Organic Syntheses

Author: W. A. NOYES

XX Phthalimide Co Co C6H4< >O + Nh4Oh—> C6H4< >Nh + 2H2O

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.

Phthalimide may be recrystallized from water, but only about 4 g. of phthalimide will dissolve in a liter of boiling water. It may also be crystallized from alcohol, in which solvent it dissolves to the extent of five parts in a hundred at boiling temperature.

On a large scale, it would be advisable to collect the small amount of ammonia given off during the reaction.

If desired, the product obtained by pouring the reaction mass into the crock may be treated with hot water to soften the cake, broken up with a glass rod, transferred to a flask and boiled with water for a few minutes. This treatment, however, is quite unnecessary; for all practical purposes, the crude cake, as it is obtained, may be ground up and used directly.

3. Other Methods of Preparation

Phthalimide has been formed by heating ammonium phthalate;[1] by heating acid ammonium phthalate;[2] by passing dry ammonia over heated phthalic anhydride;[3] by treating phthalyl chloride with dry ammonia;[4] by heating phthalamide;[5] by heating phthalic anhydride with ammonium thiocyanate;[6] by heating phthalic anhydride with urea;[7] by heating phthalic anhydride with ammonium carbonate;[1b] by heating phthalic acid with nitriles;[2b] by fusing -cyanobenzoic acid;[3b] and by the action of potash on -cyanobenzaldehyde.[4b]

[1] Jahresb. 1868, 549; Ann. 19, 47 (1836); 41, 110 (1842); 42, 220 (1842); 205, 300 (1880); 215, 181 (1882).

[2] Jahresb. 1847-1848, 590.

[3] Am. Chem. J. 3, 29 (1881).

[4] Am. Chem. J. 3, 28 (1881).

[5] Ber. 39, 2278 (1906).

[6] Ber. 19, 1398 (1886),

[7] Ber. 10, 1166 (1877); Am. Chem. J. 18, 333 (1896); J. Am. Chem. Soc. 32, 116 (1910); Z. angew. Chem. 32, I, 301 (1919).

[1b] J. Am. Chem. Soc. 42, 1282 (1920).

[2b] J Am. Chem. Soc. 18, 680 (1896); 20, 654 (1898).

[3b] Rec. trav. chim. (I) 11, 93 (1892).

[4b] Ber. 30, 1698 (1897).

Of these, the first three are the only ones which need be considered as methods for the preparation of phthalimide. It was found that the third was by no means easy to bring about: dry phthalic anhydride is apparently only superficially affected by the dry ammonia, and it was difficult to introduce sufficient heat into the loose mass of crystals to cause the reaction to start.


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Chicago: W. A. NOYES and P. K. PORTER, "XX Phthalimide Co Co C6H4< >O + Nh4Oh— > C6H4< >Nh + 2H2O," Organic Syntheses, ed. Bryant Conant, James in Organic Syntheses Original Sources, accessed September 24, 2022,

MLA: NOYES, W. A., and P. K. PORTER. "XX Phthalimide Co Co C6H4< >O + Nh4Oh— > C6H4< >Nh + 2H2O." Organic Syntheses, edited by Bryant Conant, James, in Organic Syntheses, Original Sources. 24 Sep. 2022.

Harvard: NOYES, WA, PORTER, PK, 'XX Phthalimide Co Co C6H4< >O + Nh4Oh— > C6H4< >Nh + 2H2O' in Organic Syntheses, ed. . cited in , Organic Syntheses. Original Sources, retrieved 24 September 2022, from