Submitted by H. H. Hatt
Checked by W. W. Hartman and W. D. Peterson.
1. Procedure
(
A)
Benzalazine.—In a
5-l. round-bottomed flask, provided with a
stout glass mechanical stirrer, are placed
240 g. (1.85 moles) of powdered hydrazine sulfate (Org. Syn. Coll. Vol. I, 1941, 309), 1.8 l. of water, and
230 cc. (207 g., 3.4 moles) of 28 per cent aqueous ammonia (sp. gr. 0.90). The mixture is stirred, and, when the
hydrazine sulfate has dissolved,
440 cc. (460 g., 4.35 moles) of benzaldehyde (Note
1) is added from a
separatory funnel during the course of four to five hours (Note
2). After the mixture has been stirred for a further two hours, the precipitated
benzalazine is filtered with suction, washed with water, and pressed thoroughly on a
Büchner funnel. The product is dissolved in
800 cc. of boiling 95 per cent ethyl alcohol, and, on cooling, the azine separates in yellow needles melting at
92–93°. The yield is
350–360 g. (
91–94 per cent of the theoretical amount); an additional
10–15 g. of less pure material can be isolated from the mother liquors. The azine is freed of
ethyl alcohol by drying in a
vacuum desiccator over
calcium chloride.
(
B)
Methylhydrazine Sulfate.—
Two hundred grams (0.96 mole) of benzalazine,
350 cc. of dry, thiophene-free benzene, and
100 cc. (133 g., 1.05 moles) of methyl sulfate (Note
3) are mixed in a
3-l. round-bottomed flask, provided with a
reflux condenser bearing a
calcium chloride tube. The mixture is heated continuously, with occasional shaking, on a
water bath to gentle refluxing for five hours. The mixture is cooled, and the solid addition product is decomposed by adding 600 cc. of water and shaking until all the solid material has disappeared. The
benzene and
benzaldehyde are removed by steam distillation; the residual liquor, after cooling, is treated with
15–20 cc. of benzaldehyde and left overnight. The resin and
benzalazine are separated by filtration (Note
4).
The filtrate is evaporated under reduced pressure on a water bath until a semi-crystalline mass remains; this is further desiccated by evaporating twice under reduced pressure with
50-cc. portions of absolute ethyl alcohol. The resulting crystalline cake is crushed with
50 cc. of absolute ethyl alcohol, filtered, and the process repeated. The white, crystalline product is almost pure
methylhydrazine sulfate and contains very little
hydrazine sulfate. After drying in a vacuum desiccator over
calcium chloride, the yield is
105–110 g. (
76–80 per cent of the theoretical amount). For purification, the sulfate is dissolved in about
250 cc. of boiling 80 per cent ethyl alcohol, and any undissolved material (chiefly
hydrazine sulfate) is filtered. On cooling, the
methylhydrazine sulfate separates in white plates, which are filtered with suction and washed with a little absolute
alcohol. After drying over
calcium chloride, the first fraction, m.p.
141–142°, weighs
70–75 g. (
51–54 per cent of the theoretical amount) (Note
5).
2. Notes
2. The mixture is stirred vigorously during the reaction, and one or two
stout glass rods are clamped in the flask to act as baffles and to break up the lumps of
benzalazine.
3.
Methyl sulfate is extremely toxic. It should not be spilled; neither should the vapor be inhaled.
Ammonia is a specific antidote.
4. Unreacted
hydrazine sulfate is removed by conversion to
benzalazine. The filtrate should not give an appreciable precipitate when mixed with
5 cc. of benzaldehyde and left for four hours.
5. From the mother liquors about
12 g. of less pure material, m.p.
133–136°, can be recovered.
3. Discussion
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