Organic Syntheses, Coll. Vol. 4, p.937 (1963); Vol. 34, p.93 (1954).
To 179 g. (109 ml., 1.5 moles) of thionyl chloride (Note 1)
contained in a 250-ml. round-bottomed flask
, 42.8 g. (0.2 mole) of powdered sodium p-toluenesulfinate dihydrate2 (Note 1)
is added in portions at room temperature over a 10- to 15-minute period. A vigorous reaction occurs with the evolution of hydrogen chloride
and sulfur dioxide
. As the first portions of the sulfinate are added, the temperature of the reaction mixture rises, but it soon drops to approximately 0° as the addition proceeds (Note 2)
. The resulting reaction mixture, a clear yellow liquid containing a white opaque solid, is protected from atmospheric moisture by means of a calcium chloride drying tube
and is set aside at room temperature for 1.5–2 hours. During this time slight effervescence continues (Note 3)
and the white opaque suspended material gradually disintegrates to a finely divided translucent deposit.
The excess thionyl chloride
is removed by distillation under reduced pressure (15–20 mm.) with the bath temperature below 50°, and the last traces are eliminated by one or two evaporations under reduced pressure after the addition of 50-ml. portions of anhydrous ether (Note 4)
. The residue consists of a viscous yellow oil containing a suspension of white granular inorganic solid. The crude sulfinyl chloride
is readily dissolved by three successive treatments with portions of anhydrous ether (50, 30, and 30 ml., respectively)
which are decanted without difficulty from most of the inorganic residue (Note 5)
. Removal of the solvent by distillation at reduced pressure leaves the sulfinyl chloride
as a clear, pale, straw-yellow oil. The yield is 30–32 g.
) (Note 6)
. Distillation at reduced pressure (Note 5)
yields p-toluenesulfinyl chloride
as a deep yellow mobile oil, b.p. 113–115°/3.5 mm.
or 99–102°/0.5 mm. (Note 7)
. The yield of redistilled material is 23–26 g.
). A small quantity (2–3 g.) of a dark tarry residue remains in the distilling flask.
When smaller quantities are used the thionyl chloride
may be added to the sulfinate in one portion. After an initial rise, the temperature drops to about 0°. With larger quantities this procedure is not practicable.
If the sodium p-toluenesulfinate
is not finely powdered, reaction occurs more slowly with emission of slight crackling sounds.
If it is desired to distil the sulfinyl chloride
subsequently, any traces of suspended material must be removed by filtration of the ethereal solution through a small filter, preferably into the distilling flask. It is advantageous to concentrate the ethereal solution to a small volume before filtering since more concentrated solutions of sulfinyl chloride
have less tendency to take up moisture from the atmosphere. The filter is rinsed with a little anhydrous ether
The checkers used an inverted funnel connected to a source of dry nitrogen
to provide an inert atmosphere for the filtration. The filtration was carried out as completely as possible directly beneath the inverted funnel through which a rapid stream of nitrogen
The sulfinyl chloride
thus obtained is satisfactory for further preparative work. The checkers found that the average yield of crude material after removal of inorganic salts by filtration was about 81%
On being heated, the sulfinyl chloride
undergoes transient color changes (green), and the redistilled material may be darker in color than the pale yellow residue obtained after the removal of the ether
For distillation the checkers employed a Claisen head with a fraction cutter. Approximately 90% of the product distilled at 93–96°/1.1 mm., n23.5D 1.6004, and 10% distilled at 98–100°/1.3–1.6 mm., n23.5D 1.5998. The total yield of distilled material in two runs averaged 74%.
Arylsulfinyl chlorides have been prepared by treating the corresponding arylsulfinic acids with an excess of thionyl chloride
in the absence of solvents, either with gentle heating3,4,5,6,7,8
or at room temperature.9
The use of nearly equimolecular proportions of the reactants, and of ether
as diluent in this reaction, has been claimed10,11
to yield a cleaner product. p-Toluenesulfinyl chloride
may be obtained directly from the hydrated sodium salt of p-toluenesulfinic acid
by the action of a large excess of thionyl chloride
, and the present procedure is based on this variation.12
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