Organic Syntheses, CV 5, 813
Submitted by Bernhard Raecke and Hubert Schirp
1.
Checked by B. C. McKusick and P. E. Aldrich.
1. Procedure
A solution of
66.5 g. (1.01 moles) of 85% potassium hydroxide in 300 ml. of water in an
800-ml. beaker is heated to 60–70°, and
100 g. (0.505 mole) of commercial 1,8-naphthalic anhydride (Note
1) is stirred in. The pH of the resultant deep-brown solution is adjusted to a value of 7 (Note
2) with
6N hydrochloric acid and 3
N potassium hydroxide. It is treated with
10 g. of decolorizing carbon and filtered. This operation is repeated. The filtrate is concentrated in a
1.5-l. beaker on a
steam bath to about 180 ml. The concentrate is cooled to room temperature,
800 ml. of methanol is added with vigorous stirring by hand, and the mixture is cooled to 0–5°. The precipitated
dipotassium naphthalate is separated by filtration, washed with
150 ml. of methanol, and dried in a
vacuum oven at 150°/150 mm. The dried cream-colored salt weighs
130–135 g. (
88–92%).
A mixture of
100 g. of dipotassium naphthalate and
4 g. of anhydrous cadmium chloride2 is ground in a ball mill for 4 hours. The mixture is placed in a
0.5-l. autoclave (Note
3) and (Note
4) that can be rocked, rolled, or shaken. The autoclave is evacuated, for
oxygen lowers the yield of the product. The autoclave is then filled with
carbon dioxide to a pressure of about 30 atm. The agitated autoclave is heated to an internal temperature of 400–430° in the course of 1–2 hours and is maintained at this temperature for 1.5 hours. The pressure rises to about 90 atm. in the course of the heating (Note
4).
The autoclave is cooled to room temperature, and the
carbon dioxide is bled off. The solid reaction product is taken from the autoclave, pulverized, and dissolved in 1 l. of water at 50–60°.
Ten grams of decolorizing carbon is added, and the mixture is stirred well and filtered to remove
cadmium salts and carbon. The filtrate is heated to 80–90° and acidified with concentrated
hydrochloric acid to pH 1 (Note
5).
2,6-Naphthalenedicarboxylic acid precipitates. It is separated from the hot mixture by filtration. It is then suspended in 500 ml. of water at 90–95° (Note
5), separated by filtration, and washed successively with 300 ml. of water,
300 ml. of 50% ethanol, and
300 ml. of 90% ethanol. After being dried at 100–150°/150 mm. in a vacuum oven, the
2,6-naphthalenedicarboxylic acid weighs
42–45 g. (
57–61%). It decomposes on a heated block at 310–313°.
2. Notes
1. Suitable
1,8-naphthalic anhydride, m.p. 274–275°, is obtainable from Coaltar Chemicals Corp., 420 Lexington Ave., New York, N. Y.
2.
Bromothymol blue or commercial universal indicator pH paper (graduated in 0.2-pH units) may be used as external indicators.
3. A
150-ml. shaking Hastelloy-C autoclave, manufactured by the Haynes Stellite Division of Union Carbide Co., Kokomo, Indiana, was used by the checkers. The approximate composition of the alloy is: Cr, 15.5–17.5%; Mo, 16–18%; Fe, 4.5–7%; W, 3.7–4.75%; and the remainder, Ni. Because their autoclave had only three-tenths the capacity of that used by the submitters, the checkers used three-tenths the quantities of materials given here.
4. The line to the pressure gauge tends to become clogged during the reaction.
5. Heat conduction in the heavy slurry that is formed is poor, and bumping may occur if the mixture is overheated. Efficient mechanical stirring aids this operation.
3. Discussion
The present method for preparing aromatic dicarboxylic acids has been used to convert
phthalic or isophthalic acid to
terephthalic acid (
90–95%);
2,2'-biphenyldicarboxylic acid to
4,4'-biphenyldicarboxylic acid;
3,4-pyrroledicarboxylic acid to
2,5-pyrroledicarboxylic acid; and
2,3-pyridinedicarboxylic acid to
2,5-pyridinedicarboxylic acid.
7 A closely related method for preparing aromatic dicarboxylic acids is the thermal disproportionation of the potassium salt of an aromatic monocarboxylic acid to an equimolar mixture of the corresponding aromatic hydrocarbon and the dipotassium salt of an aromatic dicarboxylic acid. The disproportionation method has been used to convert
benzoic acid to
terephthalic acid (
90–95%); pyridinecarboxylic acids to
2,5-pyridinedicarboxylic acid (
30–50%);
2-furoic acid to
2,5-furandicarboxylic acid;
2-thiophenecarboxylic acid to
2,5-thiophenedicarboxylic acid; and
2-quinolinecarboxylic acid to
2,4-quinolinedicarboxylic acid.
7 One or the other of these two methods is often the best way to make otherwise inaccessible aromatic dicarboxylic acids. The two methods were recently reviewed.
7
Appendix
Compounds Referenced (Chemical Abstracts Registry Number)
Bromothymol blue
potassium α- or β-naphthoate
phthalic or isophthalic acid
ethanol (64-17-5)
hydrochloric acid (7647-01-0)
methanol (67-56-1)
nitric acid (7697-37-2)
oxygen (7782-44-7)
potassium cyanide (151-50-8)
Benzoic acid (65-85-0)
carbon dioxide (124-38-9)
carbon (7782-42-5)
potassium hydroxide (1310-58-3)
Naphthalene (91-20-3)
2-Furoic acid (88-14-2)
cadmium chloride (10108-64-2)
Terephthalic acid (100-21-0)
2,6-Naphthalenedicarboxylic acid (1141-38-4)
1,8-naphthalic anhydride (81-84-5)
dipotassium naphthalate
dipotassium 2,6-naphthalenedisulfonate
2-methyl-6-acetylnaphthalene
dipotassium 2,6-naphthalenedicarboxylate
3,4-pyrroledicarboxylic acid
2,5-pyrroledicarboxylic acid
2,3-pyridinedicarboxylic acid (89-00-9)
2,5-pyridinedicarboxylic acid (100-26-5)
2,5-furandicarboxylic acid (3238-40-2)
2-thiophenecarboxylic acid (527-72-0)
2,5-thiophenedicarboxylic acid (4282-31-9)
2-quinolinecarboxylic acid (93-10-7)
2,4-quinolinedicarboxylic acid
2,2'-biphenyldicarboxylic acid (482-05-3)
4,4'-biphenyldicarboxylic acid
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