Comparison of the C-13 (C=N) chemical shifts of substituted N-(phenyl-ethylene)-anilines and substituted N-(benzylidene)-anilines

摘要

Comparison of C-13 NMR of C=N bond chemical shifts (C)(C=N) in substituted N-(phenyl-ethylene)-anilines XArC(Me)=NArY (XPEAYs) with that in substituted N-(benzylidene)-anilines XArCH=NArY (XBAYs) was carried out. The (C)(C=N) of 61 samples of XPEAYs were measured, and the substituent effect on their (C)(C=N) were investigated. The results show the factors affecting the (C)(C=N) of XPEAYs are quite different from that of XBAYs. A penta-parameter correlation equation was obtained for the 61 compounds, which has correlation coefficient 0.9922 and standard error 0.12ppm. The result indicates that, in XPEAYs, the inductive effects of substituents X and Y are major factors affecting the (C)(C=N), while the conjugative effect of them have very little effect on the (C)(C=N) and can be ignored. The substituent-specific cross-interaction effects between X and Y and between Me of C=N bond and substituent Y are important factors affecting the (C)(C=N). Also, the excited-state substituent parameter of substitute Y has certain contribution to the (C)(C=N). Copyright (c) 2015 John Wiley & Sons, Ltd.