Mellitic acid

Mellitic acid[1]
IUPAC name

Benzene-1,2,3,4,5,6-hexacarboxylic acid
Other names

Graphitic acid
Benzenehexacarboxylic acid
Identifiers
CAS number 517-60-2 Y
PubChem 2334
ChemSpider 2244 Y
DrugBank DB01681
ChEBI CHEBI:41089 Y
Jmol-3D images Image 1
Properties
Molecular formula C12H6O12
Molar mass 342.16 g/mol
Density 1.68 g/cm3, 2.078 (calc.)[2]
Melting point

>300 °C
Boiling point

678 °C (calc.)[2]
Acidity (pKa) 1.40, 2.19, 3.31, 4.78, 5.89, 6.96[3]
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Mellitic acid, also called graphitic acid or benzenehexacarboxylic acid, is an acid first discovered in 1799 by M. H. Klaproth in the mineral mellite (honeystone), which is the aluminium salt of the acid.

Contents

Preparation

Mellitic acid may be prepared by warming mellite with ammonium carbonate, boiling off the excess of the ammonium salt and adding ammonia to the solution. The precipitated alumina is filtered off, the filtrate evaporated and the ammonium salt of the acid purified by recrystallization. The ammonium salt is then converted into the lead salt by precipitation with lead acetate and the lead salt decomposed by hydrogen sulfide. The acid may also be prepared by the oxidation of pure carbon, or of hexamethyl benzene, in the cold, by alkaline potassium permanganate, or by hot concentrated nitric acid.[4]

Reactions

It crystallizes in fine silky needles and is soluble in water and alcohol. It is a very stable compound, chlorine, concentrated nitric acid and hydriodic acid having no action upon it. It is decomposed, on dry distillation, into carbon dioxide and pyromellitic acid, C10H6O8; when distilled with lime it gives carbon dioxide and benzene. Long digestion of the acid with excess of phosphorus pentachloride results in the formation of the acid chloride, which crystallizes in needles, melting at 190 °C. By heating the ammonium salt of the acid to 150–160 °C so long as ammonia is evolved, a mixture of paramide (mellimide), C6(CONHCO)3, and ammonium euchroate is obtained. The mixture may be separated by dissolving out the ammonium euchroate with water. Paramide is a white amorphous powder, insoluble in water and alcohol.

The high stability of mellitic acid salts and that they are the endproduct of the oxidation of polycyclic aromatic hydrocarbons, which are present in the solar system, made them a possible organic substance in Martian soil.[5]

Mellitates (and salts of other benzene polycarboxylic acids) of iron and cobalt have interesting magnetic properties.[6]

Mellitic anhydride

Main article: Mellitic anhydride

References

  1. ^ MSDS for mellitic acid
  2. ^ a b Curate Data: Predicted Properties: 2244. ChemSpider.com.
  3. ^ Brown, H.C., et al., in Baude, E.A. and Nachod, F.C., Determination of Organic Structures by Physical Methods, Academic Press, New York, 1955.
  4. ^ WebElements.com
  5. ^ S. A. Benner, K. G. Devine, L. N. Matveeva, D. H. Powell (2000). "The missing organic molecules on Mars". Proceedings of the National Academy of Sciences 97 (6): 2425–2430. doi:10.1073/pnas.040539497. PMC 15945. PMID 10706606. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=15945. 
  6. ^ Kurmoo M, Estournes C, Oka Y, Kumagai H, Inoue K (2005) Inorganic Chemistry volume 44, page 217

Further reading

Henry Enfield Roscoe, Carl Scholemmer, "Mellitene Group", "A Treatise on Chemistry: V.III: The Chemistry of the Hydrocarbons and their Derivatives on Organic Chemistry: P.V:529. D. Appleton and Co. (1889).

 This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press.