Mellitic anhydride

Mellitic anhydride, the anhydride of mellitic acid, is an organic compound with the formula C12O9.

Containing no other elements (e.g., hydrogen) besides carbon and oxygen, mellitic anhydride is an oxide of carbon (oxocarbon), and, along with CO2, CO, and C3O2, is one of the only four that are reasonably stable under standard conditions. It is a white sublimable solid, apparently obtained by Justus Liebig and Friedrich Wöhler in 1830 in their study of mellite ("honey stone") and has the empirical formula C4O3.[2][3][4] The substance was properly characterized in 1913 by H. Meyer and K. Steiner.[5][6] It retains the aromatic character of the benzene ring.[7][8]

Mellitic anhydride
Mellitic trianhydride
Mellitic anhydride molecule
IUPAC name
Preferred IUPAC name
3D model (JSmol)
Molar mass 288.123 g·mol−1
Appearance colorless solid[1]
Melting point 161 °C; 322 °F; 434 K [1]
Vapor pressure 0.000004 mmHg (20°C)[1]
US health exposure limits (NIOSH):
PEL (Permissible)
REL (Recommended)
TWA 0.005 ppm (0.04 mg/m3) Should be handled in the workplace as an extremely toxic substance.[1]
IDLH (Immediate danger)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).


  1. ^ a b c d e f NIOSH Pocket Guide to Chemical Hazards. "#0635". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ Wöhler, F. (1826). "Ueber die Honigsteinsäure". Annalen der Physik und Chemie. 83 (7): 325–334. doi:10.1002/andp.18260830706.
  3. ^ Liebig, J.; Wöhler, F. (1830). "Ueber die Zusammensetzung der Honigsteinsäure". Annalen der Physik und Chemie. 94 (2): 161–164. doi:10.1002/andp.18300940202.
  4. ^ Erdmann, O. L.; Marchand, R. F. (1848). "Ueber die Mellithsäure". Journal für Praktische Chemie. 43 (2/3): 129–144. doi:10.1002/prac.18480430113.
  5. ^ Meyer, H.; Steiner, K. (1913). "Über ein neues Kohlenoxyd C12O9" [A new carbon oxide C12O9]. Berichte der Deutschen Chemischen Gesellschaft. 46 (1): 813–815. doi:10.1002/cber.191304601105.
  6. ^ Bugge, G. (1914). "Chemie: Ein neues Kohlenoxyd". Naturwissenschaftliche Wochenschrift. 13/29 (12): 188.
  7. ^ Fowler, P. W.; Lillington, M. (2007). "Mellitic Trianhydride, C12O9: The Aromatic Oxide of Carbon". Journal of Chemical Information and Modeling. 47 (3): 905–908. doi:10.1021/ci600547n.
  8. ^ Ermer, O.; Neudörfl, J. (2000). "Structure of Mellitic Trianhydride". Helvetica Chimica Acta. 83 (1): 300–309. doi:10.1002/(SICI)1522-2675(20000119)83:1<300::AID-HLCA300>3.0.CO;2-L.

1,2,4-Trimethylbenzene, also known as pseudocumene, is an organic compound with the chemical formula C6H3(CH3)3. Classified as an aromatic hydrocarbon, it is a flammable colorless liquid with a strong odor. It is nearly insoluble in water but soluble in organic solvents. It occurs naturally in coal tar and petroleum (about 3%).


Benzotriyne or cyclo[6]carbon is a hypothetical chemical compound, an allotrope of carbon with molecular formula C6. The molecule is a ring of six carbon atoms, connected by alternating triple and single bonds. It is, therefore, a potential member of the cyclo[n]carbon family.

There have been a few attempts to synthesize benzotriyne, e.g. by pyrolysis of mellitic anhydride, but without success as of 2011.

Recent investigations have concluded that benzotriyne is unlikely to exist due to the large angle strain. A likely alternative isomer would be a cyclic cumulene called cyclohexahexaene, which should itself be a metastable species.


Carbon (from Latin: carbo "coal") is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Three isotopes occur naturally, 12C and 13C being stable, while 14C is a radionuclide, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity.Carbon is the 15th most abundant element in the Earth's crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. Carbon's abundance, its unique diversity of organic compounds, and its unusual ability to form polymers at the temperatures commonly encountered on Earth enables this element to serve as a common element of all known life. It is the second most abundant element in the human body by mass (about 18.5%) after oxygen.The atoms of carbon can bond together in different ways, termed allotropes of carbon. The best known are graphite, diamond, and amorphous carbon. The physical properties of carbon vary widely with the allotropic form. For example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper (hence its name, from the Greek verb "γράφειν" which means "to write"), while diamond is the hardest naturally occurring material known. Graphite is a good electrical conductor while diamond has a low electrical conductivity. Under normal conditions, diamond, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials. All carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form at standard temperature and pressure. They are chemically resistant and require high temperature to react even with oxygen.

The most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and transition metal carbonyl complexes. The largest sources of inorganic carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil, and methane clathrates. Carbon forms a vast number of compounds, more than any other element, with almost ten million compounds described to date, and yet that number is but a fraction of the number of theoretically possible compounds under standard conditions. For this reason, carbon has often been referred to as the "king of the elements".

Compounds of carbon

Compounds of carbon are defined as chemical substances containing carbon. More compounds of carbon exist than any other chemical element except for hydrogen. Organic carbon compounds are far more numerous than inorganic carbon compounds. In general bonds of carbon with other elements are covalent bonds. Carbon is tetravalent but carbon free radicals and carbenes occur as short-lived intermediates. Ions of carbon are carbocations and carbanions are also short-lived. An important carbon property is catenation as the ability to form long carbon chains and rings.


Mellite, also called honeystone, is an unusual mineral being also an organic chemical. Chemically identified as an aluminium salt of mellitic acid; that is, aluminium benzene hexacarboxylate hydrate, with the chemical formula Al2C6(COO)6·16H2O.It is a translucent honey-coloured crystal which can be polished and faceted to form striking gemstones. It crystallizes in the tetragonal system and occurs both in good crystals and as formless masses. It is soft with a Mohs hardness of 2 to 2.5 and has a low specific gravity of 1.6.It was discovered originally in 1789 at Artern in Thuringia, Germany. It has subsequently also been found in Russia, Austria, the Czech Republic, and Hungary. It was named from the Greek μέλι meli "honey", in allusion to its color.It is found associated with lignite and is assumed to be formed from plant material with aluminium derived from clay.

Mellitic acid

Mellitic acid, also called graphitic acid or benzenehexacarboxylic acid, is an acid first discovered in 1799 by Martin Heinrich Klaproth in the mineral mellite (honeystone), which is the aluminium salt of the acid. It crystallizes in fine silky needles and is soluble in water and alcohol.

Organic compound

In chemistry, organic compounds are generally any chemical compounds that contain carbon. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The study of the properties, reactions, and syntheses of organic compounds comprises the discipline known as organic chemistry. For historical reasons, a few classes of carbon-containing compounds (e.g., carbonates and cyanide salts), along with a handful of other exceptions (e.g., carbon dioxide), are not classified as organic compounds and are considered inorganic. Other than those just named, little consensus exists among chemists on precisely which carbon-containing compounds are excluded, making any rigorous definition of an organic compound elusive.Although organic compounds make up only a small percentage of the Earth's crust, they are of central importance because all known life is based on organic compounds. Living things incorporate inorganic carbon compounds into organic compounds through a network of processes (the carbon cycle) that begins with the conversion of carbon dioxide and a hydrogen source like water into simple sugars and other organic molecules by autotrophic organisms using light (photosynthesis) or other sources of energy. Most synthetically produced organic compounds are ultimately derived from petrochemicals consisting mainly of hydrocarbons, which are themselves formed from the high pressure and temperature degradation of organic matter underground over geological timescales. This ultimate derivation notwithstanding, organic compounds are no longer defined as compounds originating in living things, as they were historically.

In chemical nomenclature, an organyl group, frequently represented by the letter R, refers to any monovalent substituent whose open valence is on a carbon atom.


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.

Oxocarbon anion

In chemistry, an oxocarbon anion is a negative ion consisting solely of carbon and oxygen atoms, and therefore having the general formula CxOn−y for some integers x, y, and n.

The most common oxocarbon anions are carbonate, CO2−3, and oxalate, C2O2−4. There is however a large number of stable anions in this class, including several ones that have research or industrial use. There are also many unstable anions, like CO−2 and CO−4, that have a fleeting existence during some chemical reactions; and many hypothetical species, like CO4−4, that have been the subject of theoretical studies but have yet to be observed.

Stable oxocarbon anions form salts with a large variety of cations. Unstable anions may persist in very rarefied gaseous state, such as in interstellar clouds. Most oxocarbon anions have corresponding moieties in organic chemistry, whose compounds are usually esters. Thus, for example, the oxalate moiety [–O–(C=O)2–O–] occurs in the ester dimethyl oxalate H3C–O–(C=O)2–O–CH3.

Trimellitic anhydride chloride

Trimellitic anhydride chloride is a chemical compound used to produce polyamide-imide plastic.

Common oxides
Exotic oxides
Compounds derived from oxides
Mixed oxidation states
+1 oxidation state
+2 oxidation state
+3 oxidation state
+4 oxidation state
+5 oxidation state
+6 oxidation state
+7 oxidation state
+8 oxidation state


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