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对于久有争论的、极性(和/或可极化性)因素是否能影响自由基加成定位选择性的问题,用给电子性环丙基和三个氟烯的反应进行了验证。实验选用了四个温度和两种溶剂——非极性的异辛烷(Oct)和极性的缩二乙二醇二甲醚(Dgl),测定了衡量定位选择性的各R值,以及在两种溶剂中的活化能差与前置参数比。实得数据显示极性因素在上述反应中具有至少与位阻因素同等的重要性。本工作首次发现了自由基加成反应定位选择性对于反应介质的依赖性;这一溶剂效应可用SE值来表达。本文还讨论了在加成反应过渡络合体中极性因素如何起作用的问题,指出若干顺式1,2-取代乙烯12较其相应反式异构体13更为稳定的现象,可从“歪电子云”的简单物理模型得到合理解释以及讨论了本文结论在联系和指导生产、科研实践中的意义。
The question of whether the long-arguing, polar (and / or polarizable) factors can affect the selectivity of free radical addition localization was verified by the reaction of an electron donating cyclopropyl group with three fluoroolefins. Four temperatures and two solvents, non-polar isooctane (Oct) and polar diglyme (Dgl), were chosen for the experiment. R values for the selectivity of the positioning were determined, and The difference in activation energy between the two solvents was compared with the pre-parameters. The real data show that the polar factor has the same importance in the above reaction as the steric factor. This work first discovered the dependence of the selectivity of the radical addition reaction on the reaction medium; this solvent effect can be expressed as SE. The paper also discusses the issue of how polar factors work in the transition-addition complex and points out that the phenomenon of some cis-1,2-substituted ethene 12 is more stable than its corresponding trans isomer 13, The simple physical model of “crooked electron cloud” is reasonably explained and the significance of this conclusion in linking and directing production and scientific research practice is discussed.