Submitted by J. B. Conant and O. R. Quayle.
Checked by O. Kamm and A. O. Matthews.
1. Procedure
Five hundred grams (402 cc., 4.9 moles) of 90 per cent glycerol and
10 g. of glacial acetic acid are mixed in a weighed
1-l. flask, which is placed in an
oil bath heated to 105–110° (Note
1). A rapid stream of dry
hydrogen chloride (Note
2) is introduced into the mixture. The flask is removed from the bath from time to time and reweighed. At the end of about four hours the flask will have gained
190 g. in weight. The reaction is then complete.
The product is distilled under reduced pressure. Below
114°/14 mm.,
220–250 g. distil; this portion is mostly water. The monochlorohydrin is collected between
114° and
120°/14 mm. (Note
3), and weighs
360 g. (
66 per cent of the theoretical amount) (Note
4). About
20 g. more may be obtained by neutralizing the first fraction and separating the aqueous layer.
2. Notes
1. The same apparatus is employed as in the preparation of
glycerol α,γ-dichlorohydrin (p. 292).
3. The portion boiling
120–130°/14 mm. amounts to only
15–30 g., showing that very little of the β-compound is formed. This is further shown by the fact that the dichlorohydrin formed by continued action of
hydrogen chloride under the same conditions contains very little, if any, α,β-dichlorohydrin.
4. A light straw-colored final product is obtained in some cases.
An alternative procedure which is slower and gives slightly lower yields, but which does not require a hydrogen chloride generator, is as follows:
Three hundred grams of 90 per cent glycerol,
600 cc. of hydrochloric acid (sp. gr. 1.19), and
15 g. of glacial acetic are heated under a
reflux condenser for ten hours, in a
2-l. flask. The boiling should be very gentle in the early stage of the reaction, as considerable
hydrogen chloride vapor is evolved. As the reaction progresses, and the evolution of acid vapors diminishes, the mixture is more strongly heated.
The reaction products are distilled under ordinary pressure until the temperature of the liquid has reached 140° (
thermometer bulb immersed in the liquid). The residual products are distilled under diminished pressure, and the following fractions obtained: (1) up to 115°/11 mm.; (2)
115–117°/11 mm.; and (3)
117–170°/11 mm. (1) is mostly aqueous
hydrochloric acid; (2) is the monochlorohydrin; and (3) is
glycerol. The second fraction is redistilled, and the portion boiling at
115–118°/11 mm. or
133–136°/20 mm. is collected. The yield is
190–205 g.,
59–63 per cent of the theoretical amount. Higher yields are possible by reworking the residues in a procedure which is in essential accordance with that outlined.
1
3. Discussion
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