Phthalic Anhydride(redirected from Gibbs phthalic anhydride process)
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phthalic anhydride[′thal·ik an′hī‚drīd]
(also acid phthalic anhydride), a colorless crystalline compound, with a melting point of 130.8°C and a boiling point of 284.5°C. It is practically insoluble in water and moderately soluble in organic solvents.
Phthalic anhydride is an important starting product in the manufacture of various phthalic-acid derivatives, including esters, phthalimide, and phthalonitrile. The condensation of phthalic anhydride with phenols is used to obtain dyes, such as phenolphthalein. Much of the phthalic anhydride produced is used in the manufacture of glyptal, penta resins, intermediate products, dyes—derivatives of fluorescein, rhodamine, and anthra-quinone—and drugs, such as the anticoagulants Ftalazol (phthalylsulfathiazole) and Fenilin (phenindione).
Phthalic anhydride is prepared by the catalytic oxidation of naphthalene or ortho-xylene by air in the gaseous phase.