2,3-dimethyl-1,3-butadiene
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IUPAC name
2,3-Dimethyl-1,3-butadiene
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| Other names
Biisopropenyl; Diisopropenyl; 2,3-Dimethylbuta-1,3-diene; 2,3-Dimethylbutadiene; 2,3-Dimethylenebutane
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| Identifiers | |
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3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.007.430 |
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PubChem CID
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| Properties | |
| C6H10 | |
| Molar mass | 82.15 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 | |
| Main hazards | Flammable and irritant |
| GHS pictograms |  |
| Flash point | −1 °C (30 °F; 272 K) |
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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 | |
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.
Dimethylbutadiene is readily prepared by an acid catalyzed dehydration reaction of pinacol:
The current industrial route involves dimerization of propene followed by dehydrogenation.
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.
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.
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