Organic Syntheses, Coll. Vol. 2, p.11 (1943); Vol. 19, p.4 (1939).
In a 1-l. Erlenmeyer flask
provided with a mechanical stirrer
are placed 75 g. (1 mole) of glycine (Org. Syn. Coll. Vol. I, 1941, 298)
and 300 cc. of water. The mixture is stirred vigorously until the glycine
is almost completely dissolved, when 215 g. (2 moles) of 95 per cent acetic anhydride (Note 1)
is added in one portion. Vigorous stirring is continued for fifteen to twenty minutes, during which time the solution becomes hot and acetylglycine
may begin to crystallize. The solution is placed in the refrigerator (Note 2)
overnight to effect complete crystallization. The precipitate is collected on a Büchner funnel
, washed with ice-cold water, and dried at 100–110°. This product weighs 75–85 g.
and melts at 207–208°
. The combined filtrate and washings are evaporated to dryness under reduced pressure on a water bath
at 50–60°. The residue on recrystallization from 75 cc. of boiling water yields a second fraction, of 20–30 g.
, which melts at 207–208°
after being washed with ice-cold water and dried at 100–110°. An additional 4–6 g.
of only slightly less pure product may be obtained from the mother liquor by concentration. The total yield is 104–108 g.
per cent of the theoretical amount) (Note 3)
The refrigerator used by the checkers maintained a temperature of 5–7°.
The method may be employed to acetylate most α-amino acids with only slight modifications depending upon the solubility of the particular amino acid. When optically active amino acids are acetylated, there is little or no racemization.1
This preparation is referenced from:
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