Durene

Durene
Skeletal formula of durene
Ball-and-stick model of the durene molecule
Names
IUPAC name
1,2,4,5-tetramethylbenzene
Identifiers
95-93-2 Yes
ChEBI CHEBI:38978 Yes
ChemSpider 6999 Yes
Jmol-3D images Image
KEGG C14534 Yes
PubChem 7269
UNII 181426CFYB Yes
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
Hazards
Main hazards Flammable
Flash point 73.9 °C (165.0 °F; 347.0 K)
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

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, m.p. −6.2 °C) and isodurene (1,2,3,5-tetramethylbenzene, m.p. −23.7 °C). Durene has an unusually high melting point, reflecting its high molecular symmetry.[1]

Production

It is a component of coal tar. It is produced by methylation of other methylated benzene compounds such as p-xylene and pseudocumene.[2][3]

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.[1] 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

Durene is an electron-rich arene, exhibiting nucleophilicity comparable to that of phenol.[1] 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.[6]

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.[7]

Safety

Durene is relatively toxic for an aromatic hydrocarbons, which tend to have low acute toxicities. The LD50 for intravenous exposure in mice is 180 mg/kg.[1]

References

  1. ↑ 1.0 1.1 1.2 1.3 Karl Griesbaum, Arno Behr, Dieter Biedenkapp, Heinz-Werner Voges, Dorothea Garbe, Christian Paetz, Gerd Collin, Dieter Mayer, Hartmut Höke “Hydrocarbons” in Ullmann's Encyclopedia of Industrial Chemistry, 2002 Wiley-VCH, Weinheim. doi:10.1002/14356007.a13_227
  2. ↑ Lee Irvin Smith (1943). "Durene". Org. Synth.; Coll. Vol. 2, p. 248
  3. ↑ Durene was first prepared in 1870 from pseudocumene. See: Paul Jannasch and Rudolph Fittig (1870) "Ueber das Tetramethylbenzol" (On tetramethylbenzene), Zeitschrift für Chemie, 6 : 161-162.
  4. ↑ E. Ador and A. Rilliet "Ueber durch Einwirkung von Chlormethyl auf Benzol in Gegenwart von Aluminiumchlorid erhaltene Kohlenwasserstoffe" Chem. Ber. 1879, volume 12, pages 329–332. doi:10.1002/cber.18790120191
  5. ↑ Packer, John; Kooy, P.; Kirk, Dr. C.M.; Wrinkles, Claire. "The Production of Methanol and Gasoline" (PDF). New Zealand Institute of Chemistry.
  6. ↑ F. Röhrscheid "Carboxylic Acids, Aromatic" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2012. doi:10.1002/14356007.a05_249
  7. ↑ 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.