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Ethylenetetracarboxylic dianhydride is a chemical compound with formula C
6O
6, that can be seen as the twofold anhydride of ethylenetetracarboxylic acid C
6H
4O
8. Its molecular backbone consists of two five-atom maleic anhydride rings, each containing one oxygen atom and four carbon atoms, sharing a pair of carbons. It is one of the oxides of carbon. It is a pale yellow oily liquid, soluble in dichloromethane and trichloromethane.
The compound and its reactions were studied in 1967 by Sauer, Schröder and others. Synthesis of the compound by pyrolysis of ethylenetetracarboxilic acid was reported in 1981 by Patterson and others.
The compound was also obtained in 2009 by Taherpour, by microwave pyrolysis of solid Meldrum's acid. Two molecules of the acid are believed to dimerize via an alkene linkage. The meldrum's-acid rings open via hydrolysis to form ethylenetetracarboxylic acid, and then the carboxylic acid units recyclize with different partners to form the dianhydride.