^{A bottle of freshly prepared levulinic acid from paper mill sludge}

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1. Procedure

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).


2. Notes

1. 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.
2. 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.

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A good yielding procedure is found in Patent US5859263, which prepares levulinic acid from starch in a reactive extrusion process with yields of about 48% which is about 70% of theoretical.



Reduction of levulinic acid

Reduction of levulinic acid first yields 4-hydroxyvaleric acid, which, as the free acid, lactonizes readily to gamma-valerolactone (lactone of 4-hydroxyvaleric acid). The sodium salt of gamma-hydroxyvaleric acid can be obtained, as described by Rhodium in:

Sodium 4-Hydroxyvalerate, a Novel GHB Analog
../rhodium /4-methyl-ghb.html

Levulinic acid has been reduced to gamma-valerolactone by means of:

- sodium in alcohol
J. Am. Chem. Soc. 48, 3163-65 (1926);

- sodium amalgam
J. Gen. Chem. USSR 9, 924-931 (1939); C.A. 34, 368;

- sodium borohydride
J. Am. Chem. Soc. 71, 122-125 (1949);

- lithium borohydride
J. Am. Chem. Soc. 71, 3245-46 (1949);

- aluminium amalgam
Bul. Sci. Fakultat Terkult. Kyushu Imp. Univ. Fukuova 11, 86-90 (1944); C.A. 43, 5367





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