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).
[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.