Phthalazines
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[[Image:Phthalazin - Phthalazine.svg|thumb|Phthalazine.]]
'''Phthalazines''', also called benzo-orthodiazines or benzopyridazines, are a group of [[heterocyclic]] compounds containing a ring complex. They are [[isomeric]] with the [[cinnoline]]s. The parent substance of the group, phthalazine, C<sub>8</sub>H<sub>6</sub>N<sub>2</sub>, is best obtained from the condensation of w-tetrabromorthoxylene with [[hydrazine]], or by the [[Redox|reduction]] of chlorphthalazine with [[phosphorus]] and [[hydroiodic acid]]. It possesses [[base (chemistry)|basic]] properties and forms addition products with [[alkyl iodide]]s. On oxidation with [[alkaline]] [[potassium permanganate]] it yields [[pyridazine]] [[dicarboxylic acid]]. [[Zinc]] and [[hydrochloric acid]] decompose it with formation of orthoxylylene diamine. The keto-hydro derivative phthalazone (C<sub>8</sub>H<sub>6</sub>ON<sub>2</sub>), is obtained by condensing hydrazine with orthophthalaldehydoacid. On treatment with [[phosphorus oxychloride]] it yields a chlorphthalazine, which with [[zinc]] and [[hydrochloric acid]] gives isoindole (C<sub>8</sub>H<sub>7</sub>N), and with [[tin]] and hydrochloric acid, phthalimidine (C<sub>8</sub>H<sub>7</sub>ON), the second [[nitrogen]] [[atom]] being eliminated as [[ammonia]].
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[[Category:Heterocyclic compounds]]
[[Category:Pyridazines]]