A benzene polycarboxylic acid is a derivative of benzene with two or more carboxylic acid functional groups. These compounds have the chemical formula C6+nH6O2n or C6H6−n(COOH)n.
Benzenedicarboxylic acid, n = 2 {\displaystyle n=2} , three isomers: Isophthalic acid (1,2-benzenedicarboxylic acid) Phthalic acid (1,3-benzenedicarboxylic acid) Terephthalic acid (1,4-benzenedicarboxylic acid) Benzenetricarboxylic acid, n = 3 {\displaystyle n=3} , three isomers: Hemimellitic acid (1,2,3-benzenetricarboxylic acid) Trimellitic acid (1,2,4-benzenetricarboxylic acid) Trimesic acid (1,3,5-benzenetricarboxylic acid) Benzenetetracarboxylic acid, n = 4 {\displaystyle n=4} , three isomers: 1,2,3,4-benzenetetracarboxylic acid 1,2,3,5-benzenetetracarboxylic acid Pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid) Benzenepentacarboxylic acid, n = 5 {\displaystyle n=5}
Mellitic acid (benzenehexacarboxylic acid), n = 6 {\displaystyle n=6}