Pyromellitic dianhydride

Pyromellitic dianhydride is an organic compound with the formula C₆H₂(C₂O₃)₂. It is the double carboxylic acid anhydride that is used in the preparation of polyimide polymers such as Kapton. It is a white solid.

It is prepared by gas-phase oxidation of 1,2,4,5-tetramethylbenzene (or related tetrasubstituted benzene derivatives). An idealized equation is: