(Chief Bee)
12-20-02 06:59
No 390996
      Purification of Thionyl Chloride
(Rated as: good read)

Purification of Thionyl Chloride

This substance is ordinarily purified by treatment with quinoline and linseed oil, a procedure that gives poor yields and difficult-to-handle residues. Pratt modified the method by using a lower aliphatic ketone in place of quinoline and sulfur in place of the linseed oil. The latter procedure has been modified herein as follows: 900 mL of crude technical thionyl chloride was refluxed for 4.5 h with 25g of flowers of sulfur and distilled rapidly through a 30-bulb Snyder column attached to an all-glass setup. A 94% yield of colored product was taken overhead. The distillate was fractionated through the 30-bulb column, about 12 h being needed to remove the colored forerun. The colorless portion was taken overhead in about two hours and distilled over no range with a thermometer that was graduated in degrees. The yield in the second step was 88% making an 82% overall yield. The product was colorless when viewed crossways in a liter graduate and very slightly yellow when viewed from the top. The still went to dryness and the residue was yellow with some black material reminiscent of organic matter. No attempts to improve the above procedure were made. The sulfur probably aids in changing the sulfuryl chloride to sulfur dioxide and sulfur chlorides. The sulfur monochloride, bp 135.6C, presumably is left behind in the first distillation and sulfur dichloride, bp 69C, is the forerun of the fractionation which gives the colorless thionyl chloride, bp 78.8C. It is probably impractical to try removing both sulfur chlorides in one distillation because of the equilibrium between sulfur monochloride on the one hand and sulfur dichloride and sulfur on the other.

Reference: JACS 68, 1380-1381 (1946)
(Hive Bee)
12-21-02 22:47
No 391512
      Purification of Thionyl Chloride
(Rated as: good read)


The sulfur-catalyst mixture is prepared by melting 400 grams of sulfur and stirring into the molten mass 8.0 grams of aluminum chloride. The mixing operation is conducted under a nitrogen atmosphere to reduce the moisture. After through mixing, the mass is allowed to cool and solidify. The cooling solidification step is also conducted under a nitrogen atmosphere. The mass is crushed into smaller pieces of a size that will allow easy entry into the port of the distilling column. Storage of the sulfur-aluminum chloride mixture is under a nitrogen blanket to prevent moisture from entering the mixture.


The equipment consists of a 500 ml three necked flask with heating mantle, agitator and attached to the center opening of the flask is a ten plate Oldershaw column with a reflux splitter and condenser attached.

600 grams of crude thionyl chloride was added to the flask. This crude thionyl chloride contained 13.80 to 16.87% sulfur chlorides (S2 Cl2 and SCl2) and 0.09% sulfuryl chloride. 30 grams of sulfur was added to the flask and 124.8 grams of the 2% AlCl3 -sulfur catalyst -product from 1.)- was added to the top of the distillation column, as needed. No mechanical reflux was employed but internal reflux was observed due to column cooling. 282 grams of distillate was collected.

Reference: Patent US4337235

Other Patents describing the purification of this compound:


"Turn on, Tune in and Drop Out"
01-19-03 00:02
No 399494
      A Perfect Method for Purification  Bookmark   

1) Add 10% by weight triphenyl phosphite (PhO)3P to your thionyl choride.
2) Distill as usual, disposing of the forerun.

You will get water-white, clear thionyl chloride.


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