In general, if the atoms that make up the ring contain heteroatoms, such rings become heterocycles, and organic compounds containing heterocycles are called heterocyclic compounds. An article called Reaction of 5-(2-hydroxy-3,5-dinitrophenylazo)-8-hydroxyquinoline N-oxide with copper(II), published in 1979-08-31, which mentions a compound: 1127-45-3, Name is 8-Hydroxyquinoline 1-oxide, Molecular C9H7NO2, Reference of 8-Hydroxyquinoline 1-oxide.
Taking as an example the color reaction between Cu(II) and 5-(2-hydroxy-3,5-dinitrophenylazo-8-hydroxyaquinoline N-oxide (I), the possibility of a new class of anal. reagents based on 8-hydroxyquinoline N-oxide azo compounds was studied. Significant differences were observed when using this class of reagents in complex formation compared to 8-hydroxyquinoline azo derivatives As a result of complex formation I is converted from the azoid form to the quinone-hydrazone form. I reacts with Cu(II) to form a violet-complex in aqueous media and pH 5.9-6.5 with λ maximum at 530 nm. The molar absorptivity of the complex is (9.5 ± 0.1) × 103. The same complex forms in 50% aqueous Me2CO medium at pH 5.5-6.0; λ maximum is at 530 nm with a molar absorptivity of (1.57 ± 0.03) x 104. A rapid extraction-spectrophotometric procedure was developed for Cu determination in Zn alloys and steel by using I. Beer’s law is obeyed up to 1.5 μg Cu/mL. Zn 200; Mn, Ag, and Pb 100; Co 25; and Ni 20; Cl- and NO3- 1000; SO42- 800; and F- 125-fold excess do not interfere; Al, Fe(III), and Cr(III) do. Al and Fe interference can be masked by addition of NaF.
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Reference:
Quinoxaline – Wikipedia,
Quinoxaline | C8H6N2 | ChemSpider