Phthalazine
# Phthalazine

Phthalazine, also called benzo-orthodiazine or benzopyridazine, is a heterocyclic organic compound with the molecular formula $C_8H_6N_2.$ It is isomeric with other naphthyridines including quinoxaline, cinnoline and quinazoline.

## Synthesis

Phthalazine can be obtained by the condensation of w-tetrabromorthoxylene with hydrazine, or by the reduction of chlorphthalazine with phosphorus and hydroiodic acid.

## Properties

It possesses basic properties and forms addition products with alkyl iodides.

## Reactions

Upon 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 $(C_8H_6ON_2),$ is obtained by condensing hydrazine with orthophthalaldehydoacid. On treatment with phosphorus oxychloride, it yields a chlorphthalazine, which with zinc and hydrochloric acid gives isoindole $(C_8H_7N),$ and with tin and hydrochloric acid, phthalimidine $(C_8H_7ON),$ the second nitrogen atom being eliminated as ammonia.

