Pyromellitic dianhydride
Pyromellitic dianhydride is an organic compound with the formula C6H22. It is the double carboxylic acid anhydride that is used in the preparation of polyimide polymers such as Kapton. It is a white solid.Preparation
It is prepared by gas-phase oxidation of 1,2,4,5-tetramethylbenzene. An idealized equation is:
In the laboratory, it can be prepared by dehydration of pyromellitic acid using acetic anhydride.Reactions
PMDA is an electron-acceptor, forming a variety of charge-transfer complexes. It reacts with amines to diimides, C6H22 which also have acceptor properties.Safety
Some evidence suggests that PMDA causes occupational asthma.
