Electrofugalities of 1,3-diarylallyl cations.
Electrofugalities of 1,3-diarylallyl cations.
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1,3-二芳基烯丙基阳离子的电离度
DOI：
10.1021/jo302766k
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
H. Mayr
中科院分区：
文献类型：
--
作者：
K. Troshin;H. Mayr
测定了不同取代的1,3-二芳烯丙基卤化物和羧酸盐在不同溶剂中的异裂解速率常数。用线性自由能关系logk1=sf（Nf+Ef）预测1,3-二芳烯基衍生物的杂解率（logk1），标准差为0.26，对应系数为1.82 ink1，最大偏差ink1为5。然而，一些系统性偏差是显而易见的。因此，当使用两种类型的离去基来确定电逸性参数时，1,3-二芳烯基羧酸酯总是反应更快，而1,3-二芳烯基氯化物总是反应更慢。由于1,3-二芳基烯基阳离子在溶剂溶解反应中生成更快，并且与亲核试剂的反应速度也比热力学稳定性相似的苯并羟基离子（即刘易斯酸）更快，因此可以得出结论，涉及1,3-二芳基烯基阳离子的反应比涉及苯并羟基离子的反应具有更低的本禀势垒。本文测定的1,3-二芳基烯丙基离子的电性参数与相应阳离子的亲电性参数以及前人报道的离子对动力学结果相结合，得到了1,3-二芳基烯丙基溶剂解的完整机理谱。
Heterolysis rate constantsk1of differently substituted 1,3-diarylallyl halides and carboxylates have been determined in various solvents. The linear free energy relationship logk1=sf(Nf+Ef) was found to predict the heterolysis rates (logk1) of 1,3-diarylallyl derivatives with a standard deviation of 0.26, corresponding to a factor of 1.82 ink1, and maximum deviation ink1of a factor of 5. Some systematic deviations are evident, however. Thus, 1,3-diarylallyl carboxylates always react faster and 1,3-diarylallyl chlorides always react more slowly than calculated by the quoted correlation equation when both types of leaving groups were used to determine the electrofugality parametersEf. As 1,3-diarylalyl cations are generated faster in solvolysis reactions and also react faster with nucleophiles than benzhydrylium ions of similar thermodynamic stabilities, i.e., Lewis acidities, one can conclude that the reactions involving 1,3-diarylallyl cations proceed with lower intrinsic barriers than those involving benzhydrylium ions. The electrofugality parametersEfof 1,3-diarylallylium ions determined in this work were combined with the electrophilicity parametersEof the corresponding cations as well as with the results on ion pair dynamics reported in preceding papers for generating the full mechanistic spectrum of 1,3-diarylallyl solvolyses.