Phthalic anhydride ,PA, C8H4O3
Phthalic anhydride is an organic compound with the chemical formula C8H4O3. It is a cyclic anhydride formed by the intramolecular dehydration of phthalic acid. It appears as a white crystalline powder and is insoluble in cold water but slightly soluble in hot water and ether. It is soluble in ethanol, pyridine, benzene, carbon disulfide, etc. It is an important raw material in the organic chemical industry and serves as a key intermediate for the production of phthalate plasticizers, coatings, saccharin, dyes, and various organic compounds.
Its molecular weight is 148.12, melting point is 131.1l ℃, boiling point is 284.5 ℃, flash point is 151 ℃ (closed) and 165 ℃ (open), spontaneous ignition point is 584 ℃and density (solid) is 1.527g/cm3.
Phthalic anhydride can undergo hydrolysis, alcoholysis and amylization reactions. When reacting with aromatic hydrocarbons, it can synthesize anthraquinone derivatives. Phthalic anhydride can be used as a substitute for phthalic acid, mainly forming esters with monohydric alcohols, such as phthalic acid dibutyl ester and phthalic acid dioctyl ester.