Phthalic anhydride is a colorless, easily subliming crystalline compound. It is boundedly soluble in formic and acetic acid, carbon disulfide, pyridine and cold water. It is hydrolyzed by hot water, forming ortho-phthalic acid. It reacts with monoatomic alcohols in the presence of mineral acids to give mono- and diesters. Reaction with polyatomic alcohols results in polyesters (alkyd resins). Phthalic anhydride undergoes catalytic condensation with benzene to form anthraquinone. Interaction with phenols is an commercial method for dyes and pigments preparation (e.g. phenolphthaleine).
Production.
Phthalic anhydride is produced by vapour-phase catalytic oxidation of ortho-xylene or naphthalene with oxygen at 350-400°C in the presence of V2O5/TiO2 or V2O5/K2SO4.
Uses.
Phthalic anhydride is used:
in alkyd resins production;
for plasticizers preparation (phthalic acid diesters);
in dyes and pigments syntheses (rhodamine, anthraquinone derivatives);
in making of tetrachlorophthalic anhydride, polyetherimide resins, polyester polyols, unsaturated polyester resins, isatoic anhydride and other chemical products;
as an intermediate in preparation of pharmaceuticals;
