Org. Synth. 1962, 42, 59
DOI: 10.15227/orgsyn.042.0059
ETHYLENE SULFIDE
Submitted by Scott Searles, Eugene F. Lutz, High R. Hays, and Harley E. Mortensen
1.
Checked by Melvin S. Newman and Bernard C. Ream.
1. Procedure
Into a 500-ml., two-necked, round-bottomed flask equipped with a thermometer (Note 1) and leading to a condenser equipped with a distillation head and a receiver is placed 145 g. (1.5 mole) of potassium thiocyanate (Note 2). The system is evacuated to about 1 mm., and the flask is heated with a free flame until the temperature of the molten salt is in the 165–175° range (Note 3). After the flask has been heated for 15 minutes, it is cooled to room temperature and 88 g. (1.0 mole) of ethylene carbonate (Note 4) is added. The apparatus is reconnected and the receiver protected with a calcium chloride tube.
The reaction flask is slowly heated by means of a sand bath, and the receiver is cooled in a Dry Ice-acetone bath. When the temperature in the fused potassium thiocyanate layer reaches 95°, reaction occurs. Ethylene sulfide distils and is collected in the receiver. Heating is continued for about 3 hours at 95–99° (Note 6). The distillate amounts to 41–45 g. (68–75%) (Note 7) and is sufficiently pure to be used directly (Note 8).
2. Notes
1.
The thermometer may be inserted through a
neoprene stopper in one neck or into a
suitably designed thermometer well.
2.
J. T. Baker's analytical grade was used.
3.
The purpose of this operation is to ensure dryness, as
potassium thiocyanate is hygroscopic. The presence of even small amounts of water is detrimental to the yield. The initially colorless salt melts to a blue liquid. On cooling, this solidifies to a colorless solid.
It has been reported that this procedure is more easily reproduced when the potassium thiocyanate is heated to ca. 100–110° at 0.1 mm. so that the salt does not melt, and a larger surface is available for reaction (Nelson N. Schwartz, private communication).
4.
Ethylene carbonate obtained from the Eastman Kodak Company or the Jefferson Chemical Company was vacuum distilled and the fraction, b.p.
125°/10 mm., was used.
5.
It has been reported that an
oil bath may be used to provide greater uniformity of heating (Nelson N. Schwartz, private communication).
6.
Differences in the rate of heating and time of heating cause small changes in the yield of
ethylene sulfide obtained. If the time of heating is reduced and the rate of heating increased, the yield drops somewhat. For many purposes the saving in time offsets the higher yield obtained under optimum conditions. The submitters have obtained yields in the
81–87% range.
7.
This product can be stored at room temperature for several weeks without polymerization. On distillation, pure
ethylene sulfide, b.p.
54.0–54.5°,
nD20 1.4960, is obtained.
8.
For example, this product is suitable for reaction with amines.
2
3. Discussion
Ethylene sulfide has been prepared by the reaction of
ethylene oxide with aqueous
potassium thiocyanate;
2,3 by the reaction of
2-chloroethyl mercaptan with
aqueous sodium bicarbonate;
4 by the reactions of
2-chloroethylthiocyanate5 and
1,2-dithiocyanoethane6 with
alcoholic sodium sulfide; and by the thermal decomposition of
monothiolethylene carbonate.
7
4. Merits of Preparation
The advantage of the present procedure is the easy availability at low expense of the starting material,
ethylene carbonate.
8 Its advantages over the other methods are high yields and degree of purity of the product, combined with greater simplicity of procedure.
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
monothiolethylene carbonate
sodium bicarbonate (144-55-8)
Ethylene oxide (75-21-8)
sodium sulfide (1313-82-2)
potassium thiocyanate (333-20-0)
Ethylene sulfide (420-12-2)
ethylene carbonate (96-49-1)
2-chloroethyl mercaptan
2-chloroethylthiocyanate (928-57-4)
1,2-dithiocyanoethane
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