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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Vibrational Anharmonicities and Reactivity of Tetrafluoroethylene
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Vibrational Anharmonicities and Reactivity of Tetrafluoroethylene

机译：四氟乙烯的振动不谐波和反应性

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摘要

Compared to ethylene and its nonfluorinated derivatives, C_2F_4 is peculiar in many reactions. It very easily adds to radicals and prefers formation of four-membered rings over Diels-Alder reactions. This has been rationalized by the preference of fluorine for carbon sp~3 hybridization, which is possible on opening of the double bond. Another property, the thermal dissociation of the C=C bond, has been explained by the stabilization of the product (CF_2) by back-bonding. Here, it is attempted to correlate such properties with vibrational constants, in particular for C=C stretching and twisting and for carbon pyramidalization. The only force constant found to be lowered compared to ethylene is that for trans pyramidalization (ν_8), and CC bond softening on ν_8 distortion is indicated by the conspicuously large magnitude of anharmonic constant, x_(18). Both observations can be rationalized by a valence-bond model that predicts a trans bent structure on weakening the CC bond. Conclusions are drawn about the dissociation path and peculiarities of the potential. Other anharmonicities, both experimental and calculated and some in ~(12)C~(13)CF_4 and ~(13)C_2F_4, are also discussed. In particular some strong Fermi resonances are identified and their effects accounted for.
机译：与乙烯及其非氟化衍生物相比，C_2F_4在许多反应中是特殊的。它很容易添加到自由基中，并且比 Diels-Alder 反应更喜欢形成四元环。这已经合理化了氟对碳sp~3杂化的偏好，这在双键打开时是可能的。另一个特性，即 C=C 键的热解离，可以通过反键稳定产物 （CF_2） 来解释。在这里，试图将这些特性与振动常数相关联，特别是对于C=C拉伸和扭曲以及碳金字塔化。与乙烯相比，唯一发现的力常数是反式锥体化（ν_8），ν_8畸变时的CC键软化由非谐波常数x_（18）的显著大幅度表示。这两个观察结果都可以通过价键模型来合理化，该模型预测了 CC 键减弱的反式弯曲结构。得出了关于解离路径和电位特性的结论。还讨论了其他非谐波，包括实验和计算的，以及~（12）C~（13）CF_4和~（13）C_2F_4中的一些不和谐。特别是，发现了一些强费米共振，并解释了它们的影响。

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