(A) Pentaerythrityl Bromide.—One hundred twenty-five grams (0.92 mole) of dry pentaerythritol (Org. Syn. Coll. Vol. I, 1941, 425) is placed in a 500-cc. round-bottomed flask provided with an air-cooled reflux condenser bearing at the upper end a long-stemmed dropping funnel and a bent glass tube. The tube is connected to a suitable trap for absorbing the large quantity of hydrogen bromide which is evolved. The flask is heated on a steam bath, and 500 g. (175 cc., 1.85 moles) of freshly distilled phosphorus tribromide (p. 359) is added cautiously from the dropping funnel. When this addition has been completed the steam bath is replaced by an oil bath and the temperature is raised gradually to 170–180° (Note 1). After heating at this temperature for twenty hours, the orange-red reaction mixture is transferred to a beaker containing 1 l. of cold water and stirred thoroughly to reduce the lumps to a small size. The red, flocculent material is filtered with suction and washed several times with hot water; finally it is washed thoroughly with two 200-cc. portions of cold 95 per cent ethyl alcohol (Note 2). After drying, the material is transferred to a large Soxhlet extractor and extracted exhaustively with 95 per cent alcohol (Note 3). The pentaerythrityl bromide separates from the alcohol and after cooling is collected with suction. The yield of crude product melting at 158–160° is 245–270 g. (69–76 per cent of the theoretical amount); this material is sufficiently pure for conversion to the iodide (Note 4). For purification, the crude product may be recrystallized from 95 per cent alcohol, using 30 cc. of solvent per gram; the melting point is raised to 163°, and the recovery is about 85 per cent.

(B) Pentaerythrityl Iodide.—In a 500-cc. round-bottomed flask fitted with a reflux condenser, a mixture of 100 g. (0.67 mole) of sodium iodide (dried at 120°), 300 cc. (240 g.) of ethyl methyl ketone (Note 5), and 50 g. (0.13 mole) of crude pentaerythrityl bromide (m.p. 158–160°) is refluxed on a steam bath for forty-eight hours. The condenser is set for distillation, the solvent is distilled, and the residue is washed into a hot Büchner funnel with hot water. The product is washed thoroughly on the funnel with boiling water, pressed well, and transferred to a large Soxhlet extractor. To remove impurities the material is extracted with boiling 95 per cent alcohol until a sample removed from the extraction thimble melts at 233° (Note 6). The product is then removed from the thimble and dried; the yield is 66–73 g. (89–98 per cent of the theoretical amount). The crude product may be recrystallized from hot benzene, using about 18 cc. of solvent per gram. The recovery is about 80 per cent, and the melting point is not changed.