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Long‐range transmission of substituent effects on 13 C NMR chemical shifts of imine carbon in benzylidene anilines
Author(s) -
Fang Zhengjun,
Cao Chenzhong,
Wu Weihe,
Wang Lu
Publication year - 2013
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.3077
Subject(s) - chemistry , substituent , imine , chemical shift , aniline , context (archaeology) , inductive effect , chemical bond , carbon 13 nmr , conjugated system , carbon fibers , resonance (particle physics) , crystallography , computational chemistry , stereochemistry , organic chemistry , atomic physics , materials science , physics , composite number , composite material , catalysis , paleontology , polymer , biology
The 13 C NMR chemical shifts of six kinds of substituted benzylidene anilines, with different backbone conjugation length, have been used as a probe to investigate the long‐range transmission of substituent effects. In this context, it was found that for substituents Y at the aniline unit, the transmission of the inductive and conjugative effects depend on the chemical bond numbers n (Y) between Y and the imine carbon, and the parameters n (Y) −2 σ F (Y) and n (Y) −2 σ R (Y) are suitable to scale the corrected inductive and conjugative effects, respectively. However, for substituents X, the chemical bond numbers n (X) between X and the imine carbon influences only the transmission of inductive effects of X, and the n (X) −2 σ F (X) item is appropriate to evaluate the modified inductive effects of X. Similarly, Δσ (cor) 2 was proposed to describe the transmitted effect of the cross‐interaction effect. With the parameters n (X) −2 σ F (X), σ R (X), n (Y) −2 σ F (Y), n (Y) −2 σ R (Y), Δσ (cor) 2 , and δ C (parent), the δ C (C = N) values of 181 samples can be well correlated. The correlation coefficient is 0.9957, and the standard derivation is only 0.23 ppm. Moreover, the multi‐parameter correlation equation is predicted well the δ C (C = N) of other 25 samples of designed conjugated benzylidene anilines. Copyright © 2012 John Wiley & Sons, Ltd.