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):第四章炔烃与二烯|授课类型|理论课 烃( Alkynes and Dienes) 第4周第13-16 授课时间 教学目标或要求:了解炔烃的结构理论以及炔烃的化学性质。掌握共轭效应和亲电加 成理论 教学内容(包括基本内容、重点、难点) Reactions of alkynes Addition of Halogen Acids to Alkenes The addition of halogen acids to alkynes is a stepwise process which involves a solvent-equilibrated carbocation intermediate. The formation of this intermediate is initiated through a simple acid-base equilibrium in which the halogen acid donates a proton to the alkyne T-system, which is functioning as a Lewis base. The protonated T-system has a short lifetime and can rapidly revert to starting materials, or can rearrange from a(cationic) protonated T-bond, to an sp= sigma bond adjacent to an sp carbocation center. If the alkyne is unsymmetrical, the protonated T-cloud intermediate can break down by two pathways to potentially form carbocations having differing ground-state energies. The reaction pathways leading from this intermediate to the two carbocations will differ in energy, and, in general, the pathway leading to the more stable intermediate will be of lower energy and will be the preferred is best able to stabilize the cationic center. In simple unstrained e which pathway. The resulting carbocation is formed on the carbon of the alkyne which non-conjugated systems, without adjacent heteroatoms, the order of stability of carbocations formed from alkyne protonation will be secondary primary Since secondary centers have no attached and primary centers have one, there is an apparent inverse relationship between the number of attached hydrogens and the likelihood that the carbocation will form at that center and this is
有机化学（双语教学） 课程教案 授课题目（教学章节或主题）：第四章．炔烃与二烯 烃（Alkynes and Dienes） 授课类型 理论课 授课时间 第 4 周第 13-16 节 教学目标或要求：了解炔烃的结构理论以及炔烃的化学性质。掌握共轭效应和亲电加 成理论。 教学内容（包括基本内容、重点、难点）： Reactions of Alkynes Addition of Halogen Acids to Alkenes The addition of halogen acids to alkynes is a stepwise process which generally involves a solvent-equilibrated carbocation intermediate. The formation of this intermediate is initiated through a simple acid-base equilibrium in which the halogen acid donates a proton to the alkyne -system, which is functioning as a Lewis base. The protonated -system has a short lifetime and can rapidly revert to starting materials, or can rearrange from a (cationic) protonated -bond, to an sp2 sigma bond adjacent to an sp2 carbocation center. If the alkyne is unsymmetrical, the protonated -cloud intermediate can break down by two pathways to potentially form carbocations having differing ground-state energies. The reaction pathways leading from this intermediate to the two carbocations will differ in energy, and, in general, the pathway leading to the more stable intermediate will be of lower energy, and will be the preferred pathway. The resulting carbocation is formed on the carbon of the alkyne which is best able to stabilize the cationic center. In simple unstrained non-conjugated systems, without adjacent heteroatoms, the order of stability of carbocations formed from alkyne protonation will be secondary > primary. Since secondary centers have no attached and primary centers have one, there is an apparent inverse relationship between the "number of attached hydrogens" and the likelihood that the carbocation will form at that center and this is
another example of Markovnikoy's Rule, which was described for alkenes Once the carbocation is formed. the most favorable reaction will involve the addition of a nucleophile to form a viny l halide intermediate. This alkene can now undergo a second protonation step, just like any other alkene, except that the carbocation will always be formed on the carbon bearing the halogen, since this carbocation is now stabilized by resonance with the halonium ion. The final result of the addition is that two moles of halogen halide are added, to give a 1.1-dihalide HC≡ 2 HCI H-CH2 stepwise addition of Ao mer ofHX Markovnikov region hemistry Addition of Halogen to Alkynes The addition of halogen to alkynes is a stepwise process involving a"halonium ion intermediate. The formation of this intermediate is initiated through attack of halogen on the alkyne T-system, to form the cyclic halonium ion(i.e bromonium or chloronium ion) and expel the halogen anion (i.e, bromide or chloride). This intermediate is highly electrophilic and reacts rapidly with the best nucleophile in the system; that is, the halide anion expelled in the previous step. Attack by halide generates a viny l halide, which is an alkene and can undergo a second addition of halogen. The final product of the reaction is therefore a 1,1.2.2-tetrahalide had HgC H3 stepwise addition of nso maer of x2
another example of Markovnikov's Rule, which was described for alkenes. Once the carbocation is formed, the most favorable reaction will involve the addition of a nucleophile to form a vinyl halide intermediate. This alkene can now undergo a second protonation step, just like any other alkene, except that the carbocation will always be formed on the carbon bearing the halogen, since this carbocation is now stabilized by resonance with the halonium ion. The final result of the addition is that two moles of halogen halide are added, to give a 1,1-dihalide. Addition of Halogen to Alkynes The addition of halogen to alkynes is a stepwise process involving a "halonium" ion intermediate. The formation of this intermediate is initiated through attack of halogen on the alkyne -system, to form the cyclic halonium ion (i.e., bromonium or chloronium ion) and expel the halogen anion (i.e., bromide or chloride). This intermediate is highly electrophilic and reacts rapidly with the best nucleophile in the system; that is, the halide anion expelled in the previous step. Attack by halide generates a vinyl halide, which is an alkene and can undergo a second addition of halogen. The final product of the reaction is therefore a 1,1,2,2-tetrahalide
Addition of Water to Alkynes The mercury-catalyzed addition of water to alkynes is another example of a stepwise process which generally involves a solvent-equilibrated carbocation intermediate. The formation of this intermediate is initiated through a simple acid-base equilibrium in which the mercury ion interacts with the alkyne T-system, which is functioning as a Lewis base. The chelated I>-system rearranges to form an sp? sigma bond adjacent to an sp? carbocation center If the alkyne is unsymmetrical, two carbocations are possible and the addition will proceed to form the most stable carbocation. As before, secondary centers will be favored over primary, and overall addition of water will follow the order predicted by Markovnikov's Rule. Addition of water forms a viny I alcohol, which is termed an" enol". Enols are unstable compounds which rapidly interconvert with the corresponding carbonyl compound. Hence, the final product of the hydration reaction is the formation of an aldehyde or ketone, with the oxygen bonded to the carbon of the alkyne which would ultimately yield the most stable carbocation H H3O'IHg Markoymilkow an ena intermediate regiochemistry R-C=C-H- HH2o,y Hg SO4 w Hydroboration of Alkynes The reaction of BH, with an alkyne begins with the Lewis acid chelation of the alkyne T-system by the boron This complex then rearranges in a more-or-less concerted manner to produce the viny l borane The reaction seems to be dominated
Addition of Water to Alkynes The mercury-catalyzed addition of water to alkynes is another example of a stepwise process which generally involves a solvent-equilibrated carbocation intermediate. The formation of this intermediate is initiated through a simple acid-base equilibrium in which the mercury ion interacts with the alkyne -system, which is functioning as a Lewis base. The chelated >-system rearranges to form an sp2 sigma bond adjacent to an sp2 carbocation center. If the alkyne is unsymmetrical, two carbocations are possible and the addition will proceed to form the most stable carbocation. As before, secondary centers will be favored over primary, and overall addition of water will follow the order predicted by Markovnikov's Rule. Addition of water forms a vinyl alcohol, which is termed an "enol". Enols are unstable compounds which rapidly interconvert with the corresponding carbonyl compound. Hence, the final product of the hydration reaction is the formation of an aldehyde or ketone, with the oxygen bonded to the carbon of the alkyne which would ultimately yield the most stable carbocation. Hydroboration of Alkynes The reaction of BH3 with an alkyne begins with the Lewis acid chelation of the alkyne -system by the boron. This complex then rearranges in a more-or-less concerted manner to produce the vinyl borane. The reaction seems to be dominated
by steric effects and the boron attaches to the least hindered carbon. All three equivalents of the boron hydride can be utilized in separate reactions to give a triviny l borane. The organoborane which is formed can be oxidized by alkaline peroxide to form the alcohol by a mechanism which involves attack of peroxide anion on the boron, followed by alkyl migration to the oxygen, with loss of hydroxide anion. The resulting borate ester is rapidly hydrolyzed by the alkaline conditions to form an"". Rearrangement of the enol to the corresponding carbony l compound yields an aldehyde or ketone, with the oxygen bonded to the carbon of the alkyne which would generally yield the least stable carbocation (generally, antiMarkovnikov addition) H 2. H202, HoH- ape varkormikon regiochemistry Reduction of Alkynes Catalytic hydrogenation of alkynes with H, and a standard catalyst (Pt or Pd supported on charcoal, etc.) produces the corresponding alkane. However partial reduction of an alkyne to an alkene is possible using a poisoned catalyst", such as Pd or Pt on BaSO, or with the "Lindar Catalyst. In these reactions, addition of hydrogen is syn(cis) to yield the cis alkene. The transfer of hydrogen occurs in a strictly cis manner, probably due to the geometric constraints of the metal surface. The detailed mechanism is not trivial, and probably involves several metal-carbon bonded species. CH2cH3 H2, Pdrc CHCH3 HC=C-CH H,C-CHa-Ch ①- H,LIndar catalyst (also R or Pt/Basos Alkynes can also be partially reduced to trans-alkenes using a dissolving metal
by steric effects and the boron attaches to the least hindered carbon. All three equivalents of the boron hydride can be utilized in separate reactions to give a trivinyl borane. The organoborane which is formed can be oxidized by alkaline peroxide to form the alcohol by a mechanism which involves attack of peroxide anion on the boron, followed by alkyl migration to the oxygen, with loss of hydroxide anion. The resulting borate ester is rapidly hydrolyzed by the alkaline conditions to form an "enol". Rearrangement of the enol to the corresponding carbonyl compound yields an aldehyde or ketone, with the oxygen bonded to the carbon of the alkyne which would generally yield the least stable carbocation (generally, anti-Markovnikov addition). Reduction of Alkynes Catalytic hydrogenation of alkynes with H2 and a standard catalyst (Pt or Pd supported on charcoal, etc.) produces the corresponding alkane. However, partial reduction of an alkyne to an alkene is possible using a "poisoned catalyst", such as Pd or Pt on BaSO4, or with the "Lindar Catalyst". In these reactions, addition of hydrogen is syn (cis) to yield the cis alkene. The transfer of hydrogen occurs in a strictly cis manner, probably due to the geometric constraints of the metal surface. The detailed mechanism is not trivial, and probably involves several metal-carbon bonded species. Alkynes can also be partially reduced to trans-alkenes using a "dissolving metal