Phthalic anhydride is an organic compound with the chemical formula C₈H₄O₃. It is the anhydride of phthalic acid and is commonly used in the production of plasticizers, dyes, and pigments.

Key Properties

Chemical Formula: C₈H₄O₃
Molar Mass: 148.1 g/mol
Appearance: White flakes or crystalline powder
Odor: Characteristic, acrid smell
Melting Point: 131.6°C (268.9°F)
Boiling Point: 295°C (563°F)
Solubility: Slightly soluble in water, soluble in organic solvents like ethanol and ether

Synthesis

Phthalic anhydride is primarily produced by the oxidation of o-xylene or naphthalene using vanadium pentoxide (V₂O₅) as a catalyst. The modern industrial process involves gas-phase oxidation at high temperatures.

Applications

Plasticizers: Used to produce phthalate esters, which are added to plastics to increase flexibility.
Dyes and Pigments: Serves as a precursor for the synthesis of various dyes and pigments.
Resins and Coatings: Utilized in the production of alkyd resins and coatings.
Pharmaceuticals: Acts as an intermediate in the synthesis of certain pharmaceuticals.