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.[1] The polymer had a number of deficiencies relative to natural rubber.[2] The Bayer synthesis of dimethylbutadiene involved the dehydration of pinacol, as described above.[3]
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.