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首页> 外文会议>Advances in Computational Methods in Sciences and Engineering 2005 vol.4A; Lecture Series on Computer and Computational Sciences; vol.4A >DFT Study and NBO (Natural Bond Orbital) Analysis of the Mutual Interconversion of Cumulene Compounds
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DFT Study and NBO (Natural Bond Orbital) Analysis of the Mutual Interconversion of Cumulene Compounds

机译：DFT研究和NBO（自然键轨道）分析Cumulene化合物相互转化的过程

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摘要

The Becke, Lee, Yang and Parr density functional (B3LYP) method was used to investigate the configurational properties of allene (1,2-propadiene) (1), 1,2,3-butatriene (2), 1,2,3,4-pentateriene (3), 1,2,3,4,5-hexapentaene (4), 1,2,3,4,5,6-heptahexaene (5), 1,2,3,4,5,6,7-octaheptaene (6), 1,2,3,4,5,6,7,8-nonaoctaene (7) and 1,2,3,4,5,6,7,8,9-decanonaene (8). B3LYP/6-31G~* level of theory showed that the mutual interconversion energy barrier in compounds 1-8 are 50.14, 31.49, 28.75, 20.37, 19.32, 14.31, 14.00 and 10.49 kcal mol~(-1), respectively. The results showed a linear relationship between the corresponding B3LYP/6-31G~* mutual interconversion energy barriers and the average C=C double bond lengths (d), in the ground state geometries of cumulene compounds. The results showed also that the difference between the (d) values in cumulene compounds 1 and 2 is larger than those between 7 and 8, which suggest that with large n (number of carbon atoms in cumulene chain), the d values approach to a limiting value. Also, NBO//B3LYP/6-31G~* results revealed that the π-bond occupancies decrease from 1 to 8, and inversely, the π-antibond occupancies increase from compound 1 to compound 8. The difference between the average of π-bonds and π-antibond occupancies (Δ= π_(occupancy) - π~*_(occupancy) could be considered as a criteria for the mutual interconversion in compounds 1-8. These Δ values decrease from compound 1 to compound 8 series as following: 1.92087, 1.80788, 1.75314, 1.70637, 1.67144, 1.64337, 1.62065 and 1.60170, respectively, as calculated by B3LYP/6-31G~* level of theory. The decrease of Δ values for compounds 1-8, follow the same trend as the barrier heights of mutual interconversion in compounds 1-8. Accordingly, besides the allylic resonant stabilization effect in the transition state structures, the results revealed, particularly, that the Δ value could be considered as significant criteria for the mutual interconversion in cummulene compounds 1-8.
机译：使用Becke，Lee，Yang和Parr密度泛函（B3LYP）方法研究丙二烯（1,2-丙二烯）（1），1,2,3-丁三烯（2），1,2,3的构型性质，4-戊三烯（3），1,2,3,4,5-六戊烯（4），1,2,3,4,5,6-庚七己烯（5），1,2,3,4,5， 6,7-八庚烯（6），1,2,3,4,5,6,7,8-壬八烯（7）和1,2,3,4,5,6,7,8,9-癸二烯（ 8）。 B3LYP / 6-31G〜*的理论水平表明，化合物1-8的互变能垒分别为50.14、31.49、28.75、20.37、19.32、14.31、14.00和10.49 kcal mol〜（-1）。结果表明，在异丙苯化合物的基态几何结构中，相应的B3LYP / 6-31G〜*相互转换能垒与平均C = C双键长度（d）之间存在线性关系。结果还表明，异丙苯化合物1和2中的（d）值之间的差异大于7和8之间的差异，这表明当n（异丙苯链中的碳原子数）较大时，d值接近a极限值。同样，NBO // B3LYP / 6-31G〜*结果表明，π键的占有率从1降低到8，反之，π反键的占有率从化合物1到化合物8都增加了。化合物1-8中相互键合的标准可以考虑使用键和π-反键占据率（Δ=π_（占有率）-π〜* _（占有率）。这些Δ值从化合物1减少到化合物8系列：按照B3LYP / 6-31G〜*理论水平计算，分别为1.92087，1.80788，1.75314，1.70637，1.67144，1.64337，1.62065和1.60170。化合物1-8的Δ值下降趋势与化合物1-8的下降趋势相同。化合物1-8互变的势垒高度，因此，除了过渡态结构中的烯丙基共振稳定作用外，结果特别表明，Δ值可被视为异丙苯化合物1-互变的重要标准。 8。

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