Phthalic Anhydride and Its Chemical Properties

1. Phthalic anhydride meaning

The phthalic anhydride meaning: phthalic anhydride is also known as the phthalic acid anhydride; 1,2-benzenedicarboxylic acid an-hydride; 1,2-benzenedicarboxylic anhydride; 1,3-isobenzofurandione; 1,3-phthalandione, etc. The molecular formula is C8H4O3 and abbreviation is PA. There are many physical properties of phthalic anhydride. Phthalic anhydride is a cyclic acid anhydride formed by the dehydration of phthalic acid molecule. It is a white powder or scaly crystalline solid with a specific gravity of 1.527 (4°C). The flash point of pure phthalic anhydride is 152°C, phthalic anhydride melting point is 130.8°C, and the boiling point is 284.5°C; It is easy to have sublimation, slightly soluble in cold water, hydrolyzed to phthalic acid in hot water, easily soluble in ethanol, benzene and pyridine, and slightly soluble in ether; This product is moderately toxic and can cause asthma: It has been reported that with long-term inhalation, it may bring damage to the reproductive, nervous, liver and kidney systems, as well as irritation to the skin, mucous membranes, especially the cornea. Therefore, necessary protection is needed when touching the product to ensure personal safety.

Phthalic anhydride is a white solid material, with common phthalic anhydride applications in the chemical industry, which is especially used for the manufacture of plasticizers. Both dibutyl phthalate and dioctyl phthalate are important plasticizers. Phthalic anhydride and polyols (such as glycerol, pentaerythritol) are polycondensed to form polyarylate resin, which is used in the paint industry; If it is polycondensed with ethylene glycol and unsaturated acid, it generates unsaturated polyester resin, which can be used to make insulating paint and glass fiber reinforced plastic. Phthalic anhydride is also a raw material for the synthesis of benzoic acid and terephthalic acid, and is also used in the synthesis of medicines. Phthalic anhydride can produce hydrolysis, alcoholysis and ammonolysis reactions, and can react with aromatic hydrocarbons to synthesize anthraquinone derivatives. Phthalic anhydride is industrially prepared by the vapor-phase oxidation of naphthalene and air at 350-360°C under the catalysis of the vanadium pentoxide. It can also be prepared by the oxidation of o-xylene with air. Due to phthalic anhydride properties, it has a wide range of applications.

2. The chemical properties of phthalic anhydride

Phthalic anhydride can produce hydrolysis, alcoholysis and ammonolysis reactions, and react with aromatic hydrocarbons to synthesize anthraquinone derivatives. Phthalic anhydride is industrially prepared by the vapor-phase oxidation of naphthalene and air at 350-360°C under the catalysis of vanadium pentoxide. It can also be prepared by the oxidation of o-xylene with air. Phthalic anhydride can be used to take the place of phthalic acid and mainly react with monohydric alcohols to form esters, such as dibutyl phthalate and dioctyl phthalate.

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