Fluorine atoms incorporated into 1,5-hexadiene molecule should influence the kinetic as well as the thermodynamic parameters of [3,3] sigmatropic rearrangement (Cope rearrangement). Within few decades is has been documented that this transformation proceeds in a concerted manner, rather than stepwise with some radical intermediates involved. Few new terminally fluorinated 1,5-hexadienes (compounds 3, 5A, 7, 9 and 5B) have been synthesized. The activation parameters of rearrangement have been determined and compared with those known for hydrocarbon analogues. While systems developing chair-like transition states (compounds 3 and 5) showed close similarity with hydrocarbon analogues (compound 1), those developing boat-like transition states (compounds 7, 9 and 5B) may proceed through radical stepwise mechanism. Computational studies of the transition states were carried out, showing that only ab initio methods (MP2 and especially DFT) can give approximate correlation with experimental data, whereas in the case of hydrocarbon analogues even simple semiempirical methods (AM1) were reliable enough to reproduce experimental results.
氟原子被并入1,5-己二烯分子中应该会影响[3,3]异构重排(Cope重排)的动力学和热力学参数。几十年来已经有记录表明,这种转化是以协同方式进行的,而不是逐步进行,其中涉及一些自由基中间体。已经合成了一些新的末端氟化的1,5-己二烯(化合物3、5A、7、9和5B)。已确定了重排的活化参数,并与已知的碳氢类似物进行了比较。发展出椅状过渡态的体系(化合物3和5)与碳氢类似物(化合物1)显示出密切相似性,而发展出船状过渡态的体系(化合物7、9和5B)可能会通过自由基逐步机制进行。已进行了过渡态的计算研究,结果显示只有从头算方法(MP2和尤其是DFT)才能与实验数据大致相关,而在碳氢类似物的情况下,甚至简单的半经验方法(AM1)也足以可靠地再现实验结果。