Structure vs. reactivity in quinoxalinecarboxylic acids and esters was written by Gum, Wilson F. Jr.;Joullie, Madeleine M.. And the article was included in Journal of Organic Chemistry in 1965.Formula: C7H8N2O2 This article mentions the following:
In an attempt to establish a correlation between the calculated electron densities in an unperturbed quinoxaline nucleus and the reactivities of its derivatives, the pKA values of 2-, 2,3-, 6-, 5-, and 2,3-dimethyl-5-quinoxalinecarboxylic acids (I, II, III, IV, V) were measured. The carbonyl frequencies of the corresponding Me and Et esters (VI-XII) were determined by ir spectroscopy and tabulated together with those of Et and Me pyra-zinecarboxylate. Good correlation seemed to exist between pKA values of the acids I-V and the electron d. calculated by Longuet-Higgins and Coulson (CA 41, 4978b) but only poor correlation with those reported by Basur and Bhattacharya (CA 52, 864i and by Pullman (CA 41, 197b). The split carbonyl bands observed for the esters VI-XII should be ascribed to conformational isomerism rather than to Fermi resonance. Relative pKA values of I-V were predictable from electron densities of the unsubstituted quinoxaline ring even though the carboxylate anions formed during the determination must perturb the ring densities. The effect is apparently small in relation to the perturbed electron d. caused by the ring N atoms in the unsubstituted quinoxaline nucleus. In the experiment, the researchers used many compounds, for example, Ethyl pyrazine-2-carboxylate (cas: 6924-68-1Formula: C7H8N2O2).
Ethyl pyrazine-2-carboxylate (cas: 6924-68-1) belongs to pyrazine derivatives. Pyrazines are part of several biologically active polycyclic compounds; examples are quinoxalines, phenazines; and the bio-luminescent natural products pteridines, flavins, and their derivatives. Pyrazine and a variety of alkylpyrazines are flavor and aroma compounds found in baked and roasted goods. Tetramethylpyrazine (also known as ligustrazine) is reported to scavenge superoxide anion and decrease nitric oxide production in human Granulocytes.Formula: C7H8N2O2