A 1-l. round-bottomed flask is provided with a mechanical stirrer, a dropping funnel, a calcium chloride exit tube, and a thermometer which reaches nearly to the bottom of the flask. In the flask are placed 181.5 g. (1.5 moles) of allyl bromide (Note 1) and 250 cc. of dry carbon tetrachloride (Note 2). In the dropping funnel is placed 255 g. (80 cc., 1.56 moles) of bromine which has been washed once with an equal volume of concentrated sulfuric acid. The mechanical agitation is started and the flask is cooled in a mixture of ice and salt. When the temperature has fallen to −5°, the bromine is allowed to drop in slowly at such a rate that the temperature remains at about − 5° and never rises above 0° (Note 3). The addition of the bromine requires about one and one-half hours. The solution is usually orange-red in color at the end of the reaction, owing to the slight excess of bromine. It is allowed to warm up to room temperature with continuous stirring (about one-half hour) and is then transferred to a large separatory funnel. The flask is washed once with a 10–15 cc. portion of carbon tetrachloride.

A 500-cc. Claisen flask is arranged for distilling the solvent and the solution is dropped in from the funnel at such a rate that the flask is never more than two-thirds full. The Claisen flask is heated in an oil bath, and the carbon tetrachloride distils when the oil bath reaches about 120°. As much as possible of the solvent is removed at atmospheric pressure by allowing the temperature of the oil bath to rise to 150°. The remainder of the carbon tetrachloride is removed under a pressure of about 20 mm. by collecting a fraction until the thermometer registers a sudden rise (temperature of the oil bath about 120°).

The residue in the distilling flask is practically pure 1,2,3-tribromopropane (Note 4) and boils at 100–103°/18 mm. On cooling in an ice-salt mixture and scratching vigorously, the tribromopropane solidifies to a mass of white needles, which melt below room temperature. The yield is 406–413 g. (96–98 per cent of the theoretical amount). If an absolutely colorless product is desired, it is advisable to collect the first few drops of distillate separately, since they may be slightly yellow. The product on long standing becomes yellow, but when the colored product is used in reactions it gives yields that indicate a high degree of purity.