有机化学：第三章-1 (Unsaturated Hydrocarbons Alkenes and Alkynes

1、Chapter Three Unsaturated Hydrocarbons: Alkenes and AlkynesStructures of Alkenes and Alkynes.Chemical Properties of Alkenes.What are Alkenes ( 烯烃烯烃) and Alkynes (炔烃炔烃) Chemical Properties of Alkynes. Nomenclature of Alkenes and Alkynes.Cis-Trans Isomerism in Alkenes. Synthesis of Alkenes and Alkynes

2、.What are Alkenes and AlkynesAlkenes： are hydrocarbons that contain a carbon-carbon double bond (C=C).General formula: CnH2n, where n is an integer.Alkynes： are hydrocarbons that contain a carbon-carbon triple bond (CC).General formula: CnH2n-2, where n is an integer.烯烃烯烃炔烃炔烃Chapter Three Unsaturate

3、d Hydrocarbons: Alkenes and AlkynesStructures of Alkenes and Alkynes.Chemical Properties of Alkenes.What are Alkenes and Alkynes? Chemical Properties of Alkynes. Nomenclature of Alkenes and Alkynes.Cis-Trans Isomerism in Alkenes. Synthesis of Alkenes and Alkynes.Structures of Alkenes and Alkynes1. S

4、tructures of AlkenesCCHHHHa. Ethylene (乙烯乙烯) is planar (flat).b. Ethylene has bond angles of approximately 120o.Sp2 Hybridization (杂化杂化)A process for obtaining sp2-hybridized carbon atomsUnhybridized p orbitalsp2 hybrid orbitals2px2py2pz2s2px2py2pz2s激激发发2pyExciteP13 90Osp2sp2psp2sp2120O120O120Opsp2S

5、ide viewTop viewStructures of Alkenes and AlkynesThree equivalent sp2 hybrid orbitals (green) lie in a plane at angles of 120o to one other, and a single unhybridized p orbital (red) is perpendicular(垂直垂直) to the sp2 plane.HHHH sp2-hybridized orbitals: head on head to form C-CbondStructures of Alken

6、es and Alkynesunhybridized p orbitals: sideways overlapping to form bondAttention: Rotating one carbon of the double bond will break the pi () bond, for then the axes of the p orbitals are not parallel and there is less net overlap between them.Structures of Alkenes and Alkynes2. Structures of Alkyn

7、esa. Acetylene(乙炔乙炔) is linear.b. Acetylene has bond angles of approximately 180o.CCHH120pm106pm180oSp Hybridization (杂化杂化)A process for obtaining sp-hybridized carbon atomsExcite2px2py2pz2s2px2py2pz2s激激发发2py2pzunhybridized p orbitalssp hybrid orbitalsP16Structures of Alkenes and Alkynesthe two sp h

8、ybrid orbitals of carbon lie at an angle of 180o to each other along an axis perpendicular to the axes of the two unhybridized p orbitals. When two sp-hybridized carbons approach each other, one sp-sp bond and two p-p () bonds are formed.spsp2py2py2pz2pzThe character of bond :Can only exist with bon

9、d.Structures of Alkenes and AlkynesWeaker than bond. Cannot rotate.Chapter Three Unsaturated Hydrocarbons: Alkenes and AlkynesStructures of Alkenes and Alkynes.Chemical Properties of Alkenes.What are Alkenes and Alkynes? Chemical Properties of Alkynes. Nomenclature of Alkenes and Alkynes.Cis-Trans I

10、somerism in Alkenes. Synthesis of Alkenes and Alkynes.Cis-Trans Isomerism in AlkenesCCCH2CH3HHH3CCCCH2CH3HCH3Hb.p. 3.50.9 m.p.-139.5 -105.5 Cis-trans isomerism (顺反异构顺反异构)：The double bond can not rotatecis-trans-cis or trans ?The requirement for cis-trans isomerism in alkenes:Only when both double bo

11、nd carbons are bonded to two different groups.P79CCABDDCCBADDChapter Three Unsaturated Hydrocarbons: Alkenes and AlkynesStructures of Alkenes and Alkynes.Chemical Properties of Alkenes.What are Alkenes and Alkynes? Chemical Properties of Alkynes. Nomenclature of Alkenes and Alkynes.Cis-Trans Isomeri

12、sm in Alkenes. Synthesis of Alkenes and Alkynes.Prefix+Parent+SuffixNomenclature of Alkenes and Alkyneseneusing a series of rules similar to those for alkanesStep 1: Find the longest carbon chain containing the double bond, using the suffix ene . 1. Nomenclature of AlkenesP75Nomenclature of Alkenes

13、and AlkynesStep 2: Number the carbon atoms beginning at the end nearer the double bond (双键优先双键优先), if the double bond is equi- distant from the two ends, begin at the nearer the first branch.12345123456Step 3: Write the full name. Nomenclature of Alkenes and Alkynesb) Indicate the position of the do

14、uble bond by giving the number of the first alkene carbon and placing that number immediately before the parent name. a) Number the substituents according to their positions in the chain, and list them alphabetically.123451234563-Methyl-2-propyl-1-pentene3-Methyl-3-hexeneCCCH3CH2CH3CH2CH2HHNomenclat

15、ure of Alkenes and Alkynes123452-Ethyl-1-penteneCH3CH3a) The double bond is always between C1 and C2b) First substituent has as low a number as possible.123451,5-DimethylcyclopenteneCCH2CH3CH32-MethylpropeneIsobuteneNomenclature of Alkenes and AlkynesCH3CH=CHCH=CH21,3-PentadieneH2CCCHCH2CH32-Methyl-

16、1,3-butadieneNomenclature of Dienes (二烯烃二烯烃):Nomenclature of Alkenes and AlkynesNomenclature of Alkenes and AlkynesCCHH3CCH2CH3CH2CH2CH3Cis or trans isomer?E,Z system of nomenclature！Nomenclature of Alkenes and AlkynesSequence rules (次序规则次序规则)： assign priorities (先后次序先后次序) of the substituent groups

17、onthe double-bond carbons.Rule 1: Considering each of the double-bond carbons separately, identify the two atoms directly attached and rank them according to atomic number. An atom with higher atomic number receives higher priority than an atom with lower atomic number. (按原子序数分别比较大小，大者为按原子序数分别比较大小，大

18、者为“较优较优” 基团基团)= C: -I -Br -CI -F -OH -NH2 -CH3 -HP81Rule 2: If a decision cant be reached by ranking the first atoms in the substituent, look at the second, third, or fourth atoms away from the double-bond carbons until the first difference is found. (如果与双键碳原子直接相连的原子序数相同，则需要比较由该原子如果与双键碳原子直接相连的原子序数相同

19、，则需要比较由该原子外推至相邻的第二、第三个、第四等原子直至比较出较优基团为止外推至相邻的第二、第三个、第四等原子直至比较出较优基团为止)Nomenclature of Alkenes and AlkynesCHCH3=CCH3CH2CH3CH3=C=CC、C、HC、H、HH、H、HNomenclature of Alkenes and AlkynesRule 3: Multiple-bonded atoms are equivalent to the same number of single bonded atoms.(重键原子相当于相重键原子相当于相 同数目的单原子同数目的单原子)CHC

20、H2CCCHCC. C. HC. C. CHHNomenclature of Alkenes and Alkynes According to the sequence rules, assign priorities of the following group:Exercises:-N(CH3)2 -CONH2 -NO2 -CN1234CH2CH3CH=CH2CCHC(CH3)=CH2(C, H, H)(C, C, H)(C, C, C)(C, C, C)(C, C, C, H)(C, C, H, H)1234Nomenclature of Alkenes and AlkynesNomenclature of E, Z isomer of alkenen:E double bondHigher-priority groups are on the opposite sides.CCLowerHigherHigherLowerCCHigherLowerHigherLowerZ double bondHigher-priority groups are on the same side.Nomenclature of Alkenes and AlkynesCCCH2CH2CH3HH3CCH(CH3)2(Z)-3-Isopropyl-2-hexen