C6H4CO2H2

C6H4CO2H2 is the condensed formula for benzene-1,4-dicarboxylic acid and the related benzene-1,2- and benzene-1,3-dicarboxylic acids. The three isomers share the molecular formula C8H6O4. In common usage, the para isomer is called terephthalic acid (benzene-1,4-dicarboxylic acid), the meta is isophthalic acid, and the ortho is phthalic acid.

Chemical features include a benzene ring bearing two carboxyl groups. The carboxyl groups confer acidity and enable esterification, making these compounds important precursors to polyesters and other polymers. The isomers differ in the relative positions of the carboxyl groups, which affects properties and applications.

Production and uses: industrial terephthalic acid is primarily produced by oxidation of p-xylene with air in the presence of catalysts. It is a major monomer for polyethylene terephthalate (PET) plastics and related polyesters used in fibers, bottles, and films, as well as for resins and coatings. Isophthalic and phthalic acids are used similarly in specialty polymers and resins, and as precursors for various chemical products.

Physical properties: it is a white, crystalline solid with limited water solubility under ambient conditions. It is stable under ordinary conditions but decomposes when exposed to strong heating. It behaves as a dibasic aromatic carboxylic acid and forms a range of derivatives, such as diesters and dianhydrides.

Safety: handled as a chemical for industrial use; dust may irritate skin and eyes; avoid inhalation of dust and contact with skin or eyes. Use appropriate protective equipment and follow standard safety practices.