NEW DEFINITION OF DEWAR-TYPE RESONANCE ENERGIES
NEW DEFINITION OF DEWAR-TYPE RESONANCE ENERGIES
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DOI：
10.1021/ja00426a013
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发表时间：
1976-01-01
影响因子：
15
通讯作者：
AIHARA, J
中科院分区：
文献类型：
--
作者：
AIHARA, J
为了用解析法估算共轭化合物的HMO共振能，本文用图论方法构造了一个参考多项式，即参考结构的特征多项式，从HMO特征多项式的系数中排除了x体系中环状组分的贡献。共振能定义为从原始化合物的HMO特征多项式计算的总x能量与从相应的参考多项式计算的总x能量之间的差。该方法可以应用于共轭烃，杂环，甚至离子物种。得到的共振能与Hess和Schaad的共振能非常一致，明显地属于杜瓦型。这些共振能的唯一性，没有歧义或任意参数化，是这种方法的特点。共振能和芳香性是共轭烃和杂环理论中的关键概念。到目前为止，分子轨道理论已经提供了许多关于芳香族稳定性的信息。[1]特别地，具有n个双键的共轭烃的总x能量经常与n个乙烯分子的总x能量进行比较。离域能被定义为这两个x能量之间的差，被认为是芳香性的度量。已发表的实验共振能都与这种HMO离域能有关。然而，共轭烃的离域能与它们的化学行为之间缺乏相关性，这明确表明离域能不能用来预测它们的芳香性。2
In order to analytically estimatethe HMO resonance energy for a conjugated compound, a reference polynomial, ie, a characteristic polynomial for the reference structure, is constructed by graph-theoretically excluding from the coeffi-cients of the HMO characteristic polynomial all contributions from cyclic components in the x system. The resonance energy is thendefined as the difference between the total x energy calculated from the HMO characteristic polynomial for the original compound and that calculated from the corresponding reference polynomial. The method can be applied to conjugated hydrocarbons, heterocycles, and even ionic species. The obtained resonance energies are in excellent agreement with those of Hess and Schaad, and are evidently of Dewar type. The uniqueness of these resonance energies, derived without ambiguities or arbitrary parametrization, is characteristic of this approach.Resonance energy and aromaticity are key concepts in the theory of conjugated hydrocarbons and heterocycles. So far, molecular orbital theories have provided much of the information concerning aromatic stability. 1 Especially, the total x energy of a conjugated hydrocarbon with n double bonds has often been compared with that of n ethylene mol-ecules. Delocalization energy, which is defined as the differ-ence between these two x energies, has been considered as a measure of aromaticity. IaThe published experimental resonance energies are all related to such HMO delocalization energies. 13 However, the lack of correlation between delo-calization energies for conjugated hydrocarbons and their chemical behavior definitely shows that the delocalization energies are disqualified from predicting their aromatici-ties. 2