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 Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, ...

, containing two adjacent

nitrile In organic chemistry, a nitrile is any organic compound that has a functional group. The prefix ''cyano-'' is used interchangeably with the term ''nitrile'' in industrial literature. Nitriles are found in many useful compounds, including met ...

groups. The compound has low solubility in water but is soluble in common organic solvents. The compound is used as a precursor to

phthalocyanine Phthalocyanine () is a large, aromatic, macrocyclic, organic compound with the formula and is of theoretical or specialized interest in chemical dyes and photoelectricity. It is composed of four isoindole units linked by a ring of nitrogen atom ...

and other pigments, fluorescent brighteners, and photographic sensitizers.

Synthesis

Phthalonitrile is produced industrially in a single-stage continuous process, by the

ammoxidation In organic chemistry, ammoxidation is a process for the production of nitriles () using ammonia () and oxygen (). It is sometimes called the SOHIO process, acknowledging that ammoxidation was developed at Standard Oil of Ohio. The usual substrat ...

of ''o''-xylene at 480 °C. The reaction is catalyzed by vanadium oxide-antimony-oxide in a

fluidized bed reactor A fluidized bed reactor (FBR) is a type of reactor device that can be used to carry out a variety of multiphase chemical reactions. In this type of reactor, a fluid (gas or liquid) is passed through a solid granular material (usually a catalyst ...

.Lorz, Peter M. "Phthalic Acid and Derivatives" in Ulmanns Encyclopedia of Industrial Chemistry. Wiley-VCH: Weinheim, 2002. . : Synthesis Phthalonitrile Ammonoxidation

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-amido

benzonitrile Benzonitrile is the chemical compound with the formula , abbreviated PhCN. This aromatic organic compound is a colorless liquid with a sweet bitter almond odour. It is mainly used as a precursor to the resin benzoguanamine. Production It is pr ...

hydrochloride,

sodium nitrite Sodium nitrite is an inorganic compound with the chemical formula NaNO2. It is a white to slightly yellowish crystalline powder that is very soluble in water and is hygroscopic. From an industrial perspective, it is the most important nitrite ...

, and

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...

. The first intentional synthesis involved dehydration of phthalamide by boiling in

acetic anhydride Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula (CH3CO)2O. Commonly abbreviated Ac2O, it is the simplest isolable anhydride of a carboxylic acid and is widely used as a reagent in organic synthesis. It is a col ...

. 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.

Applications

Phthalonitrile is the precursor to

pigments, a very common organic pigment. Such pigments are generated through the reaction of phthalonitrile with various metal precursors. The reaction is carried out in a solvent at around 180 °C.. : Synthesis Metallo Phthalocyanine

Ammonolysis of phthalonitrile gives to diimino

isoindoline Isoindoline is a heterocyclic organic compound with the molecular formula C8H9N. The parent compound has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered nitrogen-containing ring. The compound's structure is ...

. This intermediate condensation with active methylene compounds to give commercially important

pigment yellow 185 Pigment yellow 185 is an organic compound that is used as a green yellow pigment and optical brightener. It is classified as a derivative of isoindoline. This yellow green compound is prepared by addition of ammonia to ''o''- phthalonitrile to ...

and

pigment yellow 139 Pigment yellow 139 is an organic compound that is used as a yellow-orange pigment. It is classified as a derivative of isoindoline. This yellow-orange solid is virtually insoluble in most solvents.K. Hunger. W. Herbst "Pigments, Organic" in ''Ull ...

References

{{Authority control Benzonitriles