Phthalic anhydride

Phthalic anhydride is the anhydride of phthalic acid. This colorless solid is an important industrial chemical, especially for the large–scale production of plasticizers for plastics. It is presently obtained by catalytic oxidation of ortho–xylene or naphthalene. Phthalic anhydride can also be prepared from phthalic acid.


It is a white, crystalline, slightly water-soluble solid, C8H4O3, used chiefly in the manufacture of dyes, alkyd resins, and plasticizers.

Phthalic anhydride(CAS.NO:85-44-9) is a versatile intermediate in organic chemistry,It is used in the production of unsaturated polyester resins and alkyd resins used in the coatings industry.  in part because it is bifunctional and readily available. The primary use of phthalic anhydride (PA) is as a chemical intermediate in the production of plasticizers from polyvinyl chloride (PVC).
Phthalic anhydride is a versatile intermediate in organic chemistry, in part because it is bifunctional and cheaply available. It undergoes hydrolysis and alcoholysis. Hydrolysis by hot water forms ortho-phthalic acid. This process is reversible: Phthalic anhydride re-forms upon heating the acid above 180 °C. Hydrolysis of anhydrides is not typically a reversible process. However, phthalic acid is easily dehydrated to form phthalic anhydride due to the creation of a thermodynamically favorable 5-membered ring.

Phthalic anhydride reacted with cellulose acetate forms cellulose acetate phthalate (CAP), a common enteric coating excipient that has also been shown to have antiviral activity.Phthalic anhydride is a degradation product of CAP.

Phthalic anhydride is the catalyst for oxidation and dehydrogenation.


It's colourless, aromatic chemical solid, which forms needle shaped crystals. The chemical starts to solve at a temperature of 131°degrees and changes over to gas state at 256° degrees. The majority of phthalic anhydride is used for the production and plasticizers, especially PVC. As an important synthetic resign resource the chemical bond is utilized for the surface coating of wood, for the manufacture of copper phthalocyanine in the beta crystalline form and synthetic resin. The chemical bond of phthalic anhydride is also only an important chemical component for producing colorants. Colour pigments produced with phthalic anhydride are remanufactured in dispersions, artistic colour or in finish.