ORGANIC CHEMISTRY Chapter 4 4.8 Sigma Bonds and bond Rotation Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 4 4.8 Sigma Bonds and Bond Rotation
ORGANIC CHEMISTRY Chapter 4 o The different arrangements of atoms caused b rotation about a single bond are called conformations A s of the molecule, and a specific conformation is called a conformer(构象异构体, conformation Isomer) o an analysis of the energy changes that a molecule undergoes as groups rotate about single bonds Is called a conformational analysis(构象分析 o Unlike constitutional isomers, though, different conformers can't usually be isolated because they interconvert too rapidly Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 4 The different arrangements of atoms caused by rotation about a single bond are called conformations (构象)of the molecule, and a specific conformation is called a conformer (构象异构体, conformation isomer). An analysis of the energy changes that a molecule undergoes as groups rotate about single bonds is called a conformational analysis (构象分析). Unlike constitutional isomers, though, different conformers can’t usually be isolated because they interconvert too rapidly
ORGANIC CHEMISTRY Chapter 4 Conformations of ethane Representations of conformers o Newman projections( Newman投影式) Sawhorse(锯架式) o Wedge-dash(虚线楔线式,伞式) H H H、 H H H H H H H H H H H Newman projections Sawhorse Wedge-dash Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 4 Conformations of Ethane Representations of conformers Newman projections (Newman 投影式) Sawhorse (锯架式) Wedge-dash (虚线-楔线式 伞式) H H H H H H H H H H H H H H H H H H Newman projections Sawhorse Wedge-dash
ORGANIC CHEMISTRY Chapter 4 The staggered Conformation and the eclipsed Conformation(交叉式构象与重叠式构象) H 60 H H H H H H 重叠式构象个 交叉式构象 E closed Staggered The least stable conformation The most stabl conformation Torsional barrier(转动能垒)12.1kJmo1 Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 4 The Staggered Conformation and the Eclipsed Conformation (交叉式构象与重叠式构象) H H H H H H H H H H H H 重叠式构象 交叉式构象 60O Eclipsed Staggered The least stable conformation The least stable conformation The most stable conformation The most stable conformation Torsional barrier(转动能垒) 12.1 kJ·mol-1
ORGANIC CHEMISTRY Chapter 4 Conformational analysis of ethane 2.29A H H o Bond length: CH1.07, C--C154A o Bond angle:∠HCH1095 o The distance between two h atomS: 2, A o tomic radius of H: H=1.2 A Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 4 Conformational analysis of ethane H H H H H H 2.29 A Bond length C—H 1.07, C—C 1.54 Å Bond angle HCH 109.5 The distance between two H atoms 2.29 Å tomic radius of H γH = 1.2 Å