Abstract

EL-ATTAR, Mona A.; ISMAIL, Iqbal M.  and  GHONEIM, Mohamed M.. Synthesis, electrochemical, spectrophotometric and potentiometric studies of two azo-compounds derived from 4-amino-2-methylquinoline in ethanolic-aqueous buffered solutions. J. Braz. Chem. Soc. [online]. 2012, vol.23, n.8, pp. 1523-1535.  Epub Aug 09, 2012. ISSN 0103-5053.  http://dx.doi.org/10.1590/S0103-50532012005000013.

Two azo-compounds, 2-methyl-4-(5-amino-2-hydroxy-phenylazo)-quinoline (2) and 2-methyl-4-(2-hydroxy-5-nitrophenylazo)-quinoline, derived from 4-amino-2-methylquinoline were synthesized. Their chemical structures were characterized and confirmed by means of elemental chemical analysis, infrared (IR) spectroscopy, ¹H nuclear magnetic resonance (NMR) and mass spectrometry (MS). The electrochemical behavior of the starting compound (4-amino-2-methylquinoline) and of the two synthesized azo-derivatives was studied at the mercury electrode in the B-R universal buffer at various pH values (2-11.5) containing 40% (v/v) ethanol using dc-polarography, cyclic voltammetry and controlled-potential coulometry. Their electrode reaction pathways were elucidated and discussed. The dissociation constants (pKa) of the examined compounds, stability constants and stoichiometry of their complexes in solution with some transition metal ions (Co(II), Ni(II), Cu(II), La(III) and UO₂²⁺) were determined.

Keywords : 4-amino-2-methylquinoline; azo-derivatives; voltammetry; spectrophotometry; potentiometry.