Submitted by S. Smiles and Jessie Stewart.
Checked by Henry Gilman and F. Schulze.
1. Procedure
In a
500-cc. round-bottomed flask, fitted with a
mechanical stirrer, is placed
290 g. (165 cc., 2.49 moles) of chlorosulfonic acid (Note
1). The flask is surrounded by a
cooling bath and cooled with running water to about 12–15°. To the
chlorosulfonic acid is added gradually
67.5 g. (0.5 mole) of acetanilide. This requires about fifteen minutes if the temperature is maintained at approximately 15°. Since large volumes of
hydrogen chloride are evolved, the reaction should be conducted in a
good hood, or a
gas absorption trap (Fig. 7 on p. 97) might be used. After all the
acetanilide has been added, the mixture is heated to 60° for two hours to complete the reaction (Note
2).
The sirupy liquid is poured slowly, with stirring (Note
3), into 1 kg. of ice to which just enough water has been added to make stirring easy. This decomposition of the excess
chlorosulfonic acid should be carried out in the hood. The solid
sulfonyl chloride which separates is collected on a
suction funnel (Note
4) and washed with water. The yield of crude material is
90–95 g. (
77–81 per cent of the theoretical amount based on the
acetanilide).
This crude material may be used directly in many preparations such as
p-acetaminobenzenesulfinic acid (p. 7). If a pure product is desired, the crude material is dried by pressing on a
porous plate and then crystallized from dry
benzene. The
acid chloride is slightly soluble in
benzene, and only 1.5 to 2 g. will dissolve in
100 cc. of hot benzene. On cooling, about
75 per cent of the material separates from the
benzene in thick, colorless prisms melting at
149° (Note
5).
2. Notes
1. The
chlorosulfonic acid should be freshly distilled. Smaller amounts of this reagent may be used without reducing the yield or affecting the quality of the product. However, with smaller amounts the time required for the reaction must be increased. Thus, if
175 g. (1.5 moles) of chlorosulfonic acid is used with
67.5 g. (0.5 mole) of acetanilide, an additional hour of heating is required to obtain the yields mentioned above.
2. The
hydrogen chloride which is liberated during the reaction fills the mixture with tiny bubbles. When these disappear the reaction is complete.
3. Mechanical stirring is most convenient but not necessary.
4. A rather
large suction funnel (125 mm. or more) should be used in the filtration as the
sulfonyl chloride has a tendency to clog the filter.
5. The purification is the least satisfactory part of the preparation. The material must not be heated while water is still present, or excessive decomposition will occur. As the
sulfonyl chloride is only slightly soluble in hot
benzene, it is inconvenient to crystallize more than a small amount at a time. The crude product does not keep well and must be used at once. After recrystallization it may be kept indefinitely.
3. Discussion
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