Phthalazine, which is also known as benzo-orthodiazine or benzopyridazine, is an organic compound with a heterocyclic structure and the molecular formula C8H6N2. It shares isomeric properties with other naphthyridines, such as quinoxaline, cinnoline, and quinazoline.Similar to cinnolines, phthalazines were commonly synthesized by condensing compounds that contain hydrazine with those that contain carbonyl groups.Similar to pyridazines, the synthesis of phthalazines, which are another class of benzopyridazines, was predominantly achieved by condensing hydrazines with carbonyl-containing compounds, commonly phthalate derivatives.