Dimethylbutadiene

Dimethylbutadiene
Names
Preferred IUPAC name
2,3-Dimethylbuta-1,3-diene
Other names
Biisopropenyl; Diisopropenyl; 2,3-Dimethylbutadiene; 2,3-Dimethylenebutane
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.007.430 Edit this at Wikidata
EC Number
  • 208-172-0
UNII
  • InChI=1S/C6H10/c1-5(2)6(3)4/h1,3H2,2,4H3
    Key: SDJHPPZKZZWAKF-UHFFFAOYSA-N
  • InChI=1/C6H10/c1-5(2)6(3)4/h1,3H2,2,4H3
    Key: SDJHPPZKZZWAKF-UHFFFAOYAQ
  • CC(=C)C(=C)C
Properties
C6H10
Molar mass 82.146 g·mol−1
Density 0.7222g / cm3
Melting point −76 °C (−105 °F; 197 K)
Boiling point 69 °C (156 °F; 342 K)
Vapor pressure 269 mm Hg (37.7 °C)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Flammable and irritant
GHS labelling:
GHS02: Flammable
Flash point −1 °C (30 °F; 272 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Dimethylbutadiene, formally referred to as 2,3-dimethyl-1,3-butadiene, is an organic compound with the formula (CH3)2C4H4. It is colorless liquid which served an important role in the early history of synthetic rubber. It is now a specialty reagent.

Synthesis

Dimethylbutadiene is readily prepared by an acid catalyzed dehydration reaction of pinacol:

HO(CH3)2C−C(CH3)2OH → CH3(CH2=C−C=CH2)CH3 + 2 H2O

The current industrial route involves dimerization of propene followed by dehydrogenation.

Applications

In 1909, Fritz Hofmann and a team working at Bayer succeeded in polymerizing dimethylbutadiene. It was then called methyl isoprene because it has one more methyl group than isoprene. Their polymer was the first synthetic rubber. The polymer had a number of deficiencies relative to natural rubber. The Bayer synthesis of dimethylbutadiene involved the dehydration of pinacol, as described above.

Reactions

Dimethylbutadiene readily undergoes Diels-Alder reactions and reacts faster than 1,3-butadiene. Its effectiveness in this reaction is attributed to the stabilization of the cis-conformation owing to the influence of the methyl groups on the C2 and C3 positions.

Diels-Alder reaction using 2,3-dimethyl-1,3-butadiene and N-ethylmaleimide

References

  1. ↑ Haynes, W. M.; Lide, D. R. (2012). CRC Handbook of Chemistry and Physics 93rd Ed. CRC Press/Taylor and Francis. ISBN 978-1439880494.
  2. ↑ "CSID:10124". Retrieved 19 October 2012.
  3. ↑ C. F. H. Allen, Alan Bell, L. W. Newton, and E. R. Coburn (1942). "2,3-Dimethyl-1,3-butadiene". Organic Syntheses. 22: 39{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 3, p. 312.
  4. 1 2 Griesbaum, Karl; Behr, Arno; Biedenkapp, Dieter; Voges, Heinz-Werner; Garbe, Dorothea; Paetz, Christian; Collin, Gerd; Mayer, Dieter; Höke, Hartmut (2000), "Hydrocarbons", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a13_227, ISBN 3527306730.
  5. ↑ The Moving Powers of Rubber, Leverkusen, Germany: LANXESS AG: 20.
  6. ↑ "A Poor Substitute". Retrieved 18 October 2012.