苯多烯共轭体系反向端基效应的研究

STUDIES ON THE EFFECT OF OPPOSITE TERMINAL GROUPS IN PHENYL POLYENIC CONJUGATIVE SYSTEMS

本文合成了七个系列的化合物(A=B(CH=CH)-X=Y,A=B-=-NO_2,-X=Y=-CHO、-COMe、-CN、-NO_2;A=B-=-CN,-X=Y=-CN、-CHO;A=B-=-H,-X=Y=-NO_2),通过UV、XPS、^(13)CNMR、量化计算等对苯多烯共轭体系的反向端基效应进行了研究.结果表明:反向端基效应存在于苯多烯及其它芳香共轭体系之中.当两个末端基团相同时(A=B-=-X=Y),烯链末端的基团为端基,苯环上的基团为反向端基,反向端基不包括苯环在內.当两个末端基团不同时(A=B-≠-X=Y),则共軛能力较弱的基团成为反向端基.反向端基效应可用△Ns定量描述,△Ns值均小于1,其大小约依-CN、-COMe、-CHO、-NO_2增强.反向端基系列化合物的λ_(max)可按引入反向端基当量的同系方程10^(-4)v=a+b(1/2))计算,计算值与实验值基本符合.

In this paper, 7 homotogous series (A=B=-CH=CH_n X=Y,A=B-=-NO_2,-X=Y=-CHO,-COMe,-CN,-NO_2; A=B-=-CN,-X=Y=-CHO,-CN; A=B=H-,-X=Y=-NO_2) were synthesized; the effect of opposite terminal groups in pheny polyenic eonjugative systems has been studied by means of UV, XPS, ^(13)C NMR and quantumn chemical calculation.The results show that: 1.The effect of opposite terminal groups exists in phenylpolyenic and other aromatic conjuative systems.2.When A=B and X=Y are the same, the group (X=Y) connected at polyenie chain is a terminal group, while the group (A=B) connected at phenyl is an opposite terminal group which does not contain phenyl itself.When the two groups are different (A=B-≠X=Y), the one with weaker conjugativc power plays the rote of the opposite terminal group.3.The effect of opposite terminal groups increases in the order of-CN,-COMe,-CHO,-NO_2 and can be quantitatively described with substitute equivalent ΔN_2.The λmax of compound containing an opposite terminal group can be calculated by the homologous equation 10^(-4)v—=a+b(1/2)^(2/N'-Sa), most of the calculated values are in agreement with experiment results.