ftaalzuuranhydride

ftaalzuuranhydride, or orhto-phthalic anhydride, is the cyclic anhydride of phthalic acid (benzene-1,2-dicarboxylic acid). Its chemical formula is C8H4O3, and it appears as a white solid. It is sparingly soluble in water and more soluble in many organic solvents. As an reactive carboxylic anhydride, it hydrolyzes in the presence of moisture to phthalic acid and can undergo esterification with alcohols to give phthalate esters or react with amines to form amide or imide derivatives.

Structure and properties

Phthalic anhydride is derived from a o-substituted benzenedicarboxylic framework. The molecule consists of a benzene ring fused to a five-membered anhydride ring containing two carbonyl groups. This arrangement makes it a versatile acylating agent in organic synthesis and a stepping stone to various phthalate derivatives used in plastics and coatings.

Production

Industrial production of ftaalzuuranhydride is dominated by catalytic oxidation of o-xylene or, less commonly, of naphthalene, using air and a vanadium oxide–based catalyst at elevated temperature. The oxidation mixture is processed to isolate phthalic anhydride, with purification by distillation and crystallization.

Applications

The compound is a key intermediate in the manufacture of phthalate plasticizers (for example esters with alcohols), alkyd resins, and unsaturated polyester resins. It is also used as a precursor for phthalic derivatives in dyes, pigments, and specialty chemicals. Its reactivity as an anhydride enables it to introduce the phthaloyl group into larger molecules.

Safety

ftaalzuuranhydride is an irritant to skin, eyes, and the respiratory tract. Dust or vapors can cause irritation; appropriate handling includes use of fume hoods, gloves, and eye protection. It can react with moisture to form phthalic acid, and releases should be managed to avoid exposure and environmental release.