Elimination and addition reactions. Part 43. Eliminative fission of cyclobutanes and the relationship between strain and reactivity in cyclobutanes and cyclopropanes
作者:Harold A. Earl、Charles J. M. Stirling
DOI:10.1039/p29870001273
日期:——
Eliminative fission of cyclobutanes has been compared with that of analogous cyclopropanes; reactivity differences of 103.7—104.8 have been determined. In both sets of compounds, mechanisms have been shown to involve rate-determining ring fission. The possibilities that the large reactivity differences between the comparably strained systems are due either to peculiarity in the cyclobutane structures
已将环丁烷的消除裂变与类似的环丙烷的消除裂变进行了比较。反应活性差异10 3.7 —10 4.8已经确定。在这两种化合物中,机制均已显示出决定速率的环裂变。相比之下,由于环丁烷结构的特殊性或它们异常缓慢的去质子性,在相应应变的体系之间存在较大的反应性差异的可能性被拒绝了。对这两个系统中的应变的分析表明,当发生环裂变时,环丁烷过量的焓的分散对环中键的延伸的敏感性比对环丙烷的敏感性低。将这些系统的行为与在其他反应中裂解环丙烷和环丁烷进行了比较。结果非常相似。已经使用MINDO3程序对环丙基甲基和环丁基甲基碳负离子的消除裂变进行了计算。这些显着地非常接近地再现了各个环尺寸裂变时在能量最大值处的物质形成热之间的差异。环丁烷裂变的最大值沿反应坐标向产物相当大地位移。