Submitted by Donald Starr and R. M. Hixon.
Checked by John R. Johnson and H. B. Stevenson.
1. Procedure
A
500-cc. three-necked flask containing
114 g. (1.58 moles) of tetrahydrofuran (p. 566) is fitted with a
reflux condenser, a
thermometer dipping into the liquid, and a
bent glass tube arranged to introduce gaseous
hydrogen chloride (Note
1) near the bottom of the flask. The upper end of the reflux condenser is connected to a
150-cc. distilling flask cooled in an ice-salt mixture to trap material entrained by the
hydrogen chloride.
The
tetrahydrofuran is heated to the boiling point (
64–65°), and a slow stream of
hydrogen chloride is bubbled into the liquid. As the reaction proceeds the temperature of the boiling liquid increases, slowly at first and then more rapidly, until it is above 100° (after about four hours' heating). At the end of about five hours the temperature remains practically constant in the range 103.5–105.5°, and the reaction is stopped. The light brown liquid is cooled, transferred to a
250-cc. Claisen flask having a 20-cm. fractionating side arm, and fractionated at reduced pressure, using a
water aspirator. A large quantity of
hydrogen chloride is evolved at the start of the distillation and a low pressure cannot be obtained until this has been removed. Throughout the fractionation a trap cooled to −15° in an ice-salt mixture is used to collect the recovered
tetrahydrofuran.
After removal of a small amount of low-boiling material the main fraction distils in the range
80–90°/14 mm. or
65–75°/7 mm. (Note
2) and weighs
95–100 g. A small amount (5–10 g.) of high-boiling material remains. The crude product on refractionation yields
93–98 g. (
54–57 per cent of the theoretical amount) of pure
tetramethylene chlorohydrin boiling over a one-degree interval,
81–82°/14 mm. or
70–71°/7 mm. (Note
3) and (Note
4).
2. Notes
3. For recovery of
tetrahydrofuran, the condensate from the cooling traps and the low-boiling material from the fractionations are combined, cooled in an
ice bath, and treated carefully with
15–20 cc. of 40 per cent alkali. The upper layer is separated, dried with a little
calcium chloride, and distilled. The recovered
tetrahydrofuran, b.p.
64–67°, weighs
20–22 g. (
17–19 per cent of the original material). The residue (12–14 g.) remaining after distillation of the
tetrahydrofuran distils at
43–45°/10 mm. and is
tetramethylene dichloride.
3. Discussion
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