直链共轭多烯电子的极化率随碳链增长变化规律的研究

Study on Varying Rule of the Electron Polarizability of Straight-chain Polyene with Increasing of Carbon-chain Lenth

本文采用引入外电场微扰的量子化学方法计算了直链共轭多烯Ｈ－（ＣＨ＝ＣＨ）ｎＨ（ｎ＝１，２，…，１５）电子的极化率。取乙烯电子的极化率ａ（１）为参照值，首次运用关系式ａ（ｎ）＝ａ（ｎ）。ａ（１）．ｎ分析了系列多σ、π和全价电子的极化率随ｎ增大的变化规律。结果表明，随着ｎ的增大，ａ＾σ（ｎ）始终近近于１，即有α＾σ（ｎ）＝α＾σ（１）．ｎ；而α＾π（ｎ）开始增大明显，然后增幅逐渐降低。

In this paper, the quantum chemistry method introduced within external electric perturbation field approach is used to calculate the electron polarizability of straight-chainpolyene H-(CH = CH)n-H(n= 1, 2, ……, 15). Further, we adopt the α(l), the electronpolarizability of ethene, as the value of reference, using the relational expresion α(n) = a(n) · α(1) · n to discuss the varying rule of electron polarizability of σ, π and total electron system with the increasing of n. The results show: (1) the aσ(n) approach a constant 1 very much, i.e. ασ(n) = ασ(1) · n; (2) the aπ(n) increases obviously at first, then the increasing vilocity decreases gradually, when the n is over a certain value n0 the απ(n) tend to a limit, i.e. whenn <n0, απ(n) = aπ(n) · απ(l) · n and aπ(n)>aπ(n-1), when n≥n0, απ(n) = aπ(n0) · απ(1) · n; total valence electrons' is same as π electrons'. Otherwise, we use the picture of displacement of gravity-center of electron distribution to describe this conclusion.