What is "diazine"

n. (context organic compound English) Any six-membered aromatic heterocycle containing four carbon atoms, two nitrogen atoms and three double bonds

Diazine refers to a group of organic compounds having the molecular formula CHN. Each contains a benzene ring in which two of the C-H fragments have been replaced by isolobal nitrogen. There are three isomers:

• pyrazine (1,4-diazine) image:pyrazine simple structure.svg
• pyrimidine (1,3-diazine) image:Pyrimidin.svg
• pyridazine (1,2-diazine) image:pyridazine simple structure.svg