In a carefully cleaned
500-ml. Erlenmeyer flask, covered with a
watch glass, are placed
49.4 g. (0.35 mole) of N,N-dimethylcyclohexylmethylamine (Note
1),
39.5 g. (0.35 mole) of 30% hydrogen peroxide, and
45 ml. of methanol. The homogeneous solution is allowed to stand at room temperature for 36 hours. After 2 and 5 hours
hydrogen peroxide (39.5-g. portions each time) is added (Note
2), (Note
3). The excess
hydrogen peroxide is destroyed by stirring the mixture with a small amount of
platinum black (Note
4) until the evolution of
oxygen ceases. The solution is filtered into a
500-ml. round-bottomed flask and concentrated at a bath temperature of 50–60° (Note
5), a
water aspirator being used initially and an
oil pump finally, until the amine oxide hydrate solidifies. A
Teflon-covered stirring bar is introduced into the flask, which is then connected by a
20-cm. column to a
trap (reversed to avoid plugging) cooled in Dry Ice-acetone. The flask is heated in an
oil bath to 90–100°, and the apparatus is evacuated to a pressure of ca. 10 mm. with stirring of the liquefied amine oxide hydrate. When the content of the flask resolidifies, the temperature of the oil bath is raised to 160°. The amine oxide decomposes completely within about 2 hours at this temperature. Water (100 ml.) is added to the contents of the trap. The olefin layer is removed with a
pipette and washed with two 5-ml. portions of water, two
5-ml. portions of ice-cold 10% hydrochloric acid (Note
6), (Note
7), and one
5-ml. portion of 5% sodium bicarbonate solution. The olefin is cooled in a
Dry Ice-acetone bath and filtered through glass wool (Note
8). Distillation over a small piece of
sodium through a
semimicro column2 yields
26.6–29.6 g. (
79–88%) of
methylenecyclohexane, b.p.
100–102° (Note
9),
n25D 1.4474 (Note
10).
The aqueous layer is combined with the two neutral aqueous extracts and acidified by addition of
45 ml. of concentrated hydrochloric acid. The solution is concentrated under reduced pressure at 60–70° until no more distillate comes over. The residue, which solidifies on cooling, is dried in a
vacuum desiccator over
potassium hydroxide pellets to yield
30.7–32.7 g. (
90–96%) of crude
N,N-dimethylhydroxylamine hydrochloride, m.p.
103–106° (
sealed tube). Crystallization from
40 ml. of isopropyl alcohol gives
26.6–30.7 g. (
78–90%) of the pure hydrochloride, m.p.
106–108° (sealed tube).