Weygand/Hilgetag Preparative Organic Chemistry

Cleavage of sulfur bonds 683
acid. 727 For isolation the reaction mixture is poured on ice, and the precipitated
sulfonyl chloride is separated and dried over sodium hydroxide in a
vacuum. Benzenesulfonyl chloride and its 3-chloro-4-methyl and m-nitro
derivatives, as well as /^toluene- and 1-naphthalene-sulfonyl chloride, amongst
others, have been obtained in this way.
p-Chlorobenzenesulfonyl chloride: 728 Chlorosulfuric acid (370 g) is added during about
15 min to a stirred suspension of dry sodium /7-chlorobenzenesulfonate (335 g) in chloroform
(700 ml), the temperature not being allowed to exceed 60°. The resulting thick slurry
is stirred at 55-60° for 6 h, then poured into ice-water. The organic phase is separated, washed
three times with cold water, dried over calcium chloride, and fractionated. The product
(293 g, 89%) has b.p. 140°/12 mm and m.p. 52-53°.
Preparation of many other sulfonyl chlorides from the sulfonic acids is covered in a review
by Suter. 152b
Arenesulfonic anhydrides can be obtained by removal of water from the
sulfonic acids by thionyl chloride according to directions given by Meyer
et al. 129 Phosphorus pentaoxide, 730 di-/?-tolylcarbodiimide, 731 or aryl cyanates
732 may also be used for this purpose.
/7-Toluenesulfonic anhydride: 732 Anhydrous i?-toluenesulfonic acid (3.44 g, 20 mmoles) is
heated in benzene (10 ml) with phenyl cyanate (1.2 g, 10 mmoles) at the boiling point until
the odor of cyanate has disappeared. The mixture is then cooled, phenyl carbamate (1.34 g,
98 %) is filtered off, and the solvent is removed from the filtrate in a vacuum. The residue of
/?-toluenesulfonic anhydride has m.p. 123-124° when recrystallized from 1:1 benzeneethanol,
the yield being 83 % (2.7 g). If /?-toluenesulfonic acid monohydrate (3.8 g) is used
with phenyl cyanate (3.6 g, 30 mmoles) the yield of anhydride is 77 %.
Knoevenagel and Polack 733 have given directions for the preparation of
aromatic sulfinic anhydrides by the action of acetic anhydride on a suspension
of the dry sulfinic acid in a little acetic acid. The reaction is catalysed by sulfuric
acid or a 0.1% solution of iron(in) chloride in glacial acetic acid or acetic
anhydride. Benzene-, /7-toluene-, /?-xylene-, pseudocumene-, mesitylene-, and
/?-bromo- and /Modo-benzene-sulfinic anhydride have been obtained in this
way.
6. Cleavage of the S-N bond
Cleavage of the S-N bond 734 of sulfonamides, yielding sulfonic acids, has
preparative interest when purification of the sulfonic acid by way of the
chloride is difficult and is better achieved by recrystallization of the amide
prepared from the chloride. The amide is hydrolysed in a hydrochloric acid
medium. 735 HC1
RSO2NHR' + H2O > RSO3H + R'NH2
RSO3H + H2O > RH + H2S04 (side reaction)
727 A. A. Spryskov and N. V. Aparjeva, Zh. Obshch. Khim., 20,1818 (1950); Chem. Abstr.,
44, 9367 (1950).
728 M. Kulka, /. Amer. Chem. Soc, 72, 1216 (1950).
729 H. Meyer and K. Schlegl, Monatsh. Chem., 34, 561 (1913); H. Meyer, Ann. Chem.,
433, 334 (1923); A. L. Bernoulli and H. Stauffer, Helv. Chim. Ada, 23, 640 (1940).
730 L. Field, /. Amer. Chem. Soc, 74, 394 (1952).
731 H. G. Khorana, Can. J. Chem., 31, 585 (1953).
732 D. Martin, Chem. Ber., 98, 3286 (1965).
733 E. Knoevenagel and L. Polack, Ber. Deut. Chem. Ges., 41, 3323 (1908).
734 D. Klamann and G. Hofbauer, Ann. Chem., 581, 182 (1952).
735 R. S. Schrieber and R. L. Shriner, /. Amer, Chem. Soc, 56, 1618 (1934).