o-phthalodinitrile

Phthalonitrile is an organic compound with the formula C6H4(CN)2, which is an off-white crystal solid at room temperature. It is a derivative of benzene, containing two adjacent nitrile groups. The compound has low solubility in water but is soluble in common organic solvents. The compound is used as a precursor to phthalocyanine and other pigments, fluorescent brighteners, and photographic sensitizers.

== Synthesis == Phthalonitrile is produced industrially in a single-stage continuous process, by the ammoxidation of o-xylene at 480 °C. The reaction is catalyzed by vanadium antimony oxide in a fluidized bed reactor. 330px|Synthesis of phthalonitrile Phthalonitrile was first described in 1896 by Johannes Pinnow. It was noted as a byproduct of the synthesis of ortho-dicyanodiazoamidobenzene via the reaction of ortho-amidobenzonitrile hydrochloride, sodium nitrite, and hydrochloric acid. The first intentional synthesis involved dehydration of phthalamide by boiling in acetic anhydride. Another synthesis of historical interest is the Rosenmund von Braun reaction in which an ortho substituted dihalobenzene is treated with copper(I) cyanide, which results in the halide groups being replaced by cyano groups.