24BCis- Trans isomerism顺反异构 H H H NO Cis-trans Cis Cis-1.2-dichloroethene H H C NO CiS-trans Trans Trans-1.2-dichloroethene2.4B Cis-Trans isomerism 顺 反 异 构 H H H H NO Cis-trans Cl H Cl H Cl H H Cl Cis Trans Cis-1,2-dichloroethene Trans-1,2-dichloroethene Cl H Cl H Cl H H Cl Cl Cl H H NO Cis-trans