In a
1-l. three-necked flask, protected from the light and equipped with a
mechanical stirrer, an
inlet tube for the introduction of
chlorine (Note
1), and an exit tube carrying a
calcium chloride drying tube, are placed
150 ml. of dry chloroform (Note
2) and
102 g. (0.5 mole) of iodobenzene. The flask is cooled in an ice-salt mixture, and dry
chlorine (Note
3) is introduced, as rapidly as the solution will absorb it, until an excess is present (usually about 3 hours is required). The yellow, crystalline
iodobenzene dichloride is filtered with suction, washed sparingly with
chloroform, and dried in the air on filter paper. The yield is
120–134 g. (
87–94%) (Note
4) and (Note
5). The product is quite pure and may be used directly for the preparation of
iodosobenzene and
iodoxybenzene. Since
iodobenzene dichloride decomposes slowly on standing, it should not be stored indefinitely.