Chemical deformation densities. 1. Principles and formulation of quantitative determination
Chemical deformation densities. 1. Principles and formulation of quantitative determination
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化学变形密度。
DOI：
10.1021/ja00200a006
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发表时间：
1989
影响因子：
15
通讯作者：
L. Mensching
中科院分区：
文献类型：
--
作者：
W. Schwarz;K. Ruedenberg;L. Mensching
结论虽然LRU的势能面给出了I和II相互转化势垒的合理值，但它们的中心势垒太高，并且它们预测了在红外和微波光谱中没有观察到的稳定弯曲构象的存在。在这项工作中，我们已经确定了改进的势能面的氧类似物的环己烯。每一个都有对应于扭曲构象的能量最小值。弯曲构象是在鞍点的表面上，并不是能量稳定的。这里确定的最低能量结构的平面性和thetrist角的障碍是略高于从MM2和微波研究确定的，但比以前的振动调查更好的协议。势能面很好地定义在较低的能量，但更差的中心势垒的区域中确定的振动数据。因此，虽然我们确信这里报告的屏障比LRU或DKSW的屏障好得多，但它们的测定置信度与四元环和五元环分子的屏障不同。尽管如此，这项工作的结果，当与NMR和微波结果一起观察时，有助于提供这四个分子构象能量差异的连贯图像。作者感谢国家科学基金会和罗伯特A。Welch基金会提供资金支持。
ConclusionsAlthough LRU’s published potential energy surfaces give reasonable values for barriers to interconversionfor I and II, their central barriers are too high and they predict the presence of stable bent conformations which have notbeen observed in the infrared and microwave spectra. In this work we have determined improved potential energy surfaces for the oxygen analogues of cyclohexene. Each of these has energy minima corresponding to thetwisted conformations. The bent conformations are at saddle points on the surfaces and are not energetically stable. The barriers to planarity and thetwist angles of the lowest energy structures determined here are somewhat higher than those determined from MM2 and microwave studies but are in much better agreement than the previous vibrational investigations. The potential energy surfaces are well defined by vibrational data at lower energies but are more poorly determined in the region of the central barrier. Thus, while we are confident that the barriers reported here are considerably better than those of LRU or DKSW, they are not determined with the same confidence as barriers for four-and five-membered ring molecules. 1" 4** Nonetheless, the results of this work, when viewed together with the NMR and microwave results, help provide a coherent picture of the conformational energy differences for these four molecules.Acknowledgment. The authors thank the National Science Foundation and the Robert A. Welch Foundation for financial support.