厦门大学化学化工学院：《有机化学》课程教学资源（授课教案）第五章 烯烃 Alkenes

第五章烯烃 H Alkenes CH H H H2C H 泌 H3C CH

第五章 烯 烃 Alkenes

Alkenes Q Alkenes are hydrocarbons that contain a carbon-carbon double bond functional group n The word olefin is often used as synonym in the chemical literature but alkene is the generally preferred term 已|■ Alkenes occur abundantly in nature,and many have important biological roles

Organic Chemistry Organic Chemistry Xiamen Xiamen University University A l kene s „ Alkenes are hydrocarbons that contain a carbon-carbon double bond functional group. „ The word olefin is often used as synonym in the chemical literature, but alkene is the generally preferred term. „ Alkenes occur abundantly in nature, and many have important biological roles

H H H 乙烯 α-蒎烯 Ethlyene a-Pinene ①D β-胡萝卜素 ⑨D β- Carotene

Organic Chemistry Organic Chemistry Xiamen Xiamen University University C C H H H H 乙烯 α−蒎烯 β−胡萝卜素 E thlyene α-Pinene β-Caro tene

51烯烃的结构 Structure of alkenes

Organic Chemistry Organic Chemistry Xiamen Xiamen University University 5.1 烯 烃的结构 Structure of Alkenes

烯烃的结构特征 Sp2杂化 兀键 ■C=c键长比C—C短 存在顺反异构

Organic Chemistry Organic Chemistry Xiamen Xiamen University University 烯烃的结构特征 „ sp 2杂化 „ π - 键 „ C=C键长比 C — C 短 „ 存在顺反异构

The carbon atoms in a double bond are sp hybridized and have three equivalent orbitals that lie in a plane at angles of 120 to one another 2p The fourth carbon orbital is an unhybridized p orbital which is perpendicular ①D to the sp plane sp2hybridized carbon

Organic Chemistry Organic Chemistry Xiamen Xiamen University University The carbon atoms in a double bond are sp2 hybridized and have three equivalent orbitals that lie in a plane at angles of 120 to one another. The fourth carbon orbital is an unhybridized p orbital , which is perpendicular to the sp2 plane

a' Antibonding orbital r. Antibonding orbital . C ①D a Bonding orbital m Bonding orbital a Both sigma and pi bonding molecular orbitals are filled. The antibonding combinations are unfilled

Organic Chemistry Organic Chemistry Xiamen Xiamen University University Both sigma and pi bonding molecular orbitals are filled. The antibonding combinations are unfilled

Carbon-carbon single bond: circular crOSs-section ①D Carbon-carbon double C bond; unsymmetrical crOSS-section ⑨D

Organic Chemistry Organic Chemistry Xiamen Xiamen University University

rotation Pi bond Broken pi bond after rotation (p orbitals are parallel) (p orbitals are perpendicular) ①D The pi bond must break in order for rotation to take place around a carbon- carbon double bond ⑨D

Organic Chemistry Organic Chemistry Xiamen Xiamen University University The pi bond must break in order for rotation to take place around a carbon-carbon double bond

π-键的键能 HH IIII H Q—8 键能C=C610.9kJ/mol c-c 3473k/ mol ①D 兀-键2636kJ/mol (乙烷单键旋转所需能量为12.1kJ/mo) ⑨D 般情况下双键不能自由旋转

Organic Chemistry Organic Chemistry Xiamen Xiamen University University π-键 的 键 能 C C H H H H C C C C 610.9 kJ / m o l 347.3 kJ / m o l 键能 π− 键 263.6 kJ / m o l (乙烷单键旋转所需能量为12.1 kJ/mol) 一般情况下双键不能自由旋转