Durene

Durene, or 1,2,4,5-tetramethylbenzene, is an organic compound with the formula C6H2(CH3)4. It is a colourless solid with a sweet odor. The compound is classified as an alkylbenzene. It is one of three isomers of tetramethylbenzene, the other two being prehnitene (1,2,3,4-tetramethylbenzene) and isodurene (1,2,3,5-tetramethylbenzene). Durene has an unusually high melting point (79.2 °C), reflecting its high molecular symmetry.

Durene
Names
IUPAC name
1,2,4,5-tetramethylbenzene
Other names
Durol
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.002.242
KEGG
UNII
Properties
C10H14
Molar mass 134.21816
Density 0.868 g/cm3
Melting point 79.2 °C (174.6 °F; 352.3 K)
Boiling point 192 °C (378 °F; 465 K) at 760mmHg
-101.2·10−6 cm3/mol
Hazards
Main hazards Flammable
Flash point 73.9 °C (165.0 °F; 347.0 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Production

It is a component of coal tar and was first prepared from pseudocumene in 1870.[1] It is produced by methylation of other methylated benzene compounds such as p-xylene and pseudocumene.[2]

C6H4(CH3)2 + 2 CH3Cl → C6H2(CH3)4 + 2 HCl

In industry, a mixture of xylenes and trimethylbenzenes is alkylated with methanol. Durene can be separated from its isomers by selective crystallization, exploiting its high melting point.[3] The original synthesis of durene involved a similar reaction starting from toluene.[4]

Durene is a significant byproduct of the production of gasoline from methanol via the "MTG (Methanol to Gasoline) process".[5]

Reactions and uses

It is a relatively easily oxidized benzene derivative, with E1/2 of 2.03 V vs NHE.[6] Its nucleophilicity is comparable to that of phenol.[7] It is readily halogenated on the ring for example. Nitration gives the dinitro derivative, a precursor to duroquinone. In industry, it is the precursor to pyromellitic dianhydride, which is used for manufacturing curing agents, adhesives, coating materials. It is used in the manufacture of some raw materials for engineering plastics (polyimides) and cross-linking agent for alkyd resins.[8] It is also a suitable starting material for the synthesis of hexamethylbenzene.[2]

With a simple proton NMR spectrum comprising two signals due to the 2 aromatic hydrogens (2H) and four methyl groups (12H), durene is used as an internal standard.[9]

Safety

Durene is not a skin irritant nor a skin sensitizer or eye irritant. Durene is only slightly toxic on an acute toxicologic basis and only poses an acute health hazard when ingested in excessive quantities [10]

References
  1. Jannasch, Paul; Fittig, Rudolph (1870). "Ueber das Tetramethylbenzol" [On tetramethylbenzene]. Zeitschrift für Chemie. 6: 161–162.
  2. Smith, Lee Irvin (1930). "Durene". Organic Syntheses. 10: 32. doi:10.15227/orgsyn.010.0032.; Collective Volume, 2, p. 248
  3. Griesbaum, Karl; Behr, Arno; Biedenkapp, Dieter; Voges, Heinz-Werner; Garbe, Dorothea; Paetz, Christian; Collin, Gerd; Mayer, Dieter; Höke (2002). "Hydrocarbons". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a13_227.
  4. Ador, E.; Rilliet, A. (1879). "Ueber durch Einwirkung von Chlormethyl auf Benzol in Gegenwart von Aluminiumchlorid erhaltene Kohlenwasserstoffe" [Hydrocarbons obtained by the action of methyl chloride on benzene in the presence of aluminum chloride]. Chem. Ber. 12: 329–332. doi:10.1002/cber.18790120191.
  5. Packer, John; Kooy, P.; Kirk, C. M.; Wrinkles, Claire. "The Production of Methanol and Gasoline" (PDF). New Zealand Institute of Chemistry. Archived (PDF) from the original on September 28, 2006.
  6. Howell, J. O.; Goncalves, J. M.; Amatore, C.; Klasinc, L.; Wightman, R. M.; Kochi, J. K. (1984). "Electron transfer from aromatic hydrocarbons and their pi-complexes with metals. Comparison of the standard oxidation potentials and vertical ionization potentials". Journal of the American Chemical Society. 106 (14): 3968–3976. doi:10.1021/ja00326a014.
  7. Griesbaum, Karl; Behr, Arno; Biedenkapp, Dieter; Voges, Heinz-Werner; Garbe, Dorothea; Paetz, Christian; Collin, Gerd; Mayer, Dieter; Höke, Hartmut (2002). "Hydrocarbons". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a13_227. ISBN 3527306730.
  8. Röhrscheid, F. (2012). "Carboxylic Acids, Aromatic". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a05_249. ISBN 978-3527306732.
  9. e.g. in Petr K. Sazonov, Vasyli A. Ivushkin, Galina A. Artamkina, and Irina P. Beletskaya (2003). "Metal carbonyl anions as model metal-centered nucleophiles in aromatic and vinylic substitution reactions". Arkivoc. 10: 323–334.CS1 maint: multiple names: authors list (link)
  10. Dennis W. Lynch, Vernon B. Perone, Ronald L. Schuler, William B. Ushry & Trent R. Lewis, Journal Drug and Chemical Toxicology Volume 1, 1978 - Issue 3, Pages 219-230 (2008)
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