J. Iran. Chem. Soc., Vol. 6, No. 4 December 2009, pp.808~811.

Current location: JICS Archive > Vol. 6 > No. 4 > Articles : 18

Substituent Effects in the 13C NMR Chemical Shifts of Para-(para-substituted benzylidene amino)benzonitrile and Para-(ortho-substituted benzylidene amino)benzonitrile

G.F. Fadhila and A.H. Essab,*

aDepartment of Chemistry, College of Science, University of Dohuk, Dohuk, Iraq
bDepartment of Chemistry, College of Science, University of Basrah, Basrah, Iraq

13C NMR chemical shifts were measured in CDCl3 for two series of substituted benzylidene anilines. The substituted benzylidene anilines p-X-C6H4CH=NC6H4-p-CN p-X-C6H4CH=NC6H4-o-CN (X = NO2, F, Cl, Br, H, Me, MeO, NMe2). The substituent dependence of ×C(C=N) was used as a tool to study electronic substituent effects on the azomethine unit. The benzylidene substituents X have a reverse effect on ×C(C=N): electron-withdrawing substituents cause shielding, while electron-donating ones do the reverse, the resonance effects clearly predominating over the inductive effects. Additionally, the presence of a specific cross-interaction between X and C=N could be verified. The electronic effects of the neighboring aromatic ring substituents systematically modify the sensitivity of the C=N group to the electronic effects of the benzylidene substituents. These results can be rationalized in terms of the substituent-sensitive balance of the electron delocalization (mesomeric effects).

Keywords: N-Benzylideneaniline, Substituent effects, DSP analysis, Reynolds' model

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