Trimethylethylene dibromide

A modification of this reaction is the hydrolysis and rearrangement of olefin dibromides. The most successful of these conversions is the preparation of methylisopropyl ketone (59%) from trimethylethylene dibromide. ... 

To the reaction flask containing the crude trimethylethylene dibromide is added 540 cc. of water, and the flask is fitted with a long reflux condenser and a mercury-sealed stirrer (Notes 3 and 4). The mixture is refluxed with stirring for three to five hours until hydrolysis is practically complete (Note 5). The reflux condenser is then replaced by a condenser for distillation, and the crude methyl fio-propyl ketone is removed from the reaction mixture by direct distillation, with stirring, until the temperature rises (Note 6) and the oil nearly stops coming over (about one and one-half hours), or until the oil coming over is heavier than water. The residue in the flask can be distilled to yield about 380 cc. of constant-boiling hydrobromic acid. 

Trimethylethylene dibromide has been obtained by adding bromine to trimethylethylene and to tertiary amyl alcohol. Methyl iso-propyl ketone has been prepared by heating trimethylethylene glycol (2-methyl-2,3-dihydroxybutane) with dilute hydrochloric acid, by heating trimethylethylene chloro-hydrin (2-methyl-2-hydroxy-3-chlorobutane) in a sealed tube with water, by boiling trimethylethylene dibromide with lead oxide (PbO) and water, by heating trimethylethylene dibromide with water, by the action of iso-propylmagnesium bromide on acetic anhydride, and by a variety of other methods not particularly related to the one here described. ... 

The crude trimethylethylene dibromide can be purified by washing with sodium carbonate solution and water, drying, and distilling under reduced pressure b.p. 49-51 °/ii mm. 60-70 per cent yield. The losses in purification, however, result in a slightly decreased over-all yield of ketone hydrolysis of the purified dibromide gave a 78 per cent yield of ketone. 

This conclusion can probably be extrapolated to trisubstituted alkenesl4 since trimethylethylene affords 19 % dibromide and the Markovnikov methoxy-bromoadduct only (ref. 3). 

Trimethylene dibromide, dl21 Trimethylene dimercaptan, pi95 Trimethylene glycol, pi92 Trimethylethylene, ml66 Trimethylgermanium bromide, b437... 

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