Pyridine gives origin to: pyridazine or ortho-diazine, pyrimidine or metadiazine, pyrazine or para-diazine, osotriazine, unsymmetrical triazine, symmetrical triazine, osotetrazone and tetrazine.
Their alkyl derivatives readily oxidize to pyrazine carboxylic acids.
Pyrazine, C4H4N2, crystallizes from water in prisms, which have a heliotrope odour.
It melts at 55° C. and boils at 115° C. It may also be obtained by elimination of carbon dioxide from the pyrazine dicarboxylic acid formed when quinoxaline is oxidized with alkaline potassium permanganate (S.
And III., pyrazine being I.: HC N CH HC NH CH HC N CH2 H2C NH CH2 HC N CH2 H2C NH H2 I (Pyrazine) II (1.4 dihydro) III (2.3 dihydro) IV (Piperazine).
Above), also known as diethylene diamine, may be prepared by reducing pyrazine, or, better, by combining aniline and ethylene bromide to form diphenyl diethylene diamine, the dinitroso compound of which hydrolyses to para-dinitrosophenol and pipera zine.