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Phthalonitrile is a crystalline powder having a faint grayish yellow color and a slighty aromatic odor, similar to benzonitrile. Phthalonitrile was first described in 1896 when it was isolated during the diazotization of 2-aminobenzonitrile. The compound is sparingly soluble in water (ca. 1 g/L) and soluble in acetone, nitrobenzene, and benzonitrile. It cannot be distilled and polymerizes if heated above the melting point. It is not explosive and is difficult to ignite, but the dust can explode.

Phthalonitrile is used as a starting material for producing phthalocyanine pigments (→ Phthalocyanines), fluorescent brightners, and photographic sensitizers.

Phthalonitrile can be produced from phthalic acid, phthalic anhydride, phthalamide, or phthalimide by reaction with ammonia and elimination of water at 300–500°C in the gas phase in the presence of a catalyst.

In a single-stage continuous process, o-xylene is converted to phthalonitrile by reaction with ammonia and oxygen in the gas phase in a fluidized-bed reactor. Generally, metal oxide mixtures containing vanadium, antimony, chromium, and molybdenum, with further active components such as iron, tungsten, and alkali-metal oxides, on an alumina or silica support are used as catalysts.

The route from o-phthalodinitrile can be represented 4C8H4N2 +M → MPc, where M is a bivalent metal, metal halide, metal alcoholate, or an equivalent amount of metal of valence other than two in a 4:1 molar ratio.

Notclassified

Crystallise the nitrile from EtOH, toluene or *benzene. It has also been distilled under high vacuum. It is steam volatile. [Beilstein 9 H 815, 9 II 602, 9 III 4199, 9 IV 3268.]