Org. Synth. 1922, 2, 33
DOI: 10.15227/orgsyn.002.0033
GLYCEROL α-MONOCHLOROHYDRIN
[1,2-Propanediol, 3-chloro-]
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).
2.
Two kilograms of concentrated sulfuric acid and
750 g. of concentrated hydrochloric acid are sufficient to produce the necessary amount of
hydrogen chloride. See
pp. 293 and
534 for the generation of
hydrogen chloride.
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
Glycerol α-monochlorohydrin can be prepared by the action of
hydrogen chloride on
glycerol2 or on
glycerol mixed with an equal volume of
acetic acid3 or other organic acid
4 as catalyst, or on
glycerol with the
ester of an organic or inorganic acid as a catalyst;
5 by the action of aqueous
hydrochloric acid on
glycerol6 alone or with an
organic acid (1–2 per cent), such as acetic, as a catalyst;
7 and by heating
epichlorohydrin with water in the presence of
sulfuric acid as a catalyst.
8
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
ester
Glycerol α,γ-dichlorohydrin
acetic
Glycerol α-monochlorohydrin
sulfuric acid (7664-93-9)
hydrogen chloride,
hydrochloric acid (7647-01-0)
acetic acid (64-19-7)
glycerol (56-81-5)
Epichlorohydrin (106-89-8)
1,2-Propanediol, 3-chloro- (96-24-2)
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