erephthalic acid is an organic compound with formula C₆H₄₂. This white solid is a commodity chemical, used principally as a precursor to the polyester PET, used to make clothing and plastic bottles. Several million tons are produced annually. The common name is derived from the turpentine-producing tree Pistacia terebinthus and phthalic acid. Terephthalic acid is also used in the production of PBT plastic.