Dimethylbutadiene

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Dimethylbutadiene
2,3-dimethyl-1,3-butadiene.png
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 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 208-172-0
PubChem CID
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 [1]
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:
GHS-pictogram-flamme.svg
Flash point −1 °C (30 °F; 272 K) [2]
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.

Contents

Synthesis

Dimethylbutadiene is readily prepared by an acid catalyzed dehydration reaction of pinacol: [3]

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. [4]

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. [5] The polymer had a number of deficiencies relative to natural rubber. [6] The Bayer synthesis of dimethylbutadiene involved the dehydration of pinacol, as described above. [4]

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

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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); Collective Volume, 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.