Organic Syntheses, Coll. Vol. 2, p.573 (1943); Vol. 11, p.94 (1931).
A 3-l. three-necked flask
is equipped with a reflux condenser
, a mechanical stirrer
, a dropping funnel
, and a tube for introducing dry carbon dioxide
. Twenty-five grams (0.11 mole) of benzophenone dichloride (Note 1)
is put into the flask, the air in the flask is displaced by a stream of carbon dioxide
, and the sodium hydrosulfide
solution is added slowly (Note 2)
. A vigorous reaction, which must be controlled by cooling, takes place, and the reaction mixture becomes deep blue in color.
After the reaction mixture has stood for one-half hour, water is added and the solution is extracted with ether
. The ether
solution is dried over calcium chloride
and the ether
is distilled. The residue is distilled under reduced pressure in an atmosphere of carbon dioxide (Note 3)
boils at 174°/14 mm.
; it distils as a blue oil which, if pure and dry, forms beautiful blue crystals on cooling. The yield of crude product is 10–12.5 g.
per cent of the theoretical amount) (Note 4)
This product is approximately 75 per cent pure and is purified further by recrystallization from petroleum ether (b.p. 70–90°). The yield of purified product melting at 53–54° is 8.4–9.9 g. (42–50 per cent of the theoretical amount).
It is necessary to have an excess of the chloride present at all times in order to prevent the formation of dibenzohydryldisulfide
, due to reduction of the thioketone with the hydrosulfide. If the chloride is added to the sodium hydrosulfide
solution, a 70 per cent yield of the pure disulfide
is obtained and no thioketone is formed.
All the operations in the purification should be done very quickly and out of contact with the air as much as possible.
This preparation is referenced from:
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