Organic Syntheses, Coll. Vol. 1, p.335 (1941); Vol. 9, p.50 (1929).
To a solution of 500 g. (1.46 moles) of cane sugar (Note 1)
in 1 l. of water in a 2-l. flask
is added 250 cc. of concentrated hydrochloric acid
(sp. gr. 1.16). The flask is heated on a steam bath
for twenty-four hours, during which time considerable carbonization takes place. The black solid is filtered off with suction and washed with 300 cc. of water. The filtrate is placed in a large evaporating dish
on a steam bath and allowed to evaporate overnight. The black solid residue obtained on the following morning is ground to a powder and placed in a folded filter paper of 34-cm. diameter
. This is placed in a 25-cm. funnel
fitted with a water-cooled 12-l. flask
as described on p. 375
. The solid is extracted with 500 cc. of ether
for six to eight hours. The ether is distilled and the residue (Note 2)
fractionated under reduced pressure. The fraction distilling at 150–160°/15 mm.
or 135–140°/10 mm.
forms a rather dark liquid which does not completely solidify on cooling.
On redistillation under reduced pressure a fraction boiling over a range of not more than 2° (e.g., 137–139°/10 mm.) is obtained with very little loss; this fraction solidifies almost completely at 30°. The yield is 72–76 g. (21–22 per cent of the theoretical amount).
Equally good results may be obtained with starch
; the mixture however, must be warmed more slowly as it is apt to foam at the outset.
When larger quantities of levulinic acid
are to be prepared it has been found by the checkers
to be more convenient to fractionally distil the first filtrate under reduced pressure, without evaporating to dryness and extracting with ether. In this case a considerable quantity of tarry residue remains in the distilling flask
. The yields are equally good.
The only practical methods for preparing levulinic acid
depend upon the action of mineral acids upon carbohydrates, a reaction discovered by Grote and Tollens,1
who heated cane sugar
with dilute sulfuric acid
. The procedure described is essentially that of Conrad,2
descriptions of which frequently have appeared3
in the subsequent literature. Improved yields have been reported4
by digesting sucrose
under pressure for one hour with dilute hydrochloric acid
at 162° in the presence of water vapor. The use of distillation under reduced pressure was suggested by Kent and Tollens.5 Levulinic acid
can also be prepared from starch6
and from glucose7
by the action of hydrochloric acid
, and from furfuryl alcohol or hydroxymethylfurfural
by the action of dilute mineral acids.8
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