Organic Syntheses, Coll. Vol. 1, p.283 (1941); Vol. 7, p.42 (1927).
In a 5-l. round-bottomed flask
equipped with a mechanical stirrer
are mixed 385 g. (335 cc., 3.8 moles) of 95 per cent furfural (p. 280) (Note 1)
and 3 l. of water. Then 500 g. (630 cc., 8.6 moles) of acetone (Note 1)
is added. The mixture is stirred and cooled to 10° and to it is added 75 cc. of 33 per cent sodium hydroxide
solution, whereupon some heat is generated. Without cooling, the stirring is continued for four hours. At the end of this time 10 per cent sulfuric acid is added until the mixture is acid to litmus (about 350 cc.) (Note 2)
. The two layers which have formed are separated and the upper aqueous layer is distilled (Note 3)
under ordinary pressure until the distillate no longer forms two layers.
The bottom layer of this distillate is added to the original lower layer and distilled under reduced pressure from a 1-l. modified Claisen flask (p. 130)
provided with an air condenser
and heated in an oil bath
. The receiving flask
is placed in a large funnel
connected with the drain. A stream of cold water is run over the receiver. When a solid appears in the receiver, distillation is interrupted, the liquid distillate is discarded, and the distillation is continued. The product which distils at 114–118°/10 mm.
) (Note 4)
weighs 310–340 g.
per cent of the theoretical amount, based on the furfural
used). The yellow crystals melt at 37–39°
and when melted show a sharp freezing point of 37° (Note 5)
Commercial chemicals were used. The use of purer chemicals, including furfural
distilled over a 2° range under diminished pressure, gives no higher yield, but the product is lighter colored, although the boiling point and melting point are the same as with the crude materials.
Some commercial grades of acetone
have a markedly deleterious effect on the yield of furfuralacetone
(F. N. Peters, private communication). Accordingly, it is recommended that acetone
of reasonably high purity be used.
When the alkali is neutralized, the mixture loses its milky appearance and forms definite layers.
The distillation of the water layer may be omitted, since it yields only 10–20 g.
of the product.
A large residue of higher-boiling material remains in the flask. This residue contains much difurfuralacetone
, the formation of which takes place to a considerable extent in spite of the large excess of acetone
The highest melting point recorded in the literature is 39–40°
. The crystals gradually become reddish on standing even in the dark. This change is much slower when freshly distilled furfural
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