A
5-l. three-necked round-bottomed flask equipped with a
reflux condenser, a
sealed mechanical stirrer, and a
dropping funnel is set up in a
hood and charged with
333 g. (1.50 moles) of m-nitrobenzenesulfonyl chloride (Note
1). The stirrer is started and
1033 ml. (7.5 moles) of 55–58% hydriodic acid (Note
2) is rapidly added dropwise over a period of 30–45 minutes (Note
3). After the addition is complete, the reaction mixture is stirred and refluxed on a
steam bath for 3 hours. It is then cooled to room temperature, and the dropping funnel is replaced with an open powder funnel. Solid
sodium bisulfite powder (Note
4) is added in portions until all the
iodine has been reduced, and the reaction mixture is a suspension of pale yellow
m-nitrophenyl disulfide in an almost colorless solution. The reaction mixture is filtered through a coarse-grade
sintered-glass funnel to separate the disulfide, which is washed thoroughly with warm water to remove all inorganic salts. There is obtained
210–221 g. (
91–96%) of crude
m-nitrophenyl disulfide, m.p.
81–83°. This material is purified by dissolving it in approximately
800 ml. of boiling acetone, which is filtered hot and cooled to give
170–183 g. (
74–79%) of the disulfide in the form of pale yellow prisms, m.p.
82–83°. By concentration of the mother liquor an additional
30–40 g. (
13–17%) of disulfide, m.p.
82–83°, is obtained, so that the total yield of satisfactory product is
200–210 g. (
86–91%).