168213-20-5Relevant academic research and scientific papers
Investigation of the substituent specific cross-interaction effects on 13C NMR of the C=N bridging group in substituted benzylidene anilines
Cao, Chenzhong,Lu, Bingtao,Chen, Guanfan
, p. 335 - 341 (2011)
The substituent effect on 13C NMR of the C=N in benzylidene anilines XPhCH=NPhY was investigated, in which the substituents X and Y are in p-position or in m-position of the two aromatic rings. The substituent effects including the inductive effects of X and Y, the conjugative effects of X and Y, and the substituent specific cross-interaction effect were put into one model to quantify the 13C NMR chemical shift δC(C=N) of the C=N in XPhCH=NPhY. A penta-parameter correlation equation with correlation coefficient 0.9975 and standard error 0.17 ppm was obtained for 80 samples of compounds. The result shows that the substituents X and Y have an opposite effect on the δC(C=N). The electron-withdrawing effects of X decrease the δC(C=N); while the electron-donating effects of X increase the δC(C=N). In contrast, the electron-withdrawing effects of Y increase the δC(C=N); while the electron-donating effects of Y decrease the δC(C=N). A new substituent specific cross-interaction effect parameter δσ2 was proposed, which indicates that the most substituent specific cross-interaction effect exists in the pair of max electron-withdrawing group (EWG) and max electron-donating group (EDG) or the pair of max EDG and max EWG. Further to verify the obtained correlation equation, 15 samples of model compounds were prepared and their δC(C=N) was measured in this work. The predicted δC(C=N) values with the obtained equation are in good agreement with the measured ones for these prepared compounds, which confirmed the reliability of the obtained equation.
