Structure dependent prototropy in 4-hydroxy-3-formylideneamino-1-methyl/phenylquinolin-2-ones

The electronic absorption spectra of 4-hydroxy-3-formyl quinolin-2-ones and their Schiff bases were investigated in various solvents of varying polarity. The three aromatic transitions of napthalene in quinolin-2-one are shifted to longer wavelength on their transformation to anils. Electron-donatin...

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Bibliographic Details
Published in:Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2009-09, Vol.73 (5), p.916-921
Main Authors: Sheshashena Reddy, T., Rameshwar, N., Bhudevi, B., Reddy, A. Ram
Format: Article
Language:English
Subjects:
4-Hydroxy-quinolin-2-one
Anil
Electronic absorption spectra
Enolimine
Ketoamine
Prototropy
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Summary:The electronic absorption spectra of 4-hydroxy-3-formyl quinolin-2-ones and their Schiff bases were investigated in various solvents of varying polarity. The three aromatic transitions of napthalene in quinolin-2-one are shifted to longer wavelength on their transformation to anils. Electron-donating group in the anils lead to enolimine form, while electron-withdrawing group leads to an equilibrium mixture of enolimine and ketoamine forms and the Schiff base derived from alkyl amine exist in ketoamine form. The prototropic interconversion of enolimine and ketoimine forms in the anils with the electron-withdrawing substituted anils is further supported by proton NMR studies. The spectral shifts are solvent dependent. Dipolar aprotic solvents bring bathochromic shift while polar protic solvents cause blue shift in the longer wavelength absorption maxima. In the case of Schiff bases substituted by electron-donating group the bathochromic shift is directly related to the polarity of the solvents.
ISSN:1386-1425
DOI:10.1016/j.saa.2009.04.019