[7] Ber. 31, 2910 (1898).
The most feasible method consists in the reduction of diazonium salts with sodium sulfite. Although this method is given in several laboratory manuals, the results were not found entirely satisfactory. The present directions provide for a lengthy but essential heating of the diazonium-sulfite mixture, omit the useless zinc dust reduction, and supply exact details for preparation on a fairly large laboratory scale.
XX
PHTHALIMIDE CO CO C6H4< >O + NH4OH—> C6H4< >NH + 2H2O
CO CO
CO CO
2C<6s<H<s>4< >O + (NH4)2CO3—> 2<C6H4< >NH + CO2 + 3H2O CO CO
Prepared by W. A. NOYES and P. K. PORTER. Checked by H. T. CLARKE and J. H. BISHOP.
1. Procedure
IN a 5-l. round-bottom flask (Pyrex) is placed a mixture of 500 g. of phthalic anhydride and 400 g. of 28 per cent ammonium hydroxide. The flask is fitted with an air condenser not less than 10 mm. in diameter and is then slowly heated with a free flame until the mixture is in a state of quiet fusion at a temperature of about 300'0. It requires about one hour before all the water has gone and about one and a half to two hours before the temperature of the reaction mixture reaches 300'0 and the mixture is a homogeneous melt. It is advisable, during the heating, to shake the flask occasionally; some material sublimes into the condenser and must be pushed down with a glass rod. The hot reaction mixture is now poured out into a crock, covered with a paper to prevent loss by sublimation, and allowed to cool. The product is practically pure without further treatment, and melts at 232-235'0. The yield is 470-480 g. (94-95 per cent of the theoretical amount).
Phthalimide may also be made by using 500 g. of phthalic anhydride and 500 g. of ammonium carbonate which has been previously ground in a mortar. The subsequent procedure is the same as when aqueous ammonia is used. Frequent shaking is necessary, and the sublimed material must be occasionally pushed back into the reaction flask. About two hours are required for completion.
2. Notes
Several smaller runs of 25 g. of phthalic anhydride gave the same percentage yield.