Ethylenetetracarboxylic dianhydride

Ethylenetetracarboxylic dianhydride is a chemical compound with formula C
, that can be seen as the twofold anhydride of ethylenetetracarboxylic acid C
. It has a bicyclic molecular structure consisting of two maleic anhydride rings fused by their respective alkene units. It is a pale yellow oily liquid, soluble in dichloromethane and chloroform.[1]

The compound and its reactions were first reported in 1967.[2][3] More recently developed reactions for its synthesis include pyrolysis of ethylenetetracarboxylic acid[4]

Ethylenetetracarboxylic dianhydride via acid dehydration
Ethylenetetracarboxylic dianhydride via acid dehydration

and microwave pyrolysis of solid Meldrum's acid.[1] In this latter route, two molecules of the Meldrum's acid are believed to undergo a reductive dimerization to give an alkene linkage with one "Meldrum's acid" ring on each end. The rings then open via hydrolysis of the esters to form ethylenetetracarboxylic acid, and then the carboxylic acid units recyclize with different partners (cis on each side of the alkene) as in the simple pyrolysis of the tetra-acid.

Ethylenetetracarboxylic acid via Meldrum's acid
Ethylenetetracarboxylic acid via Meldrum's acid
Ethylenetetracarboxylic dianhydride
Skeletal formula
Space-filling model
IUPAC name
3D model (JSmol)
Molar mass 168.060 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

See also


  1. ^ a b Avat (Arman) Taherpour (2010), Microwave-assisted solid phase conversion study of Meldrum’s acid to ethylenetetracarboxylic dianhydride (C6O6) Spectrochimica Acta Part A, volume 75, pages 493–497. doi:10.1016/j.saa.2009.10.049
  2. ^ Jürgen Sauer, Barbara Schröder, Richard Wiemer (1967), Eine Studie der Diels-Alder-Reaktion, VI. Kinetischer Nachweis des Moleküls C6O6 (Dianhydrid der Äthylentetracarbonsäure). Chemische Berichte Volume 100 Issue 1, Pages 306-314 doi:10.1002/cber.19671000135
  3. ^ Jürgen Sauer, Barbara Schröder, Albrecht Mielert (1967), Eine Studie der Diels-Alder-Reaktion, VII. Reaktionen des Dianhydrids der Äthylentetracarbonsäure (C6O6). Chemische Berichte Volume 100 Issue 1, Pages 315-322 doi:10.1002/cber.19671000136
  4. ^ John M. Patterson, Nabeel F. Haidar, Loren L. Braun and Walter T. Smith, Jr. (1981), The pyrolytic behavior of ethylenetetracarboxylic acid. Journal of Analytical and Applied Pyrolysis, Volume 2, Issue 4, Pages 331-337 doi:10.1016/0165-2370(81)80005-8
Benzoquinonetetracarboxylic dianhydride

Benzoquinonetetracarboxylic dianhydride is an organic compound with formula C10O8 (an oxide of carbon) which can be seen as the result of removing two molecules of water H2O from benzoquinonetetracarboxylic acid.

It is a red solid, stable in dry air up to 140 °C and insoluble in ether, carbon tetrachloride, dichloromethane, and carbon disulfide. It reacts with acetone, ethyl acetate, tetrahydrofuran, ethanol, and water. It dissolves in methylated derivatives of benzene to give solutions ranging from orange to violet. When the molecule is exposed to moist air it quickly turns blue.

The compound was synthesized in 1963 by P. R. Hammond who claimed it was "one of

the strongest π-electron acceptors so far described."


The molecular formula C6O6 (molar mass : 168.06 g/mol) may refer to:


Ethylenetetracarboxylic dianhydride


Cyclohexanehexone, also known as hexaketocyclohexane and triquinoyl, is an organic compound with formula C6O6, the sixfold ketone of cyclohexane. It is an oxide of carbon (an oxocarbon), a hexamer of carbon monoxide.

The compound is expected to be highly unstable, unlike the cyclohexanehexathione analog, and as of 1999 had only been observed as an ionized fragment during mass spectrometry studies.

Ethylenetetracarboxylic acid

Ethylenetetracarboxylic acid is an organic compound with formula C6H4O8, or (HO(OC)-)2C=C(-(CO)OH)2.

By removal of four protons, the acid yields the anion C6O4−8, ethylenetetracarboxylate, which is one of the oxocarbon anions (consisting solely of oxygen and carbon. By loss of 1 through 3 protons it forms the anions C6H3O−8, C6H2O2−8, and C6HO3−8, called respectively trihydrogen-, dihydrogen-, and hydrogenethylenetetracarboxylate. The same names are used for the corresponding esters.

The acid can be obtained by hydrolysis of tetraethyl ethylenetetracarboxylate, which in turn can be obtained from diethyl dibromomalonate with sodium iodide.Ethylenetetracarboxylic dianhydride, a twofold acid anhydride of this compound, can be formed by direct dehydration at high temperature.

Organic acid anhydride

An organic acid anhydride is an acid anhydride that is an organic compound. An acid anhydride is a compound that has two acyl groups bonded to the same oxygen atom. A common type of organic acid anhydride is a carboxylic anhydride, where the parent acid is a carboxylic acid, the formula of the anhydride being (RC(O))2O. Symmetrical acid anhydrides of this type are named by replacing the word acid in the name of the parent carboxylic acid by the word anhydride. Thus, (CH3CO)2O is called acetic anhydride. Mixed (or unsymmetrical) acid anhydrides, such as acetic formic anhydride (see below), are known, whereby reaction occurs between two different carboxylic acids. Nomenclature of unsymmetrical acid anhydrides list the names of both of the reacted carboxylic acids before the word "anhydride" (for example, the dehydration reaction between benzoic acid and propanoic acid would yield "benzoic propanoic anhydride").One or both acyl groups of an acid anhydride may also be derived from another type of organic acid, such as sulfonic acid or a phosphonic acid. One of the acyl groups of an acid anhydride can be derived from an inorganic acid such as phosphoric acid. The mixed anhydride 1,3-bisphosphoglyceric acid, an intermediate in the formation of ATP via glycolysis, is the mixed anhydride of 3-phosphoglyceric acid and phosphoric acid. Acidic oxides are also classified as acid anhydrides.


An oxocarbon or oxide of carbon is a chemical compound consisting only of carbon and oxygen.The simplest and most common oxocarbons are carbon monoxide (CO) and carbon dioxide (CO2) with IUPAC names carbon(II) oxide and carbon(IV) oxide respectively. Many other stable (practically if not thermodynamically) or metastable oxides of carbon are known, but they are rarely encountered, such as carbon suboxide (C3O2 or O=C=C=C=O) and mellitic anhydride (C12O9).

While textbooks will often list only the first three, and rarely the fourth, a large number of other oxides are known today, most of them synthesized since the 1960s. Some of these new oxides are stable at room temperature. Some are metastable or stable only at very low temperatures, but decompose to simpler oxocarbons when warmed. Many are inherently unstable and can be observed only momentarily as intermediates in chemical reactions or are so reactive that they can exist only in the gas phase or under matrix isolation conditions.

The inventory of oxocarbons appears to be steadily growing. The existence of graphene oxide and of other stable polymeric carbon oxides with unbounded molecular structures suggests that many more remain to be discovered.

Common oxides
Exotic oxides
Compounds derived from oxides


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