取代基立体效应对氮苄叉苯胺氢核磁共振化学位移的影响  

Substituent Steric Effect on the ~1H NMR Chemical Shifts of Benzylideneanilines

作　　者：程时茂 曹晨忠[1] Cheng Shimao;Cao Chenzhong(Key Laboratory of Theoretical Organic Chemistry and Function Molecule,Ministry of Education,Key Laboratory of QSAR/QSPR of Hunan Provincial University,School of Chemistry and Chemical Engineering,Hunan University of Science and Technology, Xiangtan 411201, China)

机构地区：[1]湖南科技大学化学化工学院理论有机化学与功能分子教育部重点实验室分子构效关系湖南省普通高等学校重点实验室

出　　处：《湖南科技大学学报（自然科学版）》2019年第2期96-101,共6页Journal of Hunan University of Science And Technology：Natural Science Edition

基　　金：国家自然科学基金资助项目(21672058)

摘　　要：合成了44个2,4'-二取代氮苄叉苯胺,2-XArCH=NArY-4 (o-XBAY-p)化合物,以核磁共振(NMR)~1H氢谱和^(13)C碳谱确定其结构,指认出桥基CH=N上氢的化学位移δH(CH=N).定量研究取代基效应对δH(CH=N)的影响,将o-XBAY-p的δH(CH=N)与文献报道二芳基希夫碱p/m-XBAY-p/m的δH(CH=N)进行了比较.结果表明:在o-XBAY-p中,邻位基团的立体效应,严重削弱了取代基X和Y电子效应对δH(CH=N)的影响,使δH(CH=N)与取代基X和Y的电子效应常数之间没有良好的定量关系,并且使o-XBAY-p的δH(CH=N)比p/m-XBAY-p/m的δH(CH=N)普遍增大.本文观察到的这一新的实验现象,以前未见报道,它对于利用核磁共振1H NMR化学位移解析希夫碱化合物的分子结构有重要参考价值.Forty-four samples of 2,4'-disubstituted benzylideneanilines,2-XArCH = NArY-4( o-XBAY-p)were synthesized,and their molecular structures were characterized by the ~1H NMR and ^(13)C NMR spectra. The ~1H chemical shift values δH(CH=N) of CH=N bridge groups were determined. The effect of substituents X and Y on the δH(CH=N) were investigated quantitatively. Also the δH(CH=N) of o-XBAY-p were compared with that of bi-aryl Schiff bases p/m-XBAY-p/m reported by literature. The results show that,in the o-XBAY-p molecules,the steric effect of ortho-substituents seriously weakens the influence of the substituent electronic effect of X and Y on the δH(CH=N),so that there is no good quantitative relationship between the δH(CH=N)and the substituent electronic effect constants of X and Y. Moreover,the steric effect of ortho-substituents generally increases the δH(CH=N) of o-XBAY-p compared to that of p/m-XBAY-p/m. The new experimental phenomenon observed was not reported before. It is an important reference for the molecular structure analysis of schiff base compounds by means of the chemical shift of ~1H NMR spectrum.

关 键 词：核磁共振(NMR) 1H NMR化学位移 取代基电子效应 取代基立体效应 氮苄叉苯胺 

分 类 号：O621.1[理学—有机化学]