Substituent effects on the stretching vibration of C═N in multi‐substituted benzylideneanilines

Abstract

Forty-nine samples of 3,4′/4,3′/3,3′-disubstituted benzylideneanilines (XBAYs) and 52 samples of multi-substituted XBAYs were synthesized, and their infrared absorption spectra were recorded in this paper. On the basis of the stretching vibration frequencies ν C═N of C═N bridging bond of 158 samples of substituted XBAYs (including 57 samples of 4,4′-disubstituted XBAYs from reference and 101 samples of substituted XBAYs synthesized in this paper), an extensional research of substituent effects on the ν C═N values from 4,4′-disubstituted XBAYs to multi-substituted XBAYs was made. A modified equation for quantifying the ν C═N values of multi-substituted XBAYs was obtained (shown as Equation (3)). Equation (3) indicates that the excitedstate substituent constant of Y and the substituent specific cross-interaction effect between X and X cannot be ignored for the quantitative regression analysis of the ν C═N values of multi-substituted XBAYs. Compared with Equation (1), Equation (3) has a wider application and more accuracy in quantifying the ν C═N values of substituted XBAYs.

Determining the excited‐state substituent constants of furyl and thienyl groups

“…In addition, we also collected the ν max values of 14 samples of 3′/4′‐disubstituted Schiff bases (PhCH═NArY) (Table , nos. 1‐14, reported by Wang et al and Chen et al). A regression analysis of the ν max values of the 26 compounds was made against the substituent constants, and Equation was obtained.…”

“…1‐8 was taken from Chen et al the λ max, exp of nos. 9‐14 was taken from Wang et al The rest of λ max, exp was obtained by this work.…”

“…Later, Jiang et al proposed a spin‐delocalization effect constant and combined with Hammett constant to correlate the optical properties of some organic compounds, in which the correlation was much improved. In 2008, Cao et al proposed an excited‐state substituent constant to express the effect of substituents on the properties of compounds at excited state, and then we used the to correlate quantitatively the UV absorption spectra and reduction potential of substituted benzene, substituted stilbene, and Schiff bases . We observed that the UV absorption spectra were mainly affected by the for the substituted benzene and substituted stilbene compounds, while the UV absorption spectra of Schiff bases were affected by both substituents and σ .…”

Boron-containing capsaicinoids

“…Yield: 2.63 g (91%). MP (EtOH) 75.7-78.0 C; 1 47 Synthesis of 1-(3,4-dimethoxyphenyl)-N-(4-tetradecylphenyl) methanimine (13). General procedure 1 was followed using 4tetradecylaniline (1.74 g, 6.02 mmol) and 3,4-dimethoxybenzaldehyde (1.00 g, 6.02 mmol) to give the title compound as a colourless solid.…”

Influences of polarizability effect of alkyl group and homoring competition effect of substituents on the NMR spectra of salen‐type Schiff base

“…It was extensively applied to the QSPR studies [29,[33][34][35] and plays an important role in the study of the chemical shifts. [33,36,37] We use both OH and CH N as reference and express the σ ex CC of the substituent X as σ ex CC X ð Þ OH and σ ex CC X ð Þ CH N by adopting the locating method of substituent X in Section 2.3.2, listed in Table 1.…”