Org. Synth. 1936, 16, 68
Submitted by J. H. Gardner and C. A. Naylor Jr.
Checked by C. R. Noller and Carl Linn.
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°.
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.
The treatment with hydrochloric acid
and the evaporation are repeated in order to decompose completely the phthalaldehydic acid bisulfite
compound. Wegscheider and Bondi1
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.
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
which allows the vapor of the boiling solvent to surround the extractor tube.
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.
has been prepared by the hydrolysis of 2-bromo- or 2-chlorophthalide
of o-trichloromethylbenzal chloride
of o-cyanobenzal chloride
and of o-dichloromethylbenzoyl chloride
by the ozonization of naphthalene
by the alkaline oxidation of naphthalene
followed by the preparation and decomposition of the aniline condensation product10
or the bisulfite compound1, 11 of phthalonic acid
; and by carbonating the reaction product of o-chlorobenzaldehyde and sodium
Detailed directions for the preparation of phthalaldehydic acid
by bromination of phthalide
and hydrolysis of the bromination product are given in Volume 23 of this series.
This preparation is referenced from:
Chemical Abstracts Nomenclature (Collective Index Number);
2-bromo- or 2-chlorophthalide
hydrochloric acid (7647-01-0)
sodium hydroxide (1310-73-2)
potassium permanganate (7722-64-7)
sodium bisulfite (7631-90-5)
decolorizing carbon (7782-42-5)
phthalic acid (88-99-3)
Phthalaldehydic acid (119-67-5)
phthalaldehydic acid bisulfite
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