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化学学报
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化学学报 ›› 1993, Vol. 51 ›› Issue (5): 444-450. 上一篇    下一篇

研究论文

含杂三元环化合物键强变化规律

周亚新;熊建章;潘道皑   

  1. 华东师范大学化学系
  • 发布日期:1993-05-15

The rules of changes of bond strengths in three member heterocyclic compounds with heteroatoms Be, B, N, O and S

ZHOU YAXIN;XIONG JIANZHANG;PAN DAOAI   

  • Published:1993-05-15

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用键强参数f~i, ~A~-B, f~A~-~B可定量地表达含杂三元环化合物CH2-CH2-X(X=Be, BH, CH2, NH, O及S)中成键情况及键强变化规律: 1. 无论在三元环中, 还是在C-X-C中, X=Be→O时, f~c~-~x随X中重原子的核电荷数Z递增而增大。其原因: X中重原子实对于价电子的有效核电荷数随其核电荷数Z的增大而增大。C-X的"键电荷"也随X的Z值递增。2. 当X=Be→O, 在形成CH2-CH2-X时, 较强键被削弱, 较弱键则增强, 致环内各-键键强和键长都有平均化的趋势。其原因为: 三元环分子中形成σ共轭的三中心键, C-X与C-C键共享"键电荷"。这种"σ-共轭效应"与π-共轭效应有相似处。3.由于硫的价电子云平均半径较大, 可向c-C提供更多共享电荷, 故在含S三元环化合物CH2-CH2-S中C-S键受到更大程度的削弱, C-C则更被增强。

关键词: 计算, 键参数, 三员杂环化合物, 分子轨道计算

Bond formation and bond strength variation in I (X = Be, BH, CH2, NH, O, S) were calculated by MO and expressed quant. by bond strength parameters. In I and in Me2X, C-X bond strength increases as the kernel charge increases from X = Be to X = O. During cyclization, the stronger bonds are weakened and the weaker bonds are strengthened because of a-conjugation in 3-centered bonds in I sharing bond charge, similar to the p-conjugation effect. Between X = O and X = S in I, S with its larger atomic radius can contribute more charge to C-C for sharing than O, resulting weakened C-X and strengthened C-C to the greatest degree.

Key words: CALCULATION, BOND PARAMETER, THREEMEMBER HETEROCYCLICS COMPOUNDS, MOLECULAR ORBITALS CALCULATIONS

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