Isophthalic acid is an organic compound with the formulaC 6 H 4 (CO 2 H) 2 . This colourless solid
is an isomer of phthalic acid and terephthalic acid. The main industrial uses of purified
isophthalic acid are to produce polyethylene terephthalate (PET) resin and to
produce unsaturated polyester resin (UPR) and other types of coating resins.
Isophthalic acid is produced on the billion kilogram per year scale by oxidizing meta-
xylene using oxygen. The process employs a cobalt-manganese catalyst. The world's largest
producer of isophthalic acid is Lotte Chemical Corporation.
In the laboratory, chromic acid can be used as the oxidant. It also arises by fusing potassium
meta-sulfobenzoate, or meta-bromobenzoate with potassium formate (terephthalic acid is also
formed in the last case).
The barium salt, as its hexahydrate, is very soluble in water (a distinction between phthalic
and terephthalic acids). Uvitic acid, 5-methylisophthalic acid, is obtained by
oxidizing mesitylene or by condensing pyroracemic acid with baryta water.
Aromatic dicarboxylic acids are used as precursors (in form of acyl chlorides) to
commercially important polymers, e.g. the fire-resistant material Nomex. Mixed with
terephthalic acid, isophthalic acid is used in the production of PET resins for drink plastic
bottles and food packaging. The high-performance polymer polybenzimidazole is produced
from isophthalic acid. Also, the acid is used as an important input to produce insulation