Names | |
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Preferred IUPAC name
2,3-Dimethylbuta-1,3-diene | |
Other names
Biisopropenyl; Diisopropenyl; 2,3-Dimethylbutadiene; 2,3-Dimethylenebutane
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Identifiers | |
3D model (
JSmol)
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ChemSpider | |
ECHA InfoCard | 100.007.430 |
EC Number |
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PubChem
CID
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UNII | |
CompTox Dashboard (
EPA)
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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
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Flammable and irritant |
GHS labelling: | |
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).
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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: [3]
The current industrial route involves dimerization of propene followed by dehydrogenation. [4]
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]
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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link); Collected Volumes, vol. 3, p. 312.