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 o-cyanobenzoic acid;[3b] and by the action of potash on o-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).