title: Benzenedicarboxylic acid
text: # Benzenedicarboxylic acid
  
  Benzenedicarboxylic acid is a group of chemical compounds which are dicarboxylic derivatives of benzene. Benzenedicarboxylic acid comes in three isomers:
  
  * Phthalic acid (1,2-benzenedicarboxylic acid)
  * Isophthalic acid (1,3-benzenedicarboxylic acid)
  * Terephthalic acid (1,4-benzenedicarboxylic acid)
  
  | Common Name | Phthalic acid | Isophthalic acid | Terephthalic acid |
  | - | - | - | - |
  | Systematic Name | 1,2-benzenedicarboxylic acid | 1,3-benzenedicarboxylic acid | 1,4-benzenedicarboxylic acid |
  | Structural Formula | | | |
  | CAS Registry Number | 88-99-3 | 121-91-5 | 100-21-0 |
  
  All isomers share the molecular weight 166.13 g/mol and the chemical formula $C_8H_6O_4.$
  
  