In a
500-ml. glass-stoppered Erlenmeyer flask,
30 g. (0.2 mole) of D-xylose and
10.7 g. (0.2 mole) of ammonium chloride are dissolved in 100 ml. of distilled water. Cracked ice (100 g.) is added to this mixture, followed by
10 g. (0.2 mole) of sodium cyanide, and the solution is maintained at 0–5° for 48 hours. Powdered
barium hydroxide octahydrate (63 g., 0.2 mole) is added along with 100 ml. of water to the cyanohydrin mixture (Note
1), which is heated on a
steam bath for 2 hours with occasional stirring. The basic
barium gulonate (Note
2), which is allowed to separate overnight at 5°, is collected by filtration and washed with cold water (0°) until the washings are chloride-free. Excessive washing of the barium salt is to be avoided because of its solubility. The barium salt is suspended in 200 ml. of water, and the barium ion is precipitated quantitatively by sulfate ion (Note
3). After removal of the
barium sulfate by suction filtration, the filtrate and washings are concentrated to a colorless syrup on a steam bath in a stream of dry air (Note
4). The resultant syrup is dissolved in
50 ml. of hot ethylene glycol monomethyl ether (methyl Cellosolve), sufficient
ethyl acetate is added to incipient turbidity, and the solution is seeded with
D-gulonic-γ-lactone (Note
5). The lactone, which is allowed to crystallize overnight, is collected by suction filtration, washed with
ethanol and dried in a vacuum over at 60°. The
D-gulonic-γ-lactone (Note
6) has a melting point of
181–183° which is unchanged by recrystallization from aqueous
ethanol. The yield is
10.7–11.6 g. (
30–33%) (Note
7).