A dry 1-l. round-bottomed flask with five outlets is equipped with a sealed stirrer, a 500-ml. dropping funnel, a reflux condenser attached to a calcium chloride tube, an inlet for dry nitrogen (a weak stream of which is maintained through all the reaction until the hydrolysis step), and a thermometer reaching close to the bottom. In the flask are placed 9.0 g. (0.38 g. atom) of magnesium turnings, a crystal of iodine, and about 25 ml. of dry ether. With stirring, about 15 ml. of a solution of 88.5 g. (0.38 mole) of p-dibromobenzene (Note 1) in 500 ml. of dry ether (Note 2) is added at once. When the reaction has started, the remaining ether solution is added at a rate which maintains rapid refluxing. After the p-dibromobenzene has been added, the mixture is stirred at room temperature for 1.5 hours.

The mixture is then cooled by means of an ice-sodium chloride bath. When the internal temperatures has reached −7°, a solution of 71.8 g. (0.33 mole) of chlorodiphenylphosphine (Note 3) in 100 ml. of dry ether is added at such a rate that the internal temperature does not exceed +10°. The addition requires about 1.25 hours. The cooling bath is then removed and stirring continued for 1.5 hours. The flask is then again immersed in an icesodium chloride bath, and 150 ml. of a cold saturated aqueous ammonium chloride solution is added slowly. The ether is decanted and the remainder acidified with hydrochloric acid and extracted three times with 125 ml. of benzene each (Note 4). From the combined ether and benzene solutions, the solvents are evaporated and the residue is distilled at reduced pressure. After the low-boiling material, some p-dibromobenzene distills and crystallizes in the distillation bridge. At 2 × 10⁻² mm., heating is continued until the phosphine reaches the stillhead. At this stage the distillation is interrupted, the stillhead and condenser containing p-dibromobenzene replaced by a clean, short distillation bridge without condenser, and the phosphine distilled at 2 × 10⁻² to 10⁻³ mm., no forerun being taken (Note 5). The main bulk distills at 180–185° (2 × 10⁻² mm.). The colorless, oily distillate begins to crystallize in the receiving flask during or shortly after the distillation (Note 6) and weighs 81–83 g. (73–77% yield) (Note 7), m.p. 64–71°. This material is sufficiently pure for further reactions, e.g., Grignard reaction. A sample may be recrystallized from methanol to give colorless needles, m.p. 79–80°.