Organic Syntheses, Coll. Vol. 1, p.77 (1941); Vol. 3, p.17 (1923).
In a 2-l. bottle
equipped with a mechanical stirrer
are mixed 635 g. (800 cc., 11.0 moles) of u. s. p. acetone (Note 1)
and (Note 2)
, 420 g. (400 cc., 4.0 moles) of freshly distilled benzaldehyde
boiling at 178–180°
(shaken with dilute sodium carbonate
just before distillation), and 400 cc. of water. To this mixture, 100 cc. of 10 per cent aqueous sodium hydroxide
is slowly added from a dropping funnel (Note 3)
, while the solution is stirred, and cooled by a water bath
. The rate of addition of the alkali is so regulated that the temperature remains between 25–31°. This requires from one-half to one hour. The mixture is now stirred for two and one-quarter hours at room temperature (Note 4)
. At the end of this time dilute hydrochloric acid
is added until the mixture is acid to litmus. The two layers which form are separated in a separatory funnel
. The lower aqueous layer is extracted with 100 cc. of benzene
, and the benzene
solution added to the yellow oil which formed the upper layer in the first separation. This benzene
solution is shaken with 100 cc. of water and separated.
is then removed by distilling from a steam bath
, and the residue distilled under reduced pressure (Note 5)
, any water which condenses with the forerun being separated (Note 6)
. A special distilling flask with a fractionating side arm (p. 130)
is best employed. The material which distils at 148–160° /25 mm.
, 133–143° /16 mm.
, or 120–130° /7 mm.
weighs 430–470 g.
; it solidifies to a crystalline mass on standing, and is pure enough for all practical purposes. On redistillation there is obtained 375–450 g.
per cent of the theoretical amount) of material boiling at 137–142° /16 mm.
or 123–128° /8 mm.
, which solidifies on standing to crystals which melt at 40–42° (Note 7)
and (Note 8)
acts as an irritant, and care should be taken to prevent it from coming in contact with the skin.
If the sodium hydroxide
is added too rapidly and without cooling, the mixture darkens and the yield is lowered. The rate of addition is best determined by watching the temperature of the reaction mixture.
Instead of stirring the mixture after the addition of the sodium hydroxide
, the bottle may be securely stoppered and shaken on a shaking machine for the same length of time.
The lower the pressure used in the distillation the less decomposition occurs, and the less residue is left in the distilling flask. This residue contains some dibenzalacetone
The first few cubic centimeters of the distillate have a greenish color, but the rest is light yellow. For this reason it is desirable to collect the first of the distillate separately, if a very light colored product is desired.
On exposure to air benzalacetone
gradually turns brown, especially if it is slightly impure. Pure material can be kept for months in an ordinary stoppered bottle
without changing color.
By a like procedure in which benzaldehyde
is replaced by an equivalent quantity (540 g.) of anisaldehyde
(b.p. 180–185° /18 mm.
, m.p. 72–74°
) has been obtained in a yield of 83
per cent of the theoretical amount. The distillation residue, on recrystallization from ethyl acetate
, yields 18 g.
This preparation is referenced from:
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