Influences of polarizability effect of alkyl group and homoring competition effect of substituents on the NMR spectra of salen‐type Schiff base
作者:Bai‐ying Wei、Chen‐zhong Cao、Chao‐tun Cao
DOI:10.1002/mrc.5131
日期:2021.7
explore the effect of alkyl groups and substituents attached to aromatic ring on the chemical shifts 63 title compounds were synthesized. Their 1 H NMR and 13 C NMR spectra were obtained; and the effects of the alkyl chain length and substituents on the chemical shifts (δH (CH=N), δC (CH=N), δH (OH) and δC (C-OH)) were studied. The results show that: (1) The alkyl polarizability effect index (PEI)
Salen型席夫碱是一类重要的化合物,应用广泛。为了探索烷基和连接到芳环上的取代基对化学位移的影响,合成了 63 种标题化合物。获得了它们的 1 H NMR 和 13 C NMR 谱图;并研究了烷基链长和取代基对化学位移(δH(CH=N)、δC(CH=N)、δH(OH)和δC(C-OH))的影响。结果表明:(1)烷基极化效应指数(PEI)对上述四个原子的化学位移有重要影响,随着PEI的增加,δH(CH=N)和δc(CH= N)减少,而δH(OH)和δC(C-OH)的值增加。(2)芳环上的取代基X对化学位移的影响与其位置有关,取OH或CH=N为参考。至于取代基对化学位移的影响,哈米特常数σ(X)-OH和激发态取代基参数σ CC ex X - OH以OH为参考的影响与σ(X)-CH= N 和 σ CC ex X - CH = N 以 CH=N 为参照,存在取代基的“同源竞争效应”。(3) X与