Preparation of Glycine

Subject: Preparation of Glycine Thu Jul 28, 2011 1:53 pm

Glycine (CAS NO.56-40-6)e is manufactured by treating chloroacetic acid with ammonia industrially
ClCH2COOH + 2 NH3 → H2NCH2COOH + NH4Cl
It also can be produced via the Strecker amino acid synthesis.

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. 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).