Electrochemical behavior of quinoxalin-2-one derivatives at mercury electrodes and its analytical use.
Derivatives of quinoxalin-2-one are interesting compounds with potential pharmacological activity. From this point of view, understanding of their electrochemical behavior is of great importance. In the present paper, a mechanism of electrochemical reduction of quinoxalin-2-one derivatives at mercury dropping electrode was proposed. Pyrazine ring was found to be the main electroactive center undergoing a pH-dependent two-electron reduction process. The molecule protonization of nitrogen in the position 4 precedes the electron acceptance forming a semiquinone radical intermediate which is relatively stable in acidic solutions. Its further reduction is manifested by separated current signal. A positive mesomeric effect of the nonprotonized amino group in the position 7 of the derivative III accelerates the semiquinone reduction yielding a single current wave. The suggested reaction mechanism was verified by means of direct current polarography, differential pulse, cyclic and elimination voltammetry, and coulometry with subsequent GC/MS analysis. The understanding of the mechanism was applied in developing of analytical method for the determination of the studied compounds.
Department of Analytical Chemistry, Faculty of Science, Palacky University in Olomouc, 17 Listopadu 12, 77146 Olomouc, Czech Republic.
Milan
M
Zimpl
Jana
J
Skopalova
David
D
Jirovsky
Petr
P
Bartak
Tomas
T
Navratil
Jana
J
Sedonikova
Milan
M
Kotoucek
D055664:Electrochemical Techniques; D004566:Electrodes; D008401:Gas Chromatography-Mass Spectrometry; D008628:Mercury / Q000737:chemistry*; D011810:Quinoxalines / Q000737:chemistry*
D011810:Quinoxalines; D008628:Mercury