Combine 25 g of styrene with 35 mL of DCM, put it in a freezer to cool down to 0°C. Then combine 17.4 mL of bromine with 35 mL of DCM, pour it into an addition funnel and rapidly add some of it to the styrene mixture over with stirring, when the solution becomes lukewarm put the mixture in a cold water bath and add slowly the bromine mixture. Then distill the DCM off, until the mixture becomes white. Recrystallize in 600 g of 67% aqueous isopropanol.
Bromination of styrene
The crude product
Filtering the recrystallized product
The pure product