第六章常见反应机理优秀PPT.ppt

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1、第六章常见反应机理第一页，本课件共有51页Step 1:Chain initiation:formation of radicals from nonradical speciesStep 2:Step 3:Chain propagation:reaction of radicals and a molecules to form a new radical1.1 Alkane halogenation reaction1.A Radical Chain Mechanism第二页，本课件共有51页Chain termination(Destruction of radicals):Dispro

2、portionationCoupling第三页，本课件共有51页Bond dissociation energy(kJ/mol)第四页，本课件共有51页Enthalpy change H?Entropy change S?Free energy change G?第五页，本课件共有51页How about the chlorination of methane?How about the bromination of propene?Activity:FClBrI;Allyl,3 2 1Selectivity:FClBr 2 1第六页，本课件共有51页1.2 Radial Oxidation

3、with Oxygen Chain initiationChain propagation第七页，本课件共有51页Draw a mechanism for the following reaction第八页，本课件共有51页1.3.Radical addition reactionInitiationPropagationH-O 428H-Cl 432H-Br 368C-Br 272,H-Cl 432,H-C 403,pi键键682368第九页，本课件共有51页2.Electrophilic addition to C,C multiple bonds2.1.Carbocation mecha

4、nismDirection:The more stable carbocation form preferentially Caution:Carbocation rearrangement!第十页，本课件共有51页第十一页，本课件共有51页2.2.Nium reaction mechanismminor contributing structureSterospecificity:Anti addition第十二页，本课件共有51页The electronegativity tell you which one is E+.第十三页，本课件共有51页2.3.Oxymercuration-Re

5、duction第十四页，本课件共有51页A bridged mercurinium:three-center/two-electron bond第十五页，本课件共有51页3.Nucleophilic addition to C,C multiple bonds第十六页，本课件共有51页4.Concerted addition to C,C multiple bondsA syn addition mechanism4.1.Catalytic hydrogenation第十七页，本课件共有51页4.2.Hydroboration-Oxidation第十八页，本课件共有51页第十九页，本课件共有5

6、1页4.3.OsO4-OxidationCatalytic amount OsO4(expensive and highly toxic)with peroxide第二十页，本课件共有51页4.4.KMnO4-Oxidation第二十一页，本课件共有51页4.5.Diels-Alder reaction第二十二页，本课件共有51页Overlap between the highest occupied MO of the diene(HOMO)and the lowest unoccupied MO of the dienophile(LUMO)is thermally allowed in

7、the Diels Alder Reaction,provided the orbitals are of similar energy.The reaction is facilitated by electron-withdrawing groups on the dienophile,since this will lower the energy of the LUMO.第二十三页，本课件共有51页 There are“inverse demand”Diels Alder Reactions that involve the overlap of the HOMO of the die

8、nophile with the LUMO of the diene.This alternative scenario for the reaction is favored by electron-donating groups on the dienophile and an electron-poor diene.第二十四页，本课件共有51页The endo product is usually favored by kinetic control due to secondary orbital interactions.第二十五页，本课件共有51页The reaction is d

9、iastereoselective.第二十六页，本课件共有51页5.Substitution Reactions5.1 Nuclephilic Substitution ReactionsSN1SN2第二十七页，本课件共有51页SN1SN2Tertiary alkyl Primary alkylPoor nucleophile Good nucleophilePolar solvent Nonpolar solventGood Leaving group Poor leaving group第二十八页，本课件共有51页5.2 Electrophilic Aromatic Substitutio

10、n Reactions第二十九页，本课件共有51页5.3 Nucleophilic Aromatic Substitution ReactionsR=group with both-I and-C effects第三十页，本课件共有51页6.Elimination reactionsE1E2E1cbSaytzeff ruleHofmann rule第三十一页，本课件共有51页Hofmann rule第三十二页，本课件共有51页-branches results in Hofmann product第三十三页，本课件共有51页第三十四页，本课件共有51页7.Name Reactions7.1.A

11、ldol condensation第三十五页，本课件共有51页7.2.Arndt-Eistert Synthesis-Wolff rearrangement 第三十六页，本课件共有51页7.3.Benzoin Condensation第三十七页，本课件共有51页X.Linghu,J.S.Johnson,Angew.Chem.,2003,115,2638Key Intermediate:第三十八页，本课件共有51页7.4.Claisen Condensation Key Intermediate:第三十九页，本课件共有51页Dieckmann Condensation第四十页，本课件共有51页7

12、.5.Cannizzaro Reaction第四十一页，本课件共有51页7.6.Diazotisation第四十二页，本课件共有51页7.7.Haloform Reaction 第四十三页，本课件共有51页7.8.Hell-Volhard-Zelinsky Reaction第四十四页，本课件共有51页第四十五页，本课件共有51页7.9.Mannich Reaction第四十六页，本课件共有51页7.10.Michael Additiondonors acceptors 第四十七页，本课件共有51页7.11.Arbuzov ReactionMichaelis-Arbuzov Reaction第四十八页，本课件共有51页7.12.Reformatsky Reaction第四十九页，本课件共有51页7.13.Wolff-Kishner Reduction第五十页，本课件共有51页第五十一页，本课件共有51页