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Synthesis of Allylbenzene and Phenyl-2-bromopropane


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Allylbenzene [1]

Phenylmagnesium bromide was prepared from 67.8g Mg and 440g og bromobenzene and this was poured into a 3L 3-neck flask, care being taken that no unchanged magnesium was present. 295g of allyl bromide were aded at such a rate as to cause gente reflux. After addition was complete, the mixture was stirred and refluxed for two hours, and was then poured into iced dilute sulfuric acid. The ether layer was separated, washed with water, and dried over anhydrous sodium sulfate. The ether was distilled off, and the residue fractionated under reduced pressure. The main fraction of allylbenzene distilled at 65-70/20 mmHg, giving 230g (78%).

Phenyl-2-Bromopropane [1]

200g GAA containing 150g HBr were placed in a 500ml bottle in an ice bath, and 100g of allylbenzene was added. The bottle was stoppered, and it was allowed to come to room temp slowly with occasional shaking. In 10-12h, the original two layers merged into a clear red solution. After 24h, the solution was poured on crushed ice. The crude bromide was separated, and the aqueous layer extracted with petroleum ether. The two fractions were combined, washed with water and Na2CO3(aq) and dried over Na2SO4. The solvent was evaporated, and the residue vacuum distilled at 90-91C/3mmHg to give 235g (92% yield).


References

[1] H E Carter, J Biol Chem 108, 619 (1935)