《有机化学：第七章-3 E2Reaction》由会员分享，可在线阅读，更多相关《有机化学：第七章-3 E2Reaction（44页珍藏版）》请在金锄头文库上搜索。
1、ReviewE2 Reaction：E2MechanismAlkyl Leaving Group BaseSolventstereochemistryOne step reaction with a transition state3RX 2RX 1RXRI RBr RCl RFHigher basicity of base is favorableHave some effectsanti- periplanar geometry(3) The E1 ReactionChemical Properties of Halogen-Substituted Hydrocarbons Just as
2、 the E2 Reaction is analogous to the SN2 reaction, there is a close analog to the SN1 reaction called the E1 reaction (for elimination, unimolecular).Relative reactivity: 3RX 2RX 1RXRI RBr RCl RFChemical Properties of Halogen-Substituted Hydrocarbonsno geometric requirement More stable productHChemi
3、cal Properties of Halogen-Substituted HydrocarbonsE1 : rearrangement of carbocationNaOHE1E2动力学动力学= kRX ( (一级反应一级反应) )= kRXB- ( (二级反应二级反应) )立体化学立体化学无立体选择性无立体选择性反式共平面消除反式共平面消除R-X的反应活性的反应活性3oRX 2oRX 1oRXRI RBr RCl RF3oRX 2oRX 1oRXRI RBr RCl RF碱碱影响不大影响不大强碱和浓碱有利强碱和浓碱有利溶剂的影响溶剂的影响极性溶剂对反应有利极性溶剂对反应有利有影响有影响重排
4、反应重排反应常见常见无无竞争反应竞争反应SN1SN2Chemical Properties of Halogen-Substituted HydrocarbonsChemical Properties of Halogen-Substituted HydrocarbonsChemical Properties of Halogen-Substituted Hydrocarbonsa. For primary alkyl halides: SN2 substitution occurs if a nucleophile such as RS-, I-, CN- and NH3 is used.
5、E2 elimination takes place if a strong, sterically, hindered base is used. Summary of Reactivity :SN1, SN2, E1, E2：Chemical Properties of Halogen-Substituted Hydrocarbonsb. For secondary alkyl halides:SN2 and E2 occur together, often leading to a mixture of products. If a weakly basic nucleophile is
6、 used in a polar aprotic solvent, SN2 predominates. If a strong base such as CH3CH2O-, OH-, or NH2- is used, E2 predominates. Chemical Properties of Halogen-Substituted Hydrocarbonsc. For tertiary alkyl halides: E2 occurs when a base such as OH-,or OR- is used. By contrast, reaction under neutral co
7、nditions leading to a mixture of products resulting from SN1 and E1.ababChemical Properties of Halogen-Substituted HydrocarbonsExercise：1. a bab2. Comparing the relatively reactivity of the following compounds in KOH-EtOH solution.Chemical Properties of Halogen-Substituted Hydrocarbons123Chemical Pr
8、operties of Halogen-Substituted Hydrocarbons3. Complete the following reactions:(1) (2) 4. Try to synthesis the following compound with inorganic compounds and organic raw materials (less than four carbon ).Chemical Properties of Halogen-Substituted HydrocarbonsChemical Properties of Halogen-Substit
9、uted HydrocarbonsOrganometallic Compound 有机金属化合物有机金属化合物4. Grignard ReagentsChemical Properties of Halogen-Substituted Hydrocarbons RX react with magnesium metal in dry ether or tetrahydrofuran (THF) solvent to yield organo-magnesium halides, RMgX. The products, called Grignard reagents after their d
10、iscoverer.P215-2161RX 2RX 3RXRI RBr RCl RFRelative reactivity: V. GrignardChemical Properties of Halogen-Substituted HydrocarbonsPhCH2X and CH2=CH-CH2X are so reactive :Coupling reaction偶联偶联(1) Low temperature(2) Dilute solutionare less reactive, the reaction should be occurred in those solvents wit
11、h high b.p. such as :, CH3O-CH2CH2OCH3THFChemical Properties of Halogen-Substituted HydrocarbonsThe reactions of ethylmagnesium bromide:Chemical Properties of Halogen-Substituted HydrocarbonsThe preparation of organo-magnesium halides(有机卤化镁有机卤化镁): 1)There must be no water, no air in the reaction sys
12、tem (无水，无氧无水，无氧).2)The substrate does not contain any active hydrogen(活性氢活性氢).3)The solvent also should contain no active hydrogen.5. Alkyllithium reagents (烷基锂烷基锂)Chemical Properties of Halogen-Substituted Hydrocarbons RLi can be prepared by the reaction of an alkyl halides with lithium metal. For
13、example:中文书中文书：P248-249 RLi is more active than RMgX One of the most valuable reactions of alkyllithiums is their use in making lithium diorganocopper compounds (二烷基铜锂二烷基铜锂)，R2CuLi, called Gilman reagents. For example:Chemical Properties of Halogen-Substituted Hydrocarbons Gilman reagents are useful
14、 because they undergo organometallic coupling reactions with alkyl halides to yield hydrocarbon product.Corey-House reactionChemical Properties of Halogen-Substituted HydrocarbonsChemical Properties of Halogen-Substituted HydrocarbonsGood methods for : 1) preparation of hydrocarbon. 2) carbon chain
15、growth. Chemical Properties of Halogen-Substituted HydrocarbonsExercise：6. Reactions of Allyl (烯丙基烯丙基) Halides and Benzyl (苄基苄基) HalidesChemical Properties of Halogen-Substituted Hydrocarbonsa. Substitution reaction 中文书中文书：P284-285Chemical Properties of Halogen-Substituted HydrocarbonsChemical Prope
16、rties of Halogen-Substituted HydrocarbonsPropose the mechanism of the following reaction:Exercise:Allylic rearrangement-烯丙基重排烯丙基重排Chemical Properties of Halogen-Substituted Hydrocarbonsb. Elimination reactionTo form most stable conjugated alkenes ( (共轭烯烃）共轭烯烃）Chemical Properties of Halogen-Substitut
17、ed Hydrocarbons6. Reactions of Vinyl (乙烯基乙烯基) Halides and Phenyl (苯基苯基) HalidesAryl halides that have electron-withdrawingsubstituents on the orth or para position can undergo nucleophilic aromatic substitution.中文书中文书：P275-283Chemical Properties of Halogen-Substituted Hydrocarbonsa. Substitution rea
18、ctionMechanism:Addition-eliminationreaction1) Reactivity: F Cl Br I2) NO2 on the orth or para position of X. Chemical Properties of Halogen-Substituted HydrocarbonsAniline 苯胺苯胺Mechanism:Elimination-additionbenzyne Chemical Properties of Halogen-Substituted Hydrocarbonsb. Elimination reactionc. React
19、ed with metalsChemical Properties of Halogen-Substituted HydrocarbonsCorey-House Reaction:Wurtz-Fitting Reaction:Attaching a long straight chain to the phenyl ring Ullmann Reaction: A method to prepare biphenyl compounds Chemical Properties of Halogen-Substituted HydrocarbonsChemical Properties of H
20、alogen-Substituted HydrocarbonsExercise:1. Complete the following reaction:Chemical Properties of Halogen-Substituted HydrocarbonsChemical Properties of Halogen-Substituted Hydrocarbons2. Order the following set of compounds with respect to hydrolysis reaction(水解反应水解反应)abaChemical Properties of Halo
21、gen-Substituted HydrocarbonsHomework for this chapter-2:Chemical Properties of Halogen-Substituted Hydrocarbons1.Read “Summary and Key Word” and “Summary of Reactions” of Alkyl Halides (p235-p236) carefully;2. Predict the products of the following reactions:(2) (1) 3. How to complete the following c
22、onversion? Chemical Properties of Halogen-Substituted Hydrocarbons(1)(2)4. What product would you expect from the reaction of 1-phenyl-2-butene with NBS? Explain. Chemical Properties of Halogen-Substituted Hydrocarbons5. Translate the following list into Chinese. A Summary of Substitution and Elimin
23、ation ReactionChemical Properties of Halogen-Substituted HydrocarbonsIntramolecular Nucleophilic Substitution Reaction Intramolecular SN2 reactionMechanism:分子内的分子内的 SN2 反应反应Intramolecular Nucleophilic Substitution Reaction MechanismNeighboring group participation 邻基参与邻基参与Intramolecular Nucleophilic Substitution Reaction InversionInversionNeighboring group participation: (1) increase the reaction rate (2) retention of configuration
