(
A)
Preparation of Sodium Cyanoacetate Solution.—In a
3-l. round-bottomed flask is placed
250 g. (2.65 moles) of monochloroacetic acid. To this are added 100 cc. of water and
375 g. (1.3 moles) of crystalline sodium carbonate (decahydrate) (Note
1), the mixture being gently warmed. The neutralization is completed by adding
sodium carbonate solution using litmus paper as an indicator. The flask is transferred to the
hood, and a solution of
130 g. (2.65 moles) of sodium cyanide in 250 cc. of warm water is added in two approximately equal portions, waiting after the first addition until no further evolution of heat occurs, or the mixture ceases to boil. The cooled solution is neutralized with
hydrochloric acid, using methyl orange as an outside indicator. The solution is then diluted with water to 1 l. and filtered; it should be of a light straw color. It can be kept for long periods of time in a
stoppered bottle, although the color deepens somewhat.
(
B)
Condensation with Benzaldehyde.—To
400 cc. (1.06 moles) of the sodium cyanoacetate solution is added a solution of
5 g. (0.13 mole) of sodium hydroxide in 400 cc. of water. The resulting alkaline solution is warmed to 40° and treated with
100 g. (0.94 mole) of benzaldehyde which has been shaken with
sodium carbonate solution and distilled under reduced pressure. The
benzaldehyde dissolves after vigorous shaking for a few minutes. After standing one hour, during which time some of the
sodium cyanophenylacrylate crystallizes (Note
2), the mixture is acidified with concentrated
hydrochloric acid until acid to litmus and 40 cc. additional concentrated acid added, and the whole is shaken vigorously. After another hour, the crystalline
cyanophenylacrylic acid is filtered on a
Büchner funnel, washed thoroughly with cold water, and dried in a
steam oven. It is then shaken with
100 cc. of benzene, filtered on a Büchner funnel, and further washed with
50 cc. of benzene and dried. The yield of product melting at
178–179° is
105–115 g. (
65–70 per cent of the theoretical amount).
This product may have a slight pinkish color, which can be removed by recrystallization from
740 cc. of alcohol or 10 l. of hot water. The recovery is about
57 per cent from alcohol and
92 per cent from water (Note
3). The melting point remains unchanged.