Org. Synth. 1952, 32, 46
DOI: 10.15227/orgsyn.032.0046
2,2-DICHLOROETHANOL
[Ethanol, 2,2-dichloro-]
Submitted by C. E. Sroog and H. M. Woodburn
1.
Checked by R. S. Schreiber and C. J. Lintner, Jr..
1. Procedure
Caution! This procedure should be carried out in a good hood, and a spark-proof motor should be used.
A 1-l. three-necked flask having ground-glass joints is fitted with an efficient reflux condenser, a dropping funnel, and a mercury-sealed stirrer, and all exits are protected by drying tubes (Note 1). In the flask are placed 300 ml. of rigorously dried ether (Note 2) and 13.6 g. (0.36 mole) of pulverized lithium aluminum hydride (Note 3). After the mixture has been stirred for 15 minutes, a milky suspension is produced. A solution of 88.6 g. (0.60 mole) of dichloroacetyl chloride in 75 ml. of dry ether is added from the dropping funnel (Note 4) at a rate such as to produce gentle reflux. The process is completed in about 2.5 hours (Note 5).
Agitation is continued for 30 minutes after all the chloride has been introduced, and the excess hydride is then destroyed by the careful, dropwise addition of water to the stirred and cooled reaction mixture. The hydrolysis is accompanied by the formation of a white curdy mass of aluminum hydroxide, and the mixture has a semisolid consistency when the hydride has been completely decomposed (Note 6). With constant stirring, 500 ml. of 10% sulfuric acid is then added slowly to the mass. Stirring is continued for 30 minutes, and the solution becomes clear during this period.
The ether layer is separated, and the solvent is removed by distillation under atmospheric pressure, and the dark-colored residue is fractionated under reduced pressure through a 25-cm. column packed with glass helices. The fraction boiling at 37–38.5°/6 mm. is collected; it weighs 44–45 g. (64–65%); nD25 1.4626; d425 1.404 (Note 7).
2. Notes
1.
To prevent partial hydrolysis of the
lithium aluminum hydride, the checkers found it desirable to dry the glassware by flaming while dry
nitrogen was being swept through the apparatus.
2.
Anhydrous
ether is recommended since a solvent containing moisture will react to coat the hydride with oxides which will retard its rate of solution. The checkers used
ether dried over
sodium wire.
3.
The hydride can be pulverized rapidly and safely by breaking the large pieces with a
spatula, followed by careful crushing with a
mortar and pestle.
4.
The
acid chloride was obtained from the Eastman Kodak Company and was used without prior treatment. The submitters report
2 that
dichloroacetyl acid or
ethyl dichloroacetate may be substituted for
dichloroacetyl chloride but that the reaction appears to be smoother with the acid chloride.
5.
The acid chloride should be added slowly since the reaction appears to have a short induction period and it is undesirable to accumulate a large quantity of unreacted material.
6.
The decomposition of the hydride is accompanied by the vigorous evolution of
hydrogen. Cessation of
hydrogen formation is evidence that the hydride is completely decomposed.
7.
The following constants have been reported in the literature for
2,2-dichloroethanol:
d415 1.415;
2 d419 1.416;
nD17.3 1.4752.
3
3. Discussion
2,2-Dichloroethanol has been prepared by the reaction of
dichloroacetaldehyde with zinc dialkyls
4 and aluminum alkoxides.
3
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
dichloroacetyl acid
sulfuric acid (7664-93-9)
ether (60-29-7)
hydrogen (1333-74-0)
nitrogen (7727-37-9)
sodium wire (13966-32-0)
2,2-Dichloroethanol,
Ethanol, 2,2-dichloro- (598-38-9)
dichloroacetaldehyde (16086-14-9)
aluminum hydroxide
dichloroacetyl chloride (79-36-7)
lithium aluminum hydride (16853-85-3)
ethyl dichloroacetate (535-15-9)
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