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) Addition of Hydrogen Halides to Alkenes

2. 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) Addition of Halogen to Alkenes

3. (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 Alkenes (2) Hydroxylation of alkenes (3) Oxidative cleavage of alkenes: (A) Ozonolysis of Alkenes (B) With KMnO 4 solution 3.4.4 Reaction of Alkenes with Alkenes: Polymerization

4. Alkenes: (Olefin) Hydrocarbon containing carbon-carbon double bond The site of reactionsThe functional group （反应部位） （官能团） Aliphatic hydrocarbons Saturated ( 饱和烃 ) Unsaturated ( 不饱和烃 ) Alkanes cycloalkanes Alkenes Alkynes P76

5. Isobutylene （异丁烯） α- Pinene （ α- 蒎烯） Farnesene （法呢烯） 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）

6. 2. Number: 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

7. Alkenyl groups （烯基） : Vinyl （乙烯基） Allyl (Allylic group) （烯丙基） Propenyl （丙烯基） Isopropenyl （异丙烯基） Methenecyclohexane （亚甲基环己烷）

8. 3.2 Structure of Alkenes Structure of Ethylene: sp 2 Hybrid orbitals P16, 1.9 C: Ground state 2p2p 2s2s 1s1s Promotion of electron Promotion of electron Exited state 2p2p 2s2s 1s1s sp 2 -hybridized state 1s1s 2p2p sp 2 Hybri- dization Hybri- dization An sp 2 orbital 1/3 s orbital 2/3 p orbital

9. Three equivalent sp 2 hybrid orbitals lie in a plane at angle of 120° to one another. Geometric structure of C atom with sp 2 -hybrid: Planar triangle ( 平面三角 ) A single unhybridized p orbital perpendicular to the sp 2 plane. In the molecule of Ethylene : The formation of C _ Cσbond: sp 2 _ sp 2 overlap

10. The formation of C-C πbond: 2p-2p side by side overlap. The formation of C-H σbond : sp 2 -1s overlap. One C-C σbond and 4 C-H σbond are coplanar. The formation of C-C πbond: 2p-2p side by side overlap.

11. p orbital overlap H H H H σ- bond p orbital overlap

12. C C σbond πbond Carbon-carbon double bond

13. Models of Ethylene

14. 3.3 Isomerism in Alkenes 3.3.1 Stereo-isomerism in Alkenes P80, 3.3 1-Butene 2-Methyl-2- butene Isobutene cis-2-Butenetrans-2-Butene Constitutional isomers Constitutional isomers (I) (III)(IV)(II) (I)(II)(III)(IV) Stereoisomers (III) (IV) Cis-trans isomers

15. The different 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

16. 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 sides of the double bond. Prefix cis- trans - 2. Naming by the E, Z Notational system To disubstituted Alkenes: P83, 3.4

17. P175, Table 5.1 P175, Table 5.1 E, Z Notational system base on an Sequence Rule （次序规则） － Cahn-Ingold-Prelog priority Rule 1.Considering each of the double-bonded carbon, identify the two atoms directly attached and rank 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 (E)-1-Bromo-1-chloro-1-butene (E)-1- 氯 -1- 溴 -1- 丁烯 Low priority High priority

18. Z configuration: the high-priority groups are on the same sides of 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 (Z)-3-methyl-2-hexene (Z)-3- 甲基 -2- 己烯

19. <> < 3. Multiple-bonded atoms are equivalent to the same number of single-bonded atoms. The carbon is bonde to H, O, O The carbon is bonde to H, C, C

20. Organic Reactions: The broken of original bonds, the formation of new bonds. The broken of original bonds, the formation of new bonds. P88, 3.6 Starting material （原料） Substrate （底物） Reagent （试剂） Reagent （试剂） Product Reactants A covalent bond may break in two way: Homolytic bond break(Radical) ( 均裂 ) Homolytic bond break(Radical) ( 均裂 ) Heterolytic bond break(Polar) ( 异裂 ) Heterolytic bond break(Polar) ( 异裂 ) CCl 4 solvent

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

22. The πbond is attacked by electron-seeking reagents － Electrophile （亲电试剂） An reaction rule: Electronegative species + Electropositive species (1) Addition of Hydrogen Halides ( 卤化氢 ) to Alkenes 2-Butene2-Chlorobutane Alkane halide Alkane halide P 109,4.1

23. Orientation of electrophilic addition: Markovnikov’s Rule Addition to an unsymmetrically substituted alkenes: Markovnikov’s Rule: In the addition of HX to an alkene, the H attaches to the carbon with fewer alkyl groups and X attaches to the carbon with more alkyl groups. (80%) (20%) Vladimir Vassilyevich Markovnikov 1838-1904

24. Mechanism of the Reaction: Step 1. The formation of the carbocation ( 正碳离子 ) Reactive intermediate Reactive intermediate Step 2. The formation of the carbocation is the rate-determining step. P92, 3.8 slow fast

25. 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: + 120° The positively charge carbon atom is sp 2 -hybridized, The p orbital is vacant. The carbocation is trigonal plane. Tertiary(3 ) > Secondary(2 ) > primary(1 ) > Methyl

26. Regioselectivity ( 区域选择 性 ) of the reaction P110, 4.2 Ch.59 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 less highly substituted one. + δ + δ + The electron-donating or electron- withdraw effect of a group that is transmitted through σbond. Inductive effect ( 诱导效应 ) of substituents: P22, Ch.9 P22, Ch.9

27. Explanation for “Markovnikov’s rule” (I) (II) The stabilities of carbocation: (I) > (II) Electrophilic addition to an unsymmetri- cally substituted alkene give the more highly substituted carbocation. Electrophilic addition to an unsymmetri- cally substituted alkene give the more highly substituted carbocation.

28. Carbocation Rearrangements ( 重排 ) Ch.60, 倒 7 Ch.60, 倒 7 (40%) (60%) HCl Cl - (I) (II) Cl - Stabilities of C +: Tertiary > Secondary Stabilities of C +: Tertiary > Secondary Hydride-shift 0℃0℃ Problem: Propose a mechanism to account for the following result:

29. Reactivity: HI > HBr > HCl >> HF Based on the ability to proton-donating of HX Alkenes? Peroxide effect ( 过氧化物效应 ) An unsymmetric alkene reacts with HBr in the present of a peroxide (R-O-O-R), the Anti-Markovnikov addition occurs. Ch.61,(d) Free-redical addition Free-redical addition （过氧化乙酰） （过氧化苯甲 酰）

30. (2) Addition of Sulfuric acid to Alkenes Ch. 63, ( 丙 ) Cold Concentrated H 2 SO 4 Cold Concentrated H 2 SO 4 Alkyl hydrogen Sulfate( 硫酸氢酯 ) Hydrolysis ( 水解作用 ) : A bond is cleaved by reaction with water. Hydrolysis ( 水解作用 ) : A bond is cleaved by reaction with water. Mono-substituted and Disubstituted alkenes: Hydration ( 水合反应 ) Ok!

31. (3) Acid-catalyzed Hydration of Alkenes P114, 4.4 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 method for preparation of the alcohols from anti-Markov. Adddition. The hydroxyl group was added on less substituted carbon. Organoboranes ( 有机硼烷 ) Herbert Charles Brown Got the 1979 Nobel prize Major method to prepare alcohols in industry Catalyst: Dilute H 2 SO 4, H 3 PO 4 Catalyst: Dilute H 2 SO 4, H 3 PO 4 Ch.66,

32. 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 holds a model of 9 -borabicyclo[3.3.1]nonane (9-BBN), prepared by adding borane to 1,5-cyclooctadiene and itself a stable, useful hydroborating reagent. This work is summarized in Brown's book "Organic Synthesis via Boranes" (1975). Brown contri- buted to many other areas of organic chemistry, among which were selective reducing agents, steric effects (in displacement, elimination and acid-base reactions), and directive effects in electrophilic aromatic substitution (the σ+ constant). Brown is perhaps the most prolific organic chemist of the 20th century. He is best known for his work in organoboron chemistry, for which he shared (with G. Wittig) the 1979 Nobel Prize in Chemistry. Brown is perhaps the most prolific organic chemist of the 20th century. He is best known for his work in organoboron chemistry, for which he shared (with G. Wittig) the 1979 Nobel Prize in Chemistry.

33. Hydroboration : Electronegativity: H 2.1, B 2.0 Electronegativity: H 2.1, B 2.0 organoborane Reagent: boron hydride B2H6B2H6 THF ( 四氢呋喃 ) Solvents ether: Et 2 O, Diglyme: CH 3 OCH 2 CH 2 OCH 2 CH 2 OCH 3 （二甘醇二甲 醚） borane

34. Oxidation: Hydrogen peroxide Feature of the reaction: Equal to the anti-Markov. Addition of H 2 O 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.

35. trans-2-Methylcyclo- pentanol 3. Non rearrangement Syn-addition Anti-addition （反式加成） : Two atoms 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 BH 3,followed by H 2 O 2,OH - ? Problem: What products would you obtain from reaction of 1-ethylcyclopentenewith BH 3,followed by H 2 O 2,OH - ?

36. (5) Addition of Halogen to Alkenes P116, 4.5 P116, 4.5 0℃0℃ Vicinal dihalide ( 邻二卤代物 ) Solvents: CH 2 Cl 2,CHCl 3, Acetic acid Identification for C=C. Reagents: Cl 2, Br 2. Mechanism of the reaction: Step1. Step2. Bromo-anion attacks from side opposite. Step 1 is the rate- determining step. Bromonium ion ( 型离子 )

37. Step 1.

38. Step 2.

39. Stereochemistry of halogen addition Anti-addition (6) Conversion of Alkenes to Vicinal Halohydrin ( 邻卤代醇 ) β- Halohydrin Ch.63,( 丁 ) Addition of halogen in aqueous solution. Addition of halogen in aqueous solution.

40. Mechanism of the reaction: Features of the reaction: 1.Following Markov. Rule, equal to the addition of one mole of HO - Cl + ( 次氯酸 ) 2. Anti-addition

41. 3.4.2 Hydrogenation of Alkenes P118,4.6 + heat Catalyst: Pt,Pd, Ni Features of the reaction: 1. An exothermic reaction Broken:πbond, H-H σbond Formation: 2 C-H σbond Heat of hydrogenation: The heat evolved on hydrogenation of one mole. of an alkene.

42. The higher is the heat of hydrogenation, the less stable is the alkene. The heat of hydrogenation is relative to the stability of alkenes. Stability of alkenes: Cis- < Trans- Ch.54,( 乙 )

43. 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. Stereochemistry of Alkene hydrogenation Alkene hydrogenation: syn-addition

44. Catalyst Hydrogen absorbed on catalyst surface Hydrogen absorbed on catalyst surface Complex of alkene to catalyst Complex of alkene to catalyst Mechanism of alkene hydrogenation Insertion of hydrogen into C=C Insertion of hydrogen into C=C Alkane product Alkane product Regenerated catalyst Regenerated catalyst H2H2 HH HH H H +

45. 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）

46. 3.4.3 Oxidation 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, CH 2 Cl 2, CHCl 3 Reagent: Peroxyacetic acid ( 过氧乙酸 ) Preparation of epoxides from alkenes

47. K. Barry Sharpless, Ph.D. Organic/Inorganic Chemist The Scripps Research Institute http://www.scripps.edu/chem/sharpless/cv.html

48. (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 ). Cyclohexene cis-cyclohexanediol (37%) syn stereochemistry. Cold solution of NaOH NaHSO 3 P120,4.7

49. Mechanism of the reaction: (3) Oxidative cleavage of alkenes: (A) Ozonolysis of Alkenes ( 臭氧化反应 ) Ch.70 O 3 (ozone) Ozonide Reducing agent: Zn HydrolysisAldehydes or ketones

50. Identification to the structure of a allkene Ex. 2-Methyl-2-butene Acetone Acetaldehyde (B) With KMnO 4 solution In hot OH - solution, neutral or acidic solution: Isopropylidene- cyclohexene ( 异亚丙基环己烯 ) Cyclohexa- none ( 环己酮 ) Acetone

51. 3.4.5 Reaction of Alkenes with Alkenes: Polymerization Polyethylene ( 聚乙烯 ) Ethylene: monomers Polyethylene: polymer Polymerization: many individual alkene molecules combine to give a high-molecular-weight product. Polymerization: many individual alkene molecules combine to give a high-molecular-weight product. Ziegler – Natta catalyst Received the 1963 Nobel Prize Received the 1963 Nobel Prize

52. b. 1903 d. 1979 "for their discoveries in the field of the chemistry and technology of high polymers" Karl Ziegler Giulio Natta 1/2 of the prize Federal Republic of Germany Italy Institute of Technology Milan, Italy Max-Planck-Institut for Kohlenforschung (Max-Planck-Institue for Carbon Research) M 黮 heim/Ruhr, Federal Republic of Germany b. 1898 d. 1973 The Nobel Prize in Chemistry 1963 http://www.nobel.se/chemistry/laureates/1963/index.html

53. Problems to Chapter 3: P103: 3.27(a): (b) 3.28 (b) 3.29 (e), (f) 3.30 (a) 3.32 3.33(b) 3.35 3.39(b) 3.41 3.42(c) 4.34 4.37(c), (e)(1)BH 3,(2)H 2 O 2,OH － 4.39 4.40(a),(c) Show the reac- tions. 4.45(a), (b), (d) (e) 4.50* 4.57 4.34 4.37(c), (e)(1)BH 3,(2)H 2 O 2,OH － 4.39 4.40(a),(c) Show the reac- tions. 4.45(a), (b), (d) (e) 4.50* 4.57

54. Additional problems: 1.Vinylcyclopropane reacts with HBr to yield a rearranged alkyl bromide.Follow the flow of electrons as represented by the curve arrows, show the structure of the intermediate in brackets, and show the structure of the final product. 2. Predict the products of the following reactions. Don’t worry about the size of the molecule, concentrate on the functional groups. Cholesterol ( 胆固醇 )

55. A look ahead: Problems to Chapter 4. Alkyne P146. 4.25(b) 4.26(b),(c) 4.29(c) 4.41 Show the reactions. 4.42 4.44 4.45(c) 4.48 4.52 4.56 A look ahead: Problems to Chapter 4. Alkyne P146. 4.25(b) 4.26(b),(c) 4.29(c) 4.41 Show the reactions. 4.42 4.44 4.45(c) 4.48 4.52 4.56