig. 13.4 How six p atomic orbital combine to form six pi- molecular orbitals

23. Fig. 13.5 Shapes of the pi-molecular orbitals of benzene as viewed from down

24. 13.7 HUCKEL’S Rule( 休克尔规 则） : The (4n+2) pi-Electron Rule Conditions ; 1.The (4n+2) pi-electron ， where n=1,2,3--- 2.Planar monocyclic ring conjugate system ( 平面单环共轭体系） 符合这两个条件的环具有芳香性 （ Aromatic), 具有芳香性的物质，是稳 定的。化学性质表现出难加成，易取代。

25. For example

26. 13.7A The Annulenes （轮 烯） The name annulene has been proposed as a general name for monocyclic compounds that can be represented by structures having alternating single and double bonds.

29. Cyclobutadiene is a 4n molecule not a 4n+2 molecule, and as we would expect, it is a highly unstable compound and it is not aromatic.

30. 13.7B Aromatic Ions 芳香离 子 Cyclopentadiene is not aromatic; however, it is unusually acidic for a hydrocarbon. Because of its acidity, cyclopentadiene can be converted to its anion by treatment with moderately strong bases.

32. Cycloheptatriene ( 环庚三烯）

33. 13.8 Other aromatic compounds 13.8A benzenoid aromatic compounds ( 苯 形芳香化合物） Representatives of one broad class of aromatic compounds called polycyclic benzenoid aromatic hydrocarbons.

35. According to resonance theory, a molecule of naphthalene can be considered to be a hybrid of three Kekule structure.

36. Fig. 13.2 The p orbitals of naphthalene

38. 13.8B Nonbenzenoid aromatic compounds 非苯型的芳香族化合 物

39. 13.9 Reduction of aromatic compounds: The Birch reduction 伯奇还原

40. 13.9A The Birch reduction 伯奇还原 Benzene can be reduced to 1,4- cyclohexadiene by treating it with an alkali metal(sodium (Na), lithium (Li), or potassium (K)) in a mixture of liquid ammonia and alcohol.

41. The Mechanism of Birch reduction 伯奇还原的机理

42. Dissolving metal reductions of this type were developed by the Australian chemist A.J. Birch and have come to be known as Birch reductions

43. Reduction of 1,2- dimethylbenzene (o-xylene 邻 - 二甲苯 )

44. Birch reduction of sodium benzoate

45. 13.10 Benzylic radicals and cations Removal of a hydrogen atom from the methyl group of methylbenzene (Toluene) produces a radical called the benzyl radical ( 苄基自由基） Benzylic radicals and benzylic cations are conjugated unsaturated systems and both are stable.

46. This exceptional stability of benzylic radicals and cations is easily explained by resonance theory.

47. Benzylic cations are stabilized by resonance

48. 13.11 Allylic and benzylic halides in nucleophilic substitution reactions ( 亲核取代反应中的烯丙基卤和苄 基卤）（不讲）

49. 13.12 Heterocyclic aromatic compounds ( 杂环芳香族化合 物） Heterocyclic compounds containing nitrogen, oxygen, or sulfur are by far the most common. Four important examples are given here in their KeKule forms. These four compounds are all aromatic.

50. The nitrogen atoms in molecules of both pyridine and pyrrole are sp 2 hybridized.

51. 13.17 The orbital structures of furan and thiophene The oxygen and sulfur atoms of furan and thiophene carry an Unshared pair of electrons in an sp 2 orbital that is orthogonal to the πsystem.

52. 13.13 Aromatic compounds in biochemistry Two amino acids necessary for protein synthesis contain the benzene ring:

54. Homework P 548 Additional Problems 13.22, 13.23, 13.28