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化学学报
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化学学报 ›› 1992, Vol. 50 ›› Issue (5): 422-426. 上一篇    下一篇

研究论文

有机氟化合物量子化学研究 I: 二氟乙炔分子中化学键特性的从头计算

方志刚;蒋华良;潘道皑;周伟良   

  1. 华东师范大学化学系
  • 发布日期:1992-05-15

Quantum chemical studies of organofluoric compounds I: Ab initio studies of the properties of chemical bonds of difluoroacetylene

FANG ZHIGANG;JIANG HUALIANG;PAN DAOAI;ZHOU WEILIANG   

  • Published:1992-05-15

PDF

426

被引次数

6

实验发现, F-C≡C-F与H-C≡C-H相比, 其C≡C三重键的离解能要小250.8kJ/mol,而该键的键长却比C~2H~2的短。这与"键越短键就越强"的传统看法不一致。我们通过从头计算研究, 发现主要原因是C~2F~2分子中F原子的孤对电子对C≡C三重键起反键作用, 从而削弱了C≡C三重键的强度; F原子的吸电子性又使C的原子轨道收缩效应增强,而使得C≡C三重键变短。

关键词: 量子化学, 化学键, 从头计算法, 有机氟化合物, 键参数, 键长, 二氟乙炔, LCAO-MO-SCF法

The dissociation energy of CYC triple bond of C2F2 is lower by 250.8 kJ.mol-1 than that of C2H2, but the CYC triple bond length of C2F2 is shorter than that of C2H2. This phenomenon does not accord with the conventional view - i.e., the shorter the bond is, the stronger the bond will be. According to the ab initio calcns. the main reasons are (1) the contributions of the lone pair electrons of F to CYC triple bond are antibonding, which weaken the CYC triple bond; (2) the attraction of electrons by F enlarges the contracting effect of AOs of C, which shortens the CYC triple bond.

Key words: QUANTUM CHEMISTRY, CHEMICAL BONDS, AB INITIO CALCULATION, ORGANO FLUORINE COMPOUNDS, BOND PARAMETER, BOND LENGTH

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