Effects of 4-substituents on electronic spectra of some 2-nitroaniline derivatives

Absorption spectra of some 4-X-2-nitroaniline derivatives (X = NMe 2, NH 2, MeO, PhO, Me, H, COOMe, COOEt, CF 3, SO 2Me) are well correlated by substituent σ p + values or by dual substituent parameter correlations involving σ I and σ R +. It is suggested that this is because the electronic excited...

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Bibliographic Details
Published in:Spectrochimica acta. Part A: Molecular spectroscopy 1984, Vol.40 (7), p.669-673
Main Authors: Yokoyama, Tai, Taft, R.W., Kamlet, Mortimer J.
Format: Article
Language:English
Subjects:
Atomic and molecular physics
Exact sciences and technology
Molecular properties and interactions with photons
Molecular spectra
Physics
Ultraviolet spectra
Visible spectra
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Summary:Absorption spectra of some 4-X-2-nitroaniline derivatives (X = NMe 2, NH 2, MeO, PhO, Me, H, COOMe, COOEt, CF 3, SO 2Me) are well correlated by substituent σ p + values or by dual substituent parameter correlations involving σ I and σ R +. It is suggested that this is because the electronic excited states include important resonance contributions from meta-bridged canonical structures wherein the positive charge on the 1-NH 2 group is delocalized into the 4-(+M) substituent. The results support a suggestion by B rownlee and T opsom that u.v./visible spectral shifts can conform with reasonably precise linear free energy relationships if the substituent being varied is not a part of the chromophore being measured.
ISSN:0584-8539
DOI:10.1016/0584-8539(84)80121-X