[37 p535]—A flask is placed in an ice bath and in it is stirred 50g benzene and 0.5ml_ pyridine (slightly watched chemical). A condenser is attached and a drying tube made from a vacuum adaptor is prepared so that it has a hose extending to a glass of water (this will allow for the collection of HBr gas that will form during the reaction). The drying tube with its hose is not yet attached to the condenser. 125g (40ml_) of liquid bromine is poured down into the reaction flask through the condenser and the drying tube is immediately attached. A vigorous reaction will occur and when it has died down the reaction is allowed to warm up to 25-30°C by removal of the ice bath and stir there for 1 hour. After 1 hour the solution is brought up to 65-70°C and kept there for 45 minutes or until no more red bromine vapors can be seen. Remember, all of that HBr vapor that bubbled into the glass of water can be salvaged as perfectly usable 48% HBr solution by distilling that water and collecting what comes over at 126°C.
The reaction solution is washed once with water, three times with 5% NaOH and once more with water. The benzene layer is dried through Na2S04 and distilled with no vacuum collecting the fraction between 150-170°C. This fraction is then redistilled and the fraction coming over at 154-157°C is the pure bromobenzene.
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