Submitted by J. H. Gardner and C. A. Naylor Jr.
Checked by C. R. Noller and Carl Linn.
1. Procedure
In a
3-l. three-necked flask, provided with a
liquid-sealed mechanical stirrer, a
reflux condenser, and a
dropping funnel, are placed
500 cc. of 0.5 N sodium hydroxide solution and
32 g. (0.25 mole) of pure naphthalene. The mixture is heated to boiling, and a boiling solution of
212 g. (1.34 moles) of potassium permanganate in 1.5 l. of water is added in small portions during one and one-half hours with vigorous stirring (Note
1). After the last addition, the mixture is boiled for thirty to forty-five minutes to complete the oxidation. Any unchanged permanganate is reduced by the addition of
20 cc. of alcohol, the flask is cooled to solidify the residual
naphthalene, and the mixture is filtered.
The filtrate is acidified with
150 cc. (1.8 moles) of concentrated hydrochloric acid (sp. gr. 1.18), evaporated to 500 cc., cooled, and filtered. The filtrate is neutralized with
30 per cent sodium hydroxide solution (150–160 cc.),
50 g. (0.48 mole) of sodium bisulfite is added, and the mixture is evaporated to dryness on a
steam bath. The residue is stirred with
100 cc. of concentrated hydrochloric acid and evaporated to dryness on a steam bath. The
hydrochloric acid treatment and evaporation are repeated (Note
2).
The residue is extracted thoroughly with
benzene in a
large Soxhlet extractor (Note
3), and the
benzene extract is evaporated to dryness. The crude product is dissolved in 50 cc. of hot water, the solution filtered, and the filtrate cooled in an
ice bath with stirring (Note
4). The crystals are filtered with suction and dried in the air. The yield of slightly colored product melting at
94–95° 15–15.5 g. (
40–41 per cent of the theoretical amount).
When this material is recrystallized from 40 cc. of water with
1 g. of decolorizing carbon, and the filtrate cooled to 0°, there is obtained
14–14.5 g. of white crystals melting at
96–96.5°.
2. Notes
1. During the addition of the hot permanganate solution no external heat is applied. From time to time steam is passed through the condenser jacket to return the sublimed
naphthalene to the reaction flask.
2. The treatment with
hydrochloric acid and the evaporation are repeated in order to decompose completely the
phthalaldehydic acid bisulfite compound. Wegscheider and Bondi
1 state that it is necessary to heat the bisulfite compound on the
water bath several days with a large excess of
hydrochloric acid, but the treatment described above has been found adequate.
3. The material requires two extraction thimbles of the 45 by 125 mm. size, or four of the 30 by 75 mm. size. It is advantageous to use a
modified Soxhlet extractor of the Clausnitzer type,
2 which allows the vapor of the boiling solvent to surround the extractor tube.
4. It is essential to control carefully the volume of water used in recrystallization. The crude acid contains considerable amounts of
phthalic acid; too small a volume of water results in a contaminated product, and too large an amount causes a decided decrease in yield.
3. Discussion
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