有机化学双语版++Alkenes+2.ppt

1、Chapter 3 Alkenes,3.1 Alkene Nomenclature 3.2 Structure of Alkenes 3.3 Isomerism in Alkenes 3.3.1 Stereo-isomerism in Alkenes 3.3.2 Naming Stereoisomeric Alkenes 1. Naming by term Cis-trans 2. Naming by the E, Z Notational System,3.4 Reactions of Alkenes 3.4.1 Electrophilic Addition of Alkenes (1) A

2、ddition of Hydrogen Halides to Alkenes,Orientation of electrophilic addition Mechanism of the Reaction The stability of carbocations Carbocation Rearrangements Peroxide effect (2) Addition of Sulfuric acid to Alkenes (3) Acid-catalyzed Hydration of Alkenes (4) Hydroboration-Oxidation of alkenes (5)

3、Addition of Halogen to Alkenes,(6) Conversion of Alkenes to Vicinal Halohydrin 3.4.2 Hydrogenation ofAlkenes Heat of hydrogenation Stabilities of alkenes Mechanism of alkenes hydrogenation Stereochemistry of Alkenes hydrogenation Heterogeneous reaction 3.4.3 Oxidation of Alkenes (1) Epoxidation of A

4、lkenes (2) Hydroxylation of alkenes (3) Oxidative cleavage of alkenes: (A) Ozonolysis of Alkenes (B) With KMnO4 solution 3.4.4 Reaction of Alkenes with Alkenes: Polymerization,Alkenes: (Olefin),Hydrocarbon containing carbon-carbon double bond,The site of reactions,The functional group,（反应部位） （官能团）,A

5、liphatic hydrocarbons,Saturated (饱和烃),Unsaturated (不饱和烃),Alkanes cycloalkanes,Alkenes Alkynes,P76,Isobutylene （异丁烯）,- Pinene （ - 蒎烯）,3.1 Nomenclature of Alkenes,Terpene （萜烯）,IUPAC Names:,1. Give the base name by selecting the longest continuous carbon chain including the double bond .,-ene （某烯）,2. N

6、umber:,Give the boubly bonded carbons the lower number.,3. The location of substituents like alkanes.,4. When C number is over 10: 称某碳烯,5-Undecene,5-十一碳烯,2-Ethyl-1-pentene,4,4-Dimethylcycloheptene,Alkenyl groups（烯基）:,Vinyl （乙烯基）,Allyl (Allylic group) （烯丙基）,Propenyl（丙烯基）,Isopropenyl（异丙烯基）,Methenecycl

7、ohexane （亚甲基环己烷）,3.2 Structure of Alkenes,Structure of Ethylene:,sp2 Hybrid orbitals,P16, 1.9,C:,Ground state,Promotion of electron,Exited state,sp2-hybridized state,Hybri- dization,Three equivalent sp2 hybrid orbitals lie in a plane at angle of 120 to one another.,Geometric structure of C atom with

8、 sp2-hybrid: Planar triangle(平面三角),A single unhybridized p orbital perpendicular to the sp2 plane.,In the molecule of Ethylene :,The formation of C _ Cbond: sp2 _ sp2 overlap,The formation of C-C bond: 2p-2p side by side overlap.,The formation of C-H bond : sp2-1s overlap.,One C-C bond and 4 C-H bon

9、d are coplanar.,The formation of C-C bond: 2p-2p side by side overlap.,p orbital overlap,- bond,p orbital overlap,bond,bond,Carbon-carbon double bond,Models of Ethylene,3.3 Isomerism in Alkenes 3.3.1 Stereo-isomerism in Alkenes,P80, 3.3,Constitutional isomers,Stereoisomers,Cis-trans isomers,The diff

10、erent spacial arrangement of atoms or atomic groups.,cis-2-Butene,trans-2-Butene,Rotation about C-C double bond is restricted,Configuration,Physical properties: m.p; b.p,3.3.2 Naming Stereoisomeric Alkenes,1. Naming by term Cis-trans,The same atoms or atomic groups,on the same sides,on the opposite

11、sides,of the double bond.,2. Naming by the E, Z Notational system,To disubstituted Alkenes:,P83, 3.4,P175, Table 5.1,E, Z Notational system,base on an Sequence Rule （次序规则） Cahn-Ingold-Prelog priority Rule,Considering each of the double-bonded carbon, identify the two atoms directly attached and rank

12、 them according to atomic number.,Br Cl, C H,Low priority,High priority,E configuration: the high-priority groups are on the opposite sides of the double-bond,(E)-1-Bromo-1-chloro-1-butene (E)-1-氯-1-溴-1-丁烯,Low priority,High priority,Z configuration: the high-priority groups are on the same sides of

13、the double-bond,2. When two atoms directly attached to the double bond are identical, look at the second, third,or fourth atoms away from the double-bonded carbons until the first difference is found.,(Z)-3-methyl-2-hexene (Z)-3-甲基-2-己烯,3. Multiple-bonded atoms are equivalent to the same number of s

14、ingle-bonded atoms.,The carbon is bonde to H, O, O,The carbon is bonde to H, C, C,Organic Reactions:,The broken of original bonds, the formation of new bonds.,P88, 3.6,Reagent （试剂）,Product,Reactants,A covalent bond may break in two way:,Homolytic bond break(Radical) (均裂),Heterolytic bond break(Polar

15、) (异裂),CCl4,Reactional sites of alkene:,The bond is active and is readily attacked by the some reagents.,Addition reaction,- H is readily lost,3.4.1. Electrophilic Addition of Alkenes,（亲电加成反应）, electrons lie above and below the plane of double bond, so- bonded electrons are exposed (裸露).,- bond,The

16、bond is attacked by electron-seeking reagentsElectrophile （亲电试剂）,(1) Addition of Hydrogen Halides (卤化氢) to Alkenes,Alkane halide,P 109,4.1,Orientation of electrophilic addition: Markovnikovs Rule,Addition to an unsymmetrically substituted alkenes:,Markovnikovs Rule: In the addition of HX to an alken

17、e, the H attaches to the carbon with fewer alkyl groups and X attaches to the carbon with more alkyl groups.,Vladimir Vassilyevich Markovnikov,1838-1904,Mechanism of the Reaction:,Step 1.,The formation of the carbocation (正碳离子),Reactive intermediate,Step 2.,The formation of the carbocation is the ra

18、te-determining step.,P92, 3.8,The stability of carbocations:,P112, 4.3,The one raison that stabilize a carbocation: the electron-donating effect of alkyl groups.,The structure of carbocations:,The positively charge carbon atom is sp2-hybridized,The p orbital is vacant.,The carbocation is trigonal pl

19、ane.,Tertiary(3 ) Secondary(2 ) primary(1 ) Methyl,Regioselectivity (区域选择 性) of the reaction,P110, 4.2 Ch.59,The reaction that can proceed in more than one direction, but actually in which one direction is preferred.,Regiospecific (区域专一的),A more highly substituted carbocation is more stable than a l

20、ess highly substituted one.,The electron-donating or electron- withdraw effect of a group that is transmitted through bond.,Inductive effect(诱导效应) of substituents:,P22, Ch.9,Explanation for “Markovnikovs rule”,The stabilities of carbocation:,(I) (II),Electrophilic addition to an unsymmetri- cally su

21、bstituted alkene give the more highly substituted carbocation.,Carbocation Rearrangements (重排),Ch.60, 倒7,(40%) (60%),HCl,Cl-,(I),(II),Cl-,Stabilities of C+: Tertiary Secondary,Hydride-shift,0,Reactivity:,HI HBr HCl HF,Alkenes?,Peroxide effect (过氧化物效应),An unsymmetric alkene reacts with HBr in the pre

22、sent of a peroxide (R-O-O-R), the Anti-Markovnikov addition occurs.,Ch.61,(d),Free-redical addition,（过氧化乙酰） （过氧化苯甲 酰）,(2) Addition of Sulfuric acid to Alkenes,Ch. 63, (丙),Cold Concentrated H2SO4,Alkyl hydrogen Sulfate(硫酸氢酯),Hydrolysis(水解作用): A bond is cleaved by reaction with water.,Mono-substituted

23、 and Disubstituted alkenes:,Hydration (水合反应),Ok!,(3) Acid-catalyzed Hydration of Alkenes,P114, 4.4,(酸催化的烯烃水合反应),(4) Hydroboration-Oxidation(硼氢化-氧化) of alkenes,The method for preparation of the alcohols from anti-Markov. Adddition.,The hydroxyl group was added on less substituted carbon.,Organoborane

24、s (有机硼烷),Major method to prepare alcohols in industry,Catalyst: Dilute H2SO4, H3PO4,Ch.66,He discovered the hydroboration reaction (addition of diborane to alkenes) and developed the multi- faceted and synthetically useful chemistry of the resulting organo- boranes. In this photo, Professor Brown ho

25、lds a model of 9 -borabicyclo3.3.1nonane (9-BBN), prepared by adding borane to 1,5-cyclooctadiene and itself a stable, useful hydroborating reagent. This work is summarized in Browns book Organic Synthesis via Boranes (1975). Brown contri- buted to many other areas of organic chemistry, among which

26、were selective reducing agents, steric effects (in displacement, elimination and acid-base reactions), and directive effects in electrophilic aromatic substitution (the + constant).,Brown is perhaps the most prolific organic chemist of the 20th century. He is best known for his work in organoboron c

27、hemistry, for which he shared (with G. Wittig) the 1979 Nobel Prize in Chemistry.,Hydroboration :,Electronegativity: H 2.1, B 2.0,organoborane,Reagent: boron hydride,B2H6,THF (四氢呋喃),Solvents ether: Et2O,Diglyme: CH3OCH2CH2OCH2CH2OCH3,（二甘醇二甲 醚）,borane,Oxidation:,Hydrogen peroxide,Feature of the react

28、ion:,Equal to the anti-Markov. Addition of H2O to alkenes,1. Regioselectivity: following Markov. Rule.,2. Stereochemistry:,Syn-addition （顺式加成） :,Two atoms or groups add to the same face of a double bond.,trans-2-Methylcyclo- pentanol,3. Non rearrangement,Syn-addition,Anti-addition （反式加成） : Two atoms

29、 or groups add to the opposite faces of a double bond.,The stereoselectivity of Hydroboration- Oxidation:,Problem: What products would you obtain from reaction of 1-ethylcyclopentenewith BH3,followed by H2O2,OH-?,(5) Addition of Halogen to Alkenes,P116, 4.5,0,Vicinal dihalide (邻二卤代物),Solvents: CH2Cl

30、2,CHCl3, Acetic acid,Identification for C=C.,Reagents: Cl2, Br2.,Mechanism of the reaction:,Step1.,Step2.,Bromo-anion attacks from side opposite.,Step 1 is the rate- determining step.,Bromonium ion ( 型离子),Step 1.,Step 2.,Stereochemistry of halogen addition,Anti-addition,(6) Conversion of Alkenes to

31、Vicinal Halohydrin(邻卤代醇),- Halohydrin,Ch.63,(丁),Addition of halogen in aqueous solution.,Mechanism of the reaction:,Features of the reaction:,Following Markov. Rule, equal to the addition of one mole of HO-Cl+(次氯酸),2. Anti-addition,3.4.2 Hydrogenation of Alkenes,P118,4.6,+ heat,Catalyst: Pt,Pd, Ni,F

32、eatures of the reaction:,1. An exothermic reaction,Broken:,bond, H-H bond,Formation: 2 C-H bond,Heat of hydrogenation:,The heat evolved on hydrogenation of one mole. of an alkene.,The higher is the heat of hydrogenation, the less stable is the alkene.,The heat of hydrogenation is relative to the sta

33、bility of alkenes.,Stability of alkenes:,Cis- Trans-,Ch.54,(乙),Mechanism of alkene hydrogenation,2. The role of the metal catalyst,Very slowly without catalyst.,Changing the reaction path to lower activation energy （活化能）.,The addition of hydrogen to alkene is catalytic hydrogenation （催化氢化）.,3. Stere

34、ochemistry of Alkene hydrogenation,Alkene hydrogenation: syn-addition,Mechanism of alkene hydrogenation,4. Heterogeneous reaction （异相反 应）,Solvent （溶剂）： ethanol, hexane or acetic acid.,To dissolve a alkene,Metal: solid,The reaction occurs at the interface of two phase.,Homogeneous(均相）,3.4.3 Oxidation

35、 of Alkenes,(1) Epoxidation of Alkenes (环氧化反应),P238, 6.18,Peroxy acid (过氧酸),Epoxide (环氧化物),Shapless, K. B. got the 2001 Nobel prize.,Solvents: acetic acid, CH2Cl2, CHCl3,Reagent:,Peroxyacetic acid (过氧乙酸),Preparation of epoxides from alkenes,K. Barry Sharpless, Ph.D. Organic/Inorganic ChemistThe Scri

36、pps Research Institute/chem/sharpless/cv.html,(2) Hydroxylation(羟基化反应) of alkenes:,Alkenes react with potassium perman- ganate or Osmium tetraoxide in basic solution to form 1,2-diols (glycol)(二醇).,syn stereochemistry.,Cold solution of NaOH,NaHSO3,P120,4.7,Mechanism of the reaction:,(3) Oxidative cleavage of alkenes:,(A) Ozonolysis of Alkenes (臭氧化反应),Ch.70,O3(ozone),Ozonide,Reducing agent: Zn,Hydrolysi