Organic Syntheses, Coll. Vol. 6, p.10 (1988); Vol. 50, p.3 (1970).
is toxic and should be handled in a hood
. Anhydrous hydrazine
is extremely reactive with oxidizing agents (including air) and should always be prepared and used behind a protective screen.
A. Acetone azine
. A 500-ml., round-bottomed flask
containing 145 g. (183 ml., 2.50 moles) of acetone (Note 1)
is fitted with a mechanical stirrer (Note 2)
and a dropping funnel
and cooled in an ice bath
. With vigorous stirring, 65.5 g. (1.31 moles) of 100% hydrazine hydrate (Note 1)
is added at such a rate that the temperature is maintained below 35°. The addition takes 20–30 minutes. The mixture is stirred for an additional 10–15 minutes before 50 g. of potassium hydroxide pellets
is added with vigorous stirring and continued cooling (Note 3)
. The upper liquid layer is separated and allowed to stand over 25 g. of potassium hydroxide pellets
for 30 minutes, with occasional swirling (Note 4)
. After filtration, the liquid is further dried with two successive 12.5-g. portions of potassium hydroxide
. Distillation gives 120–126 g.
) of almost colorless acetone azine
, b.p. 128–131°
1.4538 (Note 5)
A mixture of 112 g. (1.00 mole) of acetone azine
and 32 g. (1.0 mole) of anhydrous hydrazine
is placed in a 300-ml. round-bottomed flask
fitted with a reflux air condenser
and drying tube, and kept at 100° for 12–16 hours.
(Caution! This reaction and the subsequent distillation should be carried out behind a protective screen.)
The crude product is then distilled rapidly through a water-cooled condenser
, and the colorless fraction boiling at 122–126° is collected, nD22
1.4607 (Note 7)
, yielding 111–127 g.
, (Note 7)
and (Note 8)
) of essentially pure acetone hydrazone (Note 9)
A Hershberg stirrer made of Nichrome wire
is most efficient for aiding dissolution of the potassium hydroxide
added after azine formation is complete.
The dissolution of the potassium hydroxide
is strongly exothermic. A small proportion may remain undissolved.
A lower, aqueous phase may form at this stage, but the product is easily decanted from it.
The purity is 95–98% by this method.3
The purity is lower (85–95%) by an alternative procedure4
which requires separation of the hydrazine
and alkaline phases above 60°; with the latter method the submitters found that a frequent problem was the solidification of the lower phase in the separating funnel
, and in one case a very serious fire
occurred during the transfer of the hot (ca.
100°) mixture to the separating funnel.
The forerun contains hydrazine
; material boiling above 126° contains much acetone azine
. With a slow rate of distillation, disproportionation occurs and the yield of acetone hydrazone
is reduced. If the forerun and material boiling above 126° are combined and reheated at 100° for 12–16 hours, they give more acetone hydrazone
on redistillation. With further repetitions of this procedure, the yield is almost quantitative.
The highest yields were obtained in cases where the anhydrous hydrazine
was treated with barium oxide
for several hours before use.
The hydrazone should be used as soon as possible. If it is stored, care must be taken to exclude moisture, which catalyzes disproportionation to hydrazine
and acetone azine
Even in the absence of moisture it disproportionates slowly at room temperature and so should be redistilled immediately before use. Old samples can be regenerated fairly satisfactorily by reheating them for 12–16 hours at 100° before redistillation, but there is always some irreversible decomposition to high-boiling products during storage.
The procedure for acetone azine
is essentially that of Curtius and Thun.5
The method for acetone hydrazone
is adapted from that of Staudinger and Gaule.8
The hydrazone has been prepared directly from acetone
, but this is much less satisfactory.6
is produced in good yield by the method described, but an inferior product is obtained without the precautions noted. The compound is used for the preparation of 2-diazopropane
This preparation is referenced from:
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