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首页> 外文期刊>Chemistry: A European journal >Is Cyclopropane Really the σ-Aromatic Paradigm?
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Is Cyclopropane Really the σ-Aromatic Paradigm?

机译：环丙烷真的是σ-芳香范式吗？

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Dewar proposed the σ-aro-maticity concept to explain the seem-ingly anomalous energetic and magnet-ic behavior of cyclopropane in 1979.While a detailed, but indirect energeticevaluation in 1986 raised doubts—"There is no need to involve 'σ-aroma-ticity',"—other analyses, also indirect,resulted in wide-ranging :estimates ofthe 0-aromatic stabilization energy.Moreover, the aromatic character of"in-plane", "double", and cyclically de-localized σ-electron systems now seemswell established in many types of mole-cules. Nevertheless, the most recent analysis of the magnetic properties ofcyclopropane (S. Pelloni, P. Lazzeretti,R. Zanasi, J. Phys. Chem. A 2007, 111,8163-8169) challenged the existence ofan induced 0-ring current, and provid-ed alternative explanations for the ab-normal magnetic behavior. Likewise,the present study, which evaluates the0-aromatic stabilization of cyclopro-pane directly for the first time, fails to find evidence for a significant energeticeffect. According to ab initio valencebond (VB) computations at theVBSCF/cc-PVTZ level, the 0-aromaticstabilization energy of cyclopropane is,at most, 3.5 kcal mol~(-1)relative to pro-pane, and is close to zero when n-butane is used as reference. Trisilacy-clopropane also has very little σ-aro-matic stabilization, compared to Si3H8(6.3 kcal mo1-1) and Si41-11, (4.2 kcalmoll. Alternative interpretations ofthe energetic behavior of cyclopropane(and of cyclobutane, as well as their sil-icon counterparts) are supported.
机译：杜瓦（Dewar）在1979年提出了σ-芳香族概念来解释环丙烷的看似异常的高能和磁行为。尽管在1986年进行了详细而间接的能量评估，但人们对此产生了疑问：“无需涉及'σ-芳香族-ticity'，“-其他分析，也间接地导致了：0-芳族稳定能的估计。此外，”面内“，”双“和周期性离域σ电子的芳族特征现在看来，在许多类型的分子中都建立了良好的体系。然而，对环丙烷的磁性的最新分析（S. Pelloni，P. Lazzeretti，R. Zanasi，J. Phys。Chem。A 2007，111,8163-8169）挑战了感应0环电流的存在，并且提供了有关正常磁行为的替代解释。同样，本研究首次直接评估环丙烷的0-芳烃稳定度，但也没有找到显着的能量效应的证据。根据在VBSCF / cc-PVTZ水平上的从头价键（VB）计算，环丙烷的0-芳族稳定能最多为3.5 kcal mol〜（-1）相对于丙烷，当n为n时接近零。 -丁烷用作参考。与Si3H8（6.3 kcal mo1-1）和Si41-11（4.2 kcalmoll）相比，三硅烷基氯丙烷也几乎没有σ-芳族稳定性。对环丙烷（和环丁烷及其硅的高能行为的另一种解释） -icon对应项）。

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