C6H4COOH2

C6H4COOH2 is a condensed way to describe benzenedicarboxylic acids, a family of compounds consisting of a benzene ring bearing two carboxyl groups (COOH). The exact structure depends on the positions of the carboxyl groups, giving three common isomers: ortho-benzenedicarboxylic acid (1,2-), isophthalic acid (1,3-), and terephthalic acid (1,4-). All three share the same molecular formula, C8H6O4, but differ in physical properties and reactivity due to their substituent arrangement.

Industrial production of these acids generally involves oxidation of the corresponding xylene isomers or related benzenoid precursors. For example, terephthalic acid is produced by oxidizing p-xylene, while phthalic and isophthalic acids arise from oxidation of o- and m-xylene, respectively. The acids can also be accessed via hydrolysis of esters or other oxidation routes used in larger-scale chemical manufacturing.

Applications and significance include their use as key monomers in the production of polyesters. Notably, terephthalic acid and its dimethyl ester are central precursors to polyethylene terephthalate (PET), a widely used polymer for fibers and plastic bottles. Isophthalic and phthalic acids are also employed in various polyesters, resins, and specialty chemicals, including dyes and pigments, crosslinkers, and plasticizers.

Physicochemical properties vary by isomer but, in general, these compounds are solid at room temperature with high melting points and limited water solubility. They are typically handled as solids or converted to more reactive derivatives (e.g., esters or anhydrides) for processing.

Safety considerations include irritation potential on skin and eyes; standard laboratory and industrial hygiene practices apply to handling and storage.