In a
500-ml. three-necked flask, fitted with a
mechanical stirrer,
thermometer,
separatory funnel, and
calcium chloride tube, are placed
96 g. (56.5 ml., 0.36 mole) of redistilled phosphorus tribromide (b.p.
174–175°/740 mm.) and
50 ml. of dry benzene. From the separatory funnel,
15 g. of dry pyridine is added with stirring over a period of 15 minutes. The flask is then surrounded by an ice-salt mixture, and the contents are cooled to −5°. A mixture of
102 g. (1 mole) of redistilled tetrahydrofurfuryl alcohol (b.p.
79–80°/20 mm.) and
5 g. of dry pyridine (total pyridine, 20 g., 0.25 mole) is added slowly from the
dropping funnel with stirring over a period of 4 hours. During this time the internal temperature is kept at −5° to −3°. Stirring is continued for 1 hour longer, and the cooling bath is then allowed to warm up to room temperature.
The mixture is allowed to stand for 24–48 hours (Note
1) and is then transferred to a
500-ml. Claisen flask. Two small portions of
benzene are used for rinsing the flask. The
benzene is distilled by reducing the pressure gradually to about 60 mm. and heating the flask gently in an
oil bath (not above 90°). After the
benzene has been removed, the pressure is reduced to 5–10 mm. and the bath is heated slowly to 150–155° until no more material distils (Note
2). The crude distillate (
110–126 g.) is redistilled through an
efficient column, and the purified
tetrahydrofurfuryl bromide is collected at
69–70°/22 mm. (
61–62°/13 mm.,
49–50°/4 mm.) (Note
3). The yield is
90–102 g. (
53–61%).