Org. Synth. 1946, 26, 95
DOI: 10.15227/orgsyn.026.0095
TEREPHTHALIC ACID
Submitted by C. F. Koelsch
Checked by C. F. H. Allen and J. VanAllan.
1. Procedure
One hundred grams (0.75 mole) of p-methylacetophenone1 is added to a mixture of
250 ml. (4 moles) of concentrated nitric acid (sp. gr. 1.42) and 1 l. of water in a 3-l. flask, and the mixture is refluxed in a
hood for 4 hours. After the mixture has been cooled, the sticky, yellow solid is collected on a
14-cm. Büchner funnel, pressed down well, and washed with 300 ml. of cold water.
The moist solid is mixed with 1 l. of water and 35 g. of sodium hydroxide in a 3-l. three-necked flask, fitted with a mechanical stirrer and a reflux condenser, and the stirred mixture is heated almost to its boiling point. Through the momentarily opened third neck of the flask is added, in portions of about 20 g., 300 g. (1.9 moles) of potassium permanganate, at such a rate that the boiling of the stirred mixture is maintained without external heating. After the addition has been completed, the mixture is refluxed for 2 hours; if any permanganate remains it is destroyed by the addition of 25 ml. of ethanol. The mixture is then filtered through a 14-cm. Büchner funnel, and the manganese dioxide is washed by removing it from the funnel, slurrying with 500 ml. of hot water (Note 1), and filtering.
The combined filtrates are heated nearly to boiling and acidified with a solution of 108 ml. of concentrated sulfuric acid (sp. gr. 1.84) in 400 ml. of water. After the mixture has been cooled to room temperature, the terephthalic acid is filtered and washed by stirring on the filter with three successive 100-ml. portions of cold water. The product is dried in an evaporating dish on a steam bath. The yield of terephthalic acid which sublimes at 300° or higher without melting is 105–109 g. (84–88%) (Note 2) and (Note 3).
2. Notes
1.
This extraction yields 1–2 g. of the product.
2.
The acid is analytically pure. There is no satisfactory solvent for the recrystallization of large amounts of
terephthalic acid. Small quantities may be recrystallized from
acetic acid, but the purity of a properly precipitated and washed sample is not thereby improved.
3.
The high yields of ethyl ester obtainable from the product attest its purity. A mixture of
50 g. of terephthalic acid,
500 ml. of absolute ethanol, and
25 ml. of sulfuric acid was boiled for 16 hours and then distilled to half its volume and poured into dilute aqueous
sodium carbonate. There was obtained
56.7 g. of
diethyl terephthalate (m.p.
42–44°), and from the wash water there was recovered
4.6 g. of terephthalic acid; these materials account for 93.3% of the original substance.
3. Discussion
Terephthalic acid has been obtained from a great many
p-disubstituted derivatives of
benzene or
cyclohexane by oxidation with permanganate,
chromic acid, or
nitric acid. The following routes appear to have preparative value: from
p-toluic acid,
2 p-methylacetophenone,
3 or
dihydro-p-tolualdehyde4 by oxidation with permanganate; from
p-cymene by oxidation with
sodium dichromate and
sulfuric acid;
5 from
p-dibromobenzene or from
p-chloro- or p-bromobenzoic acid by heating at 250° with
potassium and cuprous cyanides;
6 and from
p-dibromobenzene7 or
p-iodobenzoic acid,
8 butyllithium, and
carbon dioxide. It has been obtained also by the air oxidation of
p-xylene in the presence of cobalt naphthenates.
9 Oxidations of
p-toluic acid,
10 p-tolualdehyde,
11 and
α-chloro-p-xylene12 have been patented.
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
p-chloro- or p-bromobenzoic acid
potassium and cuprous cyanides
ethanol (64-17-5)
sulfuric acid (7664-93-9)
acetic acid (64-19-7)
Benzene (71-43-2)
sodium hydroxide (1310-73-2)
nitric acid (7697-37-2)
potassium permanganate (7722-64-7)
sodium carbonate (497-19-8)
carbon dioxide (124-38-9)
cyclohexane (110-82-7)
chromic acid (7738-94-5)
sodium dichromate (7789-12-0)
manganese dioxide (1313-13-9)
p-xylene (106-42-3)
p-cymene (99-87-6)
butyllithium (109-72-8)
Terephthalic acid (100-21-0)
diethyl terephthalate (636-09-9)
p-Toluic acid (99-94-5)
p-dibromobenzene (106-37-6)
p-Methylacetophenone (122-00-9)
p-iodobenzoic acid (619-58-9)
p-Tolualdehyde (104-87-0)
dihydro-p-tolualdehyde
α-chloro-p-xylene (104-82-5)
Copyright © 1921-, Organic Syntheses, Inc. All Rights Reserved