In a
1-l. three-necked flask, fitted with a
thermometer, a
reflux condenser, and an
inlet tube extending to the bottom of the flask and drawn out to a small opening, are placed
600 cc. of dry carbon tetrachloride,
154 g. (0.5 mole) of di-o-nitrophenyl disulfide, m.p.
193–195° (Org. Syn. Coll. Vol. I, 1941, 220), and
0.25 g. of iodine. To the upper end of the condenser is attached a glass tube which dips below the surface of a little
carbon tetrachloride contained in a test tube. A current of
chlorine, dried with
sulfuric acid, is passed into the reaction mixture, the temperature of which is maintained at 50–60°. The rate of flow of the
chlorine (about 16–17 g. per hour) is regulated so that little or no gas escapes through the
carbon tetrachloride trap. The yellow
di-o-nitrophenyl disulfide gradually disappears, and after two to two and one-half hours a homogeneous, dark yellow solution is obtained (Note
1). The warm solution is filtered from a small amount of dark residue through a warm
Büchner funnel, the flask and filter being rinsed with
30 cc. of warm carbon tetrachloride. The yellow filtrate (Note
2) is cooled to 5° and the product allowed to crystallize. The cake of crystals is broken with a rod, collected on a Büchner funnel, and drained well. The product is dried rapidly (two hours) at 50° and bottled (Note
3). This material melts at
73–74.5° and weighs
126–135 g. (
66–71 per cent of the theoretical amount). A further crop is obtained by removing the solvent from the mother liquor by distillation from a
water bath (Note
4), the dark, residual oil being poured into an
evaporating dish. The last traces of
carbon tetrachloride are removed by drying at 50°, during which process the oil crystallizes. This material melts at
67–72° and weighs
48–58 g. It is pure enough for most purposes (Note
5). The total yield is
183–184 g. (
96–97 per cent of the theoretical amount) (Note
6) and (Note
7).