(
A)
Alcoholysis of Methyleneaminoacetonitrile.—To a solution of
51.5 g. (28 cc., 0.5 mole) of 95 per cent sulfuric acid in
125 cc. of 95 per cent ethyl alcohol at 45–50°, contained in a
wide-mouthed 250-cc. conical flask, is added
34 g. (0.5 mole) of methyleneaminoacetonitrile (p. 355) (Note
1). The flask is closed with a
rubber stopper (Note
2) and vigorously shaken by hand. Solution takes place with evolution of heat, the temperature rising about 10–15° (Note
3). The liquid separates into two layers, the upper one consisting of
methylene diethyl ether; crystallization of the
aminoacetonitrile hydrogen sulfate sets in rapidly. The mixture is shaken vigorously at intervals to prevent the formation of a hard cake of crystals. After the mass has stood overnight in the
refrigerator at 0–5°, the salt is filtered off and washed with a minimum quantity (
20–25 cc.) of ice-cold alcohol. The yield is
57–62 g. (
75–81 per cent of the theoretical amount) (Note
4).
(
B)
Preparation of Glycine.—To a boiling suspension of
253 g. (0.8 mole) of barium hydroxide octahydrate in 500 cc. of water in a
1-l. beaker is added, in portions,
61.6 g. (0.4 mole) of aminoacetonitrile hydrogen sulfate at such a rate that the mixture does not froth over. The beaker is then covered with a
1-l. round-bottomed flask containing cold running water, and boiling is continued until no more
ammonia is evolved. This requires six to eight hours. The
barium is then quantitatively precipitated by the addition of exactly the necessary amount of
50 per cent sulfuric acid (Note
5). The filtrate is concentrated on a
water bath to a volume of 50–75 cc.; on chilling, crude
glycine crystallizes and is filtered off. The filtrate is again concentrated and chilled and the crystals removed. This process is continued until the final filtrate amounts to about 5 cc. The yield of crude
glycine so obtained amounts to
25–27 g. This is systematically recrystallized from water, decolorizing with
Norite and collecting the material which melts (with decomposition) at
246° (corr.) or above. Washing of the successive crops with
50 per cent ethyl alcohol is of great assistance in freeing the crystals of mother liquor. The yield of pure
glycine is
20–26 g. (
67–87 per cent of the theoretical amount).