附件2 粒大浮 教 案 2003~~2004学年第Ⅰ学期 院(系、所、部)化学与环境学院有机化学研究所 教研室有机化学 课程名称有机化学(双语教学 授课对象化学教育 授课教师杨定乔 职称职务教授 教材名称 Organic Chemistry 2003年09月01日
附件 2 教 案 2003~~ 2004 学年 第 I 学期 院（系、所、部）化学与环境学院有机化学研究所 教 研 室 有机化学 课 程 名 称 有机化学(双语教学) 授 课 对 象 化学教育 授 课 教 师 杨定乔 职 称 职 务 教授 教 材 名 称 Organic Chemistry 2003 年 09 月 01 日
有机化学(双语教学)课程教案 授课题目(教学章节或主题):第七章·芳烃授课类型理论课 Aromatic Compounds 授课时间第8周第29-36节 教学目标或要求:了解苯的结构及芳烃的异构现象和苯环的亲电取代定位效应的基本 理论。掌握苯环的亲电取代反应及其反应机理 教学内容(包括基本内容、重点、难点) Arenes Nomenclature Monosubstituted benzene derivatives are names as other hy drocarbons using the following set of rules 1. Benzene is the parent name; when a benzene ring is a substituent on another chain, it is referred to as a CH3 methylbenzene 1-pheny]heptane bromobenzene ethylbenzene or toluene 2. Disubstituted benzenes are named using ortho para-and meta- to describe the substitution pattern (1, 2 1, 4 and 1, 3 respectively or simply by num bering the substituents
有机化学(双语教学) 课程教案 授 课 题 目（ 教 学 章节 或 主题 ）：第 七 章 ．芳 烃 （Aromatic Compounds） 授课类型 理论课 授课时间 第 8 周第 29-36 节 教学目标或要求：了解苯的结构及芳烃的异构现象和苯环的亲电取代定位效应的基本 理论。掌握苯环的亲电取代反应及其反应机理。 教学内容（包括基本内容、重点、难点）： Arenes: Nomenclature Monosubstituted benzene derivatives are names as other hydrocarbons using the following set of rules: 1. Benzene is the parent name; when a benzene ring is a substituent on another chain, it is referred to as a "phenyl" group. 2. Disubstituted benzenes are named using ortho-, para- and meta- to describe the substitution pattern (1,2 1,4 and 1,3 respectively) or simply by numbering the substituents
1, 3-diethylbenzel CH2CH3 ortho-dibromobenze para-dimethylbenzene or 1.2-dibromoben 1, 4-dimethylbenzene or para-Iylene 3. Substituents are num bered to give the lo west possib le num ber sequence at the first point of difference assigning priorities alphabetically if there is a"tie". 1-chloro-3, 5-diethylbenzene There are also a large number of common (or trivial") names for arenes which are in common usage and students should strive to recognize these by both systematic and common names H NH. H aniline phenol nitrobenzene is these is used as the parent chain, the substituent is position #1, br he Many of these are acceptable parents" with regard to nomenclature. When definit
3. Substituents are numbered to give the lowest possible number sequence at the first point of difference, assigning priorities alphabetically if there is a "tie". There are also a large number of common (or "trivial") names for arenes which are in common usage and students should strive to recognize these by both systematic and common names. Many of these are acceptable "parents" with regard to nomenclature. When one is these is used as the parent chain, the substituent is position #1, by definition
CH3 2-chloro- nitrotoluene 2 chloro-4-nitrotolpene H NO 5chloro-2-nitrotolpene More examples: 4-bromo-12-dime thylbenzene 3chloro-1-me thylbenzene au l-methyl-4-nitrobenzene cu nitrotoluene 2-chloro-1-ethyh4-nitrobenzene l-chloro-2-ethyh-nitrobemzene 4chloro-2-ethyhI-nitrobenzene Arenes: Aromatic Systems and the 4n+2 Rule
More Examples: Arenes: Aromatic Systems and the 4n+2 Rule
Benzene, having the molecular formula C h, would be consistent with a structure such as cyclohexatriene, having three con jugated double bonds in a six-membered ring. The compound is, however, far more stable than would be predicted for a triene, based on the heat of hydrogenation (the energy evolved when one mole of compound is reacted with H, in the presence of Pt or Pd catalyst. As shown below, the inclusion of additional double bonds in a compound is generally associated with an increase in the heat of hydrogenation of approximately 25 kcal/mole; benzene, however, has a heat of hydrogenation which is less than that of cyclohexadiene. Further, benzene does not undergo typical alkene reactions; it will not react with Br, to form a dibromide, nor will it react with halogen acids (i. e, Hcl) to give alkyl halides Heat of Hydrogenation (energy released duning reduction with HyPt Reactant Prodnct AH° Cyclohexene Cyclohexane 28.6 kcallmole 1 3-Cyclohexadieneene Cyclohexane 55.4 kcal'mole Cyclone xane 49.8 kcal mole H2iPt 86 kcal' mole expected: 50 kcallmole observed 36 kcalhmole more stable than expected The rationalization for the unusual reactivity of benzene which is generally accepted today is that the conjugated T-system forms a continuous molecular orbital above and below the plane of the ring, and that this planar, continuous T-System containing six electrons has unusual stability. The delocalization of the electrons is typically shown by writing resonance forms in which the double bonds in benzene compounds can be shown to be distributed equally among 11 carbon centers (shown below for dibromobenzene). Remember that resonance forms represent structural limits and that the molecule is"never"one form or the other but is a hybrid of both. To show this, the bonding in benzene compounds is often written as a circle within the ring, although this type of structural representation has its own drawbacks, as we will see when we consider substitution reactions
Benzene, having the molecular formula C6H6, would be consistent with a structure such as cyclohexatriene, having three conjugated double bonds in a six-membered ring. The compound is, however, far more stable than would be predicted for a triene, based on the heat of hydrogenation (the energy evolved when one mole of compound is reacted with H2 in the presence of Pt or Pd catalyst. As shown below, the inclusion of additional double bonds in a compound is generally associated with an increase in the heat of hydrogenation of approximately 25 kcal/mole; benzene, however, has a heat of hydrogenation which is less than that of cyclohexadiene. Further, benzene does not undergo "typical" alkene reactions; it will not react with Br2 to form a dibromide, nor will it react with halogen acids (i.e., HCl) to give alkyl halides. The rationalization for the unusual reactivity of benzene which is generally accepted today is that the conjugated −system forms a continuous molecular orbital above and below the plane of the ring, and that this planar, continuous −system containing six electrons has unusual stability. The delocalization of the electrons is typically shown by writing resonance forms in which the double bonds in benzene compounds can be shown to be distributed equally among all carbon centers (shown below for dibromobenzene). Remember that resonance forms represent structural limits and that the molecule is "never" one form or the other, but is a hybrid of both. To show this, the bonding in benzene compounds is often written as a circle within the ring, although this type of structural representation has its own drawbacks, as we will see when we consider substitution reactions
The formation of the molecular orbital can be seen be low, as the overlap of the six p-orbitals to form the continuous T-system The resonance description of benzene explains the geometry of the molecule but does not explain the unusual stability of benzene and its derivatives. The stability of benzene is suggested to arise from the fact that the conjugated T-system is planar and contains 4n +2 electrons (withn = 1), and it: suggested that all compounds having planar, conjugated ?systems containing An+2 electrons will share this stability. This property, described originally by Huckel, is referred to as aromaticity. Aromaticity, and unusual stability, will therefore be associated with molecules having 6(n =1), 10(n =2),14 (n=3), 18(n =4), etc, electrons. Unshared pairs of electrons on heteroatoms within the ring can also be counted to achieve aromaticity, as shown in the examples belo 4 electrons 6 electrons aromatic not aromatic Adenine. Uracil- 6 electrons 6 electrons 10 electrons 6 electron Aromatic Aromatic It is also essential that the carbon skeleton be planar, as shown for cyclodecapentaene, which has 10 T-electrons, but is not aromatic because the ring hydrogens force the T-system out of planarity
The formation of the molecular orbital can be seen below, as the overlap of the six p-orbitals to form the continuous −system. The resonance description of benzene explains the geometry of the molecule but does not explain the unusual stability of benzene and its derivatives. The stability of benzene is suggested to arise from the fact that the conjugated −system is planar and contains 4n + 2 electrons (with n = 1), and it is suggested that all compounds having planar, conjugated ?systems containing 4n + 2 electrons will share this stability. This property, described originally by Huckel, is referred to as aromaticity. Aromaticity, and unusual stability, will therefore be associated with molecules having 6 (n = 1), 10 (n = 2), 14 (n = 3), 18 (n = 4), etc., electrons. Unshared pairs of electrons on heteroatoms within the ring can also be counted to achieve aromaticity, as shown in the examples below: It is also essential that the carbon skeleton be planar, as shown for cyclodecapentaene, which has 10 −electrons, but is not aromatic because the ring hydrogens force the −system out of planarity
Cyclodecapentaene Lack of planarity is not a problem in [18]annulene(18 T-electrons: 4n +2 where 4), where there is sufficient room for the central six hydrogen atoms to fit within the middle of the ring system. [8]Annulene 18-ntelectrons 48+2 where p=4 Arenes: Reactions of Ary l Side-Chains Arenes having an alkyl side-chain with at least one benzylic hydrogen will undergo oxidation in the presence of neutral MnO. anion to give the corresponding benzoic acid. Note that in the example given below, the same product(benzoic acid)is produced by all three reactions, with the remaining carbons appearing as secondary oxidation products. As with all reactions involving MnO,, the reaction involves radical intermediates and side reactions are common
Lack of planarity is not a problem in [18]annulene (18 −electrons; 4n +2 where n = 4), where there is sufficient room for the central six hydrogen atoms to fit within the middle of the ring system. Arenes: Reactions of Aryl Side-Chains Arenes having an alkyl side-chain with at least one benzylic hydrogen will undergo oxidation in the presence of neutral MnO4 - anion to give the corresponding benzoic acid. Note that in the example given below, the same product (benzoic acid) is produced by all three reactions, with the remaining carbons appearing as secondary oxidation products. As with all reactions involving MnO4 -, the reaction involves radical intermediates and side reactions are common
Mno4 /H2o, heat CH2CH2CH3 Mno, / H2O, heat . benzylic carbon Mno4 /H2o, heat must have at least one Alky l-substituted ary sulfonic acids undergo a somewhat brutal reaction know as alkali fusion in which the sulfonic acid residue is replaced by a hydroxy l group, yielding a substituted phenol. Because of the extreme reaction conditions, the reaction is limited to simple compounds, but is a useful pathway to forming phenols sO,H alkyl-substituted benzenes only Since benzyl radicals are quite stable(being resonance-stabilized by the adjacent ring), free radical bromination occurs quite rapidly on alkyl benzenes having at least one benzylic hydrogen. The reaction conditions employed often utilize NBS(N-bromosuccinimide) in CCl, in the presence of a radical initiator to generate the bromine radical
Alkyl-substituted arylsulfonic acids undergo a somewhat brutal reaction know as "alkali fusion" in which the sulfonic acid residue is replaced by a hydroxyl group, yielding a substituted phenol. Because of the extreme reaction conditions, the reaction is limited to simple compounds, but is a useful pathway to forming phenols. Since benzyl radicals are quite stable (being resonance-stabilized by the adjacent ring), free radical bromination occurs quite rapidly on alkyl benzenes having at least one benzylic hydrogen. The reaction conditions employed often utilize NBS (N-bromosuccinimide) in CCl4 in the presence of a "radical initiator" to generate the bromine radical
NBSIC radical H2CH3 radical initiato NB S/CCl4 radical initiator ◎Q Since arenes are resistant to catalytic reduction, alkene side-chains can be specifically reduced to the alkane without reducing the ring. If you want to reduce the ring, high temperatures and pressure are required when standard catalysts are utilized(Pt or Pd), although Rh will catalyze the reduction under very mild conditions. HolD Ho, RhC 25°c,1at H,, PtC 250C;1atm Catalytic reduction will also reduce aryl nitro groups to the corresponding amine(or, specific reduction can be accomplished using acidic SnCl). Likewise, aryl ketones are smoothly reduced catalytically to give the corresponding alkane. This latter reaction is quite often useful since an alkyl chain which would be prone to rearrangement in a Friedel-Crafts alkylation can be introduced using an acylation, and then simple reduced to the alkane
Since arenes are resistant to catalytic reduction, alkene side-chains can be specifically reduced to the alkane without reducing the ring. If you want to reduce the ring, high temperatures and pressure are required when standard catalysts are utilized (Pt or Pd), although Rh will catalyze the reduction under very mild conditions. Catalytic reduction will also reduce aryl nitro groups to the corresponding amine (or, specific reduction can be accomplished using acidic SnCl2). Likewise, aryl ketones are smoothly reduced catalytically to give the corresponding alkane. This latter reaction is quite often useful since an alkyl chain which would be prone to rearrangement in a Friedel-Crafts alkylation can be introduced using an acylation, and then simple reduced to the alkane
HttPd 25°c,1atm CllHa' H2/Pd 25°C,1atm 教学手段与方法:课堂讲授 思考题、讨论题、作业:第548面: Additional Problems;13.22-13.28) 参考资料(含参考书、文献等) 1. Solomons. Organic Chemistry fifth adition 2. Oxford; Organic Chemistry 3.北京大学,有机化学 4.南京大学,有机化学,(上,下) 5.邢其毅,有机化学,(上,下) 注:1、每项页面大小可自行添减;2一次课为一个教案;3、“重点”、“难点”、“教学手段 与方法”部分要尽量具体;4、授课类型指:理论课、讨论课、实验或实习课、练习或习题 课等
教学手段与方法：课堂讲授 思考题、讨论题、作业：第 548 面: Additional Problems; 13.22-13.28) 参考资料（含参考书、文献等）： 1. Solomons, Organic Chemistry, fifth adition 2. Oxford; Organic Chemistry 3. 北京大学， 有机化学 4．南京大学， 有机化学，（上，下） 5．邢其毅，有机化学， （上，下） 注：1、每项页面大小可自行添减；2 一次课为一个教案；3、“重点”、“难点”、“教学手段 与方法”部分要尽量具体；4、授课类型指：理论课、讨论课、实验或实习课、练习或习题 课等