isomerism e Conformational isomers they can be interconverted by rotation about one or more sigma-bonds the interconversion are so rapid that we cannot separate them Staggered Eclipsed H H H H H H H H H H Newman projection sawhorse projection Newman projection sawhorse projection
Isomerism Conformational isomers ---- they can be interconverted by rotation about one or more sigma-bonds ---- the interconversion are so rapid that we cannot separate them H H H H H H H H H H H H Staggered Newman projection sawhorse projection 600 H H H H H H H H H H H H Eclipsed 0 0 Newman projection sawhorse projection
烷烃和环烷烃的构象异构 ●1. Ethane Staggered Eclipsed H H 60 H H H H H H Newman projection sawhorse proje ction Newman projection sawhorse projection Conformational analysis .--describes the energetic of such conformational interconversion
一、烷烃和环烷烃的构象异构 1.Ethane Conformational analysis ---- describes the energetic of such conformational interconversion H H H H H H H H H H H H Staggered Newman projection sawhorse projection 600 H H H H H H H H H H H H Eclipsed 0 0 Newman projection sawhorse projection
烷烃和环烷烃的构象异构 2 Butane H3C CH H3c H H CH H D syn eclipsed gauche conformer anti conforme yn eclipsed Steric Strain aa steric effect e van der Waals repulsion of groups that are close to each other
一、烷烃和环烷烃的构象异构 2. Butane Steric Strain ---- a steric effect van der Waals repulsion of groups that are close to each other H H CH3 H3C H H C H H3C H H3C H H C' H3C H H H3C H H B' H3C H H H H CH3 A syn eclipsed H H CH3 H3C H H B gauche conformer H CH3 H H3C H H D anti conformer H3C H H H H CH3 A syn eclipsed
烷烃和环烷烃的构象异构 思考题: 已知乙烷中重叠式与叉式的能量差为 121KJmo,丁烷中邻位交叉、部分重 叠、全重叠与对位交叉构象的能量差分 别为38、14.6、226KJ/mol,请以乙 烷的交叉式能量设为零来计算HH cH3CH3、CH3H重叠和cH3CH3邻位 交叉的能量
一、烷烃和环烷烃的构象异构 思考题： 已知乙烷中重叠式与交叉式的能量差为 12.1 KJ/mol，丁烷中邻位交叉、部分重 叠、全重叠与对位交叉构象的能量差分 别为3.8、14.6、22.6 KJ/mol，请以乙 烷的交叉式能量设为零来计算H-H 、 CH3 -CH3 、CH3 -H重叠和CH3 -CH3邻位 交叉的能量
HH重叠4KJ/mo CH2CH3重叠146 KJ/mol ●CH3H重叠53 KJ/mol ●CH2CH23邻位交叉38KJ/mol
H-H 重叠 4 KJ/mol CH3 -CH3 重叠 14.6 KJ/mol CH3 -H 重叠 5.3 KJ/mol CH3 -CH3 邻位交叉 3.8 KJ/mol