In a
200-cc. round-bottomed flask, fitted with a
reflux condenser, are placed
50 g. (0.33 mole) of m-nitrobenzaldehyde (Note
1),
40 g. (0.48 mole) of freshly fused sodium acetate, and
70 g. (0.68 mole) of acetic anhydride. The contents of the flask are well mixed and the mixture heated in an
oil bath held at 180° for about thirteen hours. After the reaction product has been allowed to cool slightly, it is poured into 200–300 cc. of water and then filtered by suction (Note
2). After the solid has been washed several times with water, it is dissolved in a solution of
20 cc. of aqueous ammonia (sp. gr. 0.9) in about 200 cc. of water. The solution of the ammonium salt, after filtering, is poured into a solution of
15 cc. of sulfuric acid (sp. gr. 1.84) in about 200 cc. of water (Note
3). The precipitated
m-nitrocinnamic acid is filtered, redissolved in aqueous
ammonia, and again precipitated by pouring the solution into dilute
sulfuric acid (Note
4).
After the last precipitation, the
m-nitrocinnamic acid is washed with a little water and then sucked as dry as possible (Note
5). The product, which still contains considerable water, is dissolved in
250–300 cc. of boiling 95 per cent alcohol from which the
nitrocinnamic acid crystallizes on cooling. The yield is
47–49 g. (
74–77 per cent of the theoretical amount). The product is pale yellow and melts at
192–194°. If a purer product is desired, it may be recrystallized from
benzene or alcohol (Note
6).