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,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,(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 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）,Aliphatic 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. 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,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）,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 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 bond 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 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,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.,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 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 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 single-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) (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 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 alkene, the H attaches to the carbon with fewer alkyl groups and X attaches to the carbon