A quinoxaline, also called a benzopyrazine, in organic chemistry, is a heterocyclic compound containing a ring complex made up of a benzene ring and a pyrazine ring. It is isomeric with other naphthyridines including quinazoline, phthalazine and cinnoline.[3] It is a colorless oil that melts just above room temperature. Although quinoxaline itself is mainly of academic interest, quinoxaline derivatives are used as dyes, pharmaceuticals (such as varenicline), and antibiotics such as olaquindox, carbadox, echinomycin, levomycin and actinoleutin.
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Names | |||
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Preferred IUPAC name
Quinoxaline[1] | |||
Other names
Benzo[b]pyrazine, Benzopyrazine, Benzoparadiazine, 1,4-Benzodiazine, Phenopiazine, Phenpiazine, Quinazine, Chinoxalin
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Identifiers | |||
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3D model (JSmol)
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ChEBI |
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ChEMBL |
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ChemSpider |
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ECHA InfoCard | 100.001.862 | ||
EC Number |
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KEGG |
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PubChem CID
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UNII |
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CompTox Dashboard (EPA)
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Properties | |||
C8H6N2 | |||
Molar mass | 130.150 g·mol−1 | ||
Melting point | 29-32 °C | ||
Boiling point | 220 to 223 °C (428 to 433 °F; 493 to 496 K) | ||
Acidity (pKa) | 0.60[2] | ||
Hazards | |||
GHS labelling: | |||
Warning | |||
H315, H319, H335 | |||
P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501 | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references
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They can be formed by condensing ortho-diamines with 1,2-diketones. The parent substance of the group, quinoxaline, results when glyoxal is condensed with 1,2-diaminobenzene.[4] Substituted derivatives arise when α-ketonic acids, α-chlorketones, α-aldehyde alcohols and α-ketone alcohols are used in place of diketones.[3] Quinoxaline and its analogues may also be formed by reduction of amino acids substituted 1,5-difluoro-2,4-dinitrobenzene (DFDNB):[5]
One study[6] used 2-iodoxybenzoic acid (IBX) as a catalyst in the reaction of benzil with 1,2-diaminobenzene:
The antitumoral properties of quinoxaline compounds have been of interest.[7] Recently, quinoxaline and its analogs have been investigated as the catalyst's ligands.[8]