The cis-trans isomerization of by Br2 in CCl4 is described. A bridged bromonium cation α to CF2 is destabilized resulting in a carbocation bromide ion pair at the β-carbon capable of free rotation and loss of bromine to form . A CF2 group appears to be more effective in promoting isomerization than aryl in the case of stilbenes.
描述了Br 2在CCl 4中的顺反异构化。与CF 2桥接的
溴阳离子α不稳定,导致β-碳上的碳正离子
溴离子对能够自由旋转并损失形成
溴。在
芪丁酯的情况下,CF 2基团在促进异构化方面似乎比芳基更有效。