phthalazine
/ˈ(f)θaləziːn/Chemistry
noun
An aromatic heterocyclic base, C8H6N2, whose molecule resembles that of naphthalene with the carbon atoms at positions 2 and 3 replaced by nitrogen; 2,3-benzodiazine, 2,3-diazanaphthalene.
Origin
Late 19th century; earliest use found in Journal of the Chemical Society. From phthal- + azine, after German Phtalazin.