Org. Synth. 1953, 33, 94
DOI: 10.15227/orgsyn.033.0094
3-THENOIC ACID
[3-Thiophenecarboxylic acid]
Submitted by E. Campaigne and William M. LeSuer
1.
Checked by Charles C. Price and E. A. Dudley.
1. Procedure
Silver oxide is prepared by adding a solution of
150 g. (0.88 mole) of silver nitrate in 300 ml. of water to a solution of
70 g. (1.75 moles) of sodium hydroxide in 300 ml. of water. Continuous shaking during the addition ensures complete reaction and results in a brown semisolid mixture. To this mixture, contained in a
1-l. flask which is cooled in an
ice bath, is added
47.5 g. (0.425 mole) of 3-thenaldehyde (
p. 918) in small portions with stirring. The oxidation is complete in about 5 minutes after the last of the aldehyde has been added. The black
silver suspension is removed by suction filtration
(Note 1) and is washed with several portions of hot water. The cold combined filtrate and washings are acidified with concentrated
hydrochloric acid, precipitating
49 g. of
3-thenoic acid, which melts at
136–137°. Concentration of the mother liquors gives another
3–4 g. of acid, making a total of
52–53 g. (
95–97%). Recrystallization of this acid from water raises the melting point to
137–138°.
2. Notes
1.
This
silver dissolves readily in concentrated
nitric acid and may be used over and over in oxidations.
3. Discussion
3-Thenoic acid has been prepared in low yield by oxidation of
3-methylthiophene with
potassium permanganate,
2,3,4 dilute
nitric acid,
chromic acid, and
hydrogen peroxide,
4 and by reductive dechlorination of
chloro-3-thenoic acid.
4 Starting with
3-iodothiophene, which is difficult to obtain, good yields are obtained by the Grignard procedure
5 or with
cuprous cyanide and
potassium cyanide in a
sealed tube.
6 3-Thenoic acid has been made also from
3-bromothiophene by reaction with
cuprous cyanide in
quinoline, followed by hydrolysis,
7 and by carbonation of the Grignard reagent from
3-bromothiophene which is prepared by entrainment with
ethyl bromide.
8
Oxidation of the aldehyde was not used earlier because of the difficulty of obtaining the aldehyde, which is now readily available by the Sommelet synthesis from
3-thenyl bromide. Campaigne and LeSuer
9 also used alkaline permanganate as the oxidizing agent, but the yields decreased to
40–60%. The present procedure gives an over-all yield from
3-methylthiophene of about
45%.
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
hydrochloric acid (7647-01-0)
sodium hydroxide (1310-73-2)
nitric acid (7697-37-2)
potassium permanganate (7722-64-7)
silver oxide (20667-12-3)
silver nitrate (7761-88-8)
Ethyl bromide (74-96-4)
Cuprous Cyanide (544-92-3)
potassium cyanide (151-50-8)
chromic acid (7738-94-5)
hydrogen peroxide (7722-84-1)
Quinoline (91-22-5)
silver (7440-22-4)
3-Methylthiophene (616-44-4)
3-Thenaldehyde
3-Thenyl bromide
3-Thenoic acid
3-Bromothiophene (872-31-1)
3-Thiophenecarboxylic acid (88-13-1)
chloro-3-thenoic acid
3-iodothiophene (10486-61-0)
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