Illustrated Glossary of Organic Chemistry

Terephthalic acid: A dicarboxylic acid consisting of a benzene ring with the carboxylic acid groups in a 1,4 (para) arrangement. IUPAC name benzene-1,4-dicarboxylic acid. The carboxylic acid monomer which is copolymerized with ethylene glycol to form the common plastic polyethylene terephthalate (PET).

Molecular structure of terephthalic acid.