Org. Synth. 1922, 2, 13
DOI: 10.15227/orgsyn.002.0013
α,γ-DICHLOROACETONE
[2-Propanone, 1,3-dichloro-]
Submitted by J. B. Conant and O. R. Quayle.
Checked by O. Kamm, A. D. Dox, and L. Yoder.
1. Procedure
In a
2-l. flask are placed
375 g. (1.3 moles) of commercial sodium dichromate (Note 1), 225 cc. of water, and
300 g. (2.3 moles) of glycerol α,γ-dichlorohydrin (p. 292) (b.p.
68–75°/14 mm.). The flask is set in a
water bath and equipped with a
thermometer and a
mechanical stirrer (Note 2). The contents are vigorously stirred, and
450 g. (245 cc.) of concentrated sulfuric acid, diluted with 115 g. of water, are introduced during the course of seven to eight hours. It is convenient to add the acid at ten-minute intervals. The temperature is kept between 20° and 25° during the entire reaction; this is accomplished by adding a little ice to the water bath from time to time. The stirring is continued for sixteen to seventeen hours after all the acid has been added; as there is very little heat evolved during this part of the reaction, the water bath may be allowed to come to room temperature
(Note 3).
Sufficient water (300–800 cc.) is now added to the mixture to dissolve the pasty chromium salts (Note 4). The mass of crystals is then rapidly filtered on a Büchner funnel and sucked as dry as possible. The crystals are then transferred to a small laboratory centrifuge and centrifuged for several minutes. The crystals are washed in the centrifuge with about 15–25 cc. of ice water, then with 10–15 cc. of cold petroleum ether, and finally centrifuged until as dry as possible (Note 5). The crude dichloroacetone is dried in a vacuum desiccator over sulfuric acid overnight. It weighs about 220 g.
The crude product is best purified by distillation from a 250-cc. distilling flask fitted with an air condenser. A very small fraction (10–15 g.) of low-boiling material is obtained, and the dichloroacetone (170–175°) is then collected. It solidifies in the receiver to a white crystalline mass which weighs 200–220 g. (68–75 per cent of the theoretical amount). A few grams more may be obtained by chilling the low-boiling fraction and filtering off the water.
2. Notes
1.
Commercial
sodium dichromate is hygroscopic and contains varying amounts of water. The 375 g. required in these directions is equivalent to 319 g. of anhydrous material.
2.
Great caution should be exercised in working with
dichloroacetone, as it is extremely lachrymatory and blisters the skin.
3.
The total time required for the oxidation is twenty-four hours. It is convenient to start the reaction in the morning. In this way the last part of the reaction, which requires no attention, will be accomplished during the night. The regulation of the temperature is necessary, as the reaction proceeds very slowly below 20°; on the other hand, the
dichloroacetone itself is oxidized at a somewhat higher temperature than 25°.
4.
In transferring the crystals from the reaction flask to the Büchner funnel it is necessary to use a certain amount of water to dissolve the pasty
chromium salts which are otherwise quite impossible to filter. The amount necessary varies greatly in different runs, according to the manner in which the
chromium salts separate. The amount of this water is kept low in order to dissolve as little of the product as possible. Nevertheless,
10–15 g. of
dichloroacetone are thus dissolved; this material, together with a little unchanged
dichlorohydrin, may be recovered by a long procedure involving extraction with
ether and
sodium bisulfite. This is not profitable, however.
5.
It is not necessary to wash the crystals in the centrifuge until they are white. A small amount of
chromic salt will not interfere with the subsequent purification.
3. Discussion
α,γ-Dichloroacetone can be prepared by the direct chlorination of
acetone;
1 by the oxidation of
glycerol α,γ-dichlorohydrin;
2 by the action of
hypochlorous acid on
2,3-dichloropropene;
3 and by the action of
sulfur monochloride on
epichlorohydrin.
4
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
petroleum ether
Glycerol α,γ-dichlorohydrin
chromium salts
dichlorohydrin
chromic salt
sulfuric acid (7664-93-9)
ether (60-29-7)
Epichlorohydrin (106-89-8)
sodium bisulfite (7631-90-5)
acetone (67-64-1)
sodium dichromate (7789-12-0)
hypochlorous acid (7790-92-3)
α,γ-Dichloroacetone,
2-Propanone, 1,3-dichloro- (534-07-6)
dichloroacetone (513-88-2)
2,3-dichloropropene (78-88-6)
sulfur monochloride
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