Checked by R. T. Arnold and George P. Scott.
1. Procedure
In a
1-l. round-bottomed flask is placed a mixture of
204.3 g. (1 mole) of finely divided phosphorus pentachloride and
132.8 g. (0.4 mole) of the disodium salt of naphthalene-1,5-disulfonic acid which has been dried previously at 140° for 48 hours (Note
1). The flask is provided with an
air condenser which is fitted at the top with a calcium chloride drying tube. It is then placed in an
oil bath which is heated to 110°, and the mixture is maintained at that temperature for 1 hour. The condenser is removed for brief intervals now and then during the heating period, and the reactants are stirred by means of a
glass rod. At the end of the heating period, the product is a thick paste.
The flask and contents are placed on a
steam cone and heated for 2 hours under vacuum (furnished by a
water aspirator) (Note
2) in order to remove the
phosphorus oxychloride formed in this process as well as most of the unreacted
phosphorus pentachloride. The dry cake is pulverized in a
mortar and transferred to a
4-l. beaker. To this is added 750 ml. of distilled water and
2 l. of chloroform. The mixture is placed on a
steam bath, heated to boiling, and stirred vigorously until nearly all the solid dissolves. By means of a
separatory funnel the layers are separated while still hot. The
chloroform solution is again heated to boiling and filtered through a large fluted filter into an
Erlenmeyer flask.
After sufficient
chloroform has been evaporated to give a solution volume approximating 250 ml., the solution is cooled in an
ice bath and the crystalline product collected on a filter. By further concentration of the mother liquor, an additional quantity of
naphthalene-1,5-disulfonyl chloride is obtained. A total yield of
85–115 g. (
65–88%) of recrystallized material results; m.p.
181–183°.
2. Notes
1. The powdered solids should be thoroughly mixed before heating. This may be done by inserting a
rubber stopper into the neck of the reaction flask and shaking vigorously for about 2 minutes. However, an appreciable pressure develops in the flask and care must be taken in removing the stopper.
2. The reaction flask should be connected to the receiver by a tube of large bore and equipped, preferably, with ground-glass fittings. Two traps between the receiver and the aspirator are desirable to assure no contact between the phosphorus chlorides and water.
3. Discussion
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