(CF3·CFCFX) have been treated with antimony pentafluoride in sulphur dioxide at low temperatures. When X =p-MeO·C6H4, both cis- and trans-isomers gave the same long-lived allyl cation, which was observed by n.m.r. spectroscopy; quenching with methanol gave methyl 2,3-difluoro-3-(p-methoxyphenyl)-acrylate. In the case X = OMe, there is some C-1, C-3 interaction in the observed allyl cation; in the cases X =
聚
氟丙烯(CF 3 ·CF CFX)已在低温下用
五氟化锑和
二氧化硫处理。当X =p- MeO·C 6 H 4时,顺式和反式异构体均具有相同的长寿命
烯丙基阳离子,这是通过核磁共振光谱法观察到的。用
甲醇淬灭,得到
甲基2,3-二
氟-3-(p-
甲氧基苯基)-
丙烯酸酯。在X = OMe的情况下,观察到的
烯丙基阳离子中存在一些C-1,C-3相互作用;在X = Ph或Me物种的情况下,无法表征。用
六氟丙烯未观察到长寿命离子,但发生了二聚作用。由1,2-二
甲基和1,2-二甲
氧基-
3,3,4,4-四氟环丁烯生成了环ob离子。这些离子的电荷集中在C-1和C-3处。