Org. Synth. 1953, 33, 94
DOI: 10.15227/orgsyn.033.0094
[3-Thiophenecarboxylic acid]
Submitted by E. Campaigne and William M. LeSuer1.
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 procedure5 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 LeSuer9 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%.

References and Notes
  1. Indiana University, Bloomington, Indiana.
  2. Muhlert, Ber., 18, 3003 (1885).
  3. Damsky, Ber., 19, 3282 (1886).
  4. Voerman, Rec. trav. chim., 26, 293 (1907).
  5. Steinkopf and Schmitt, Ann., 533, 264 (1938).
  6. Rinkes, Rec. trav. chim., 55, 991 (1936).
  7. Nishimura, Motoyama, and Imoto, Bull. Univ. Osaka Prefect., Ser. A, 6, 127 (1958) [C. A., 53, 4248 (1959)].
  8. Gronowitz, Arkiv Kemi, 7, 267 (1954).
  9. Campaigne and LeSuer, J. Am. Chem. Soc., 70, 1555 (1948).

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-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)