Synthesis of 4-aminosalicylic acid

Preparation of 4-aminosalicylic acid

Preparation of 4-aminosalicylic acid

Preparation of 4-aminosalicylic acid

11 g of very thick paste of 5-(phenylazo)salicylic acid sodium salt is treated with 80 ml. 40% of sodium hydroxide solution, and the mixture is heated to 80°C. to form a clear solution. In the course of 15 minutes 80 grams of powdered sodium dithionite, is added to this solution with stirring at a temperature of 80-90°. The solution becomes lighter in color and is completely decolorized within a few minutes after the addition of the sodium dithionite is completed. Persistence of color after 15 minutes indicates that the sodium dithionite used was not good, and more of it must be added until the solution is colorless. (Water-free sodium dithionite is quite stable in the presence of oxygen as long as it remains completely dry; if moisture is present, the material decomposes rapidly, generating sulfur dioxide and clumping together. Good hydrosulfite should be a free-flowing, odorless powder.) If necessary, additional sodium hydroxide is added to keep the solution strongly alkaline to phenolphthalein at all times. When the reaction is completed, as shown by decolorization, the aniline which is formed is distilled out with steam, heating the distillation flask enough so that constant volume (about 500 ml.) is maintained. When all of the aniline has been removed, the residual solution is filtered through a fluted filter paper and concentrated hydrochloric acid is added slowly and with good stirring to the hot filtrate until it shows a faint acid reaction to litmus. This requires about 80 ml. concentrated hydrochloric acid for the quantities of materials used here. The 4-aminosalicylic acid separates as a distinctly crystalline, gray-white precipitate. An excess of hydrochloric acid must be avoided or the product will redissolve by forming 4-aminosalicylic acid hydrochloride. An alternate procedure is to neutralize most of the alkali with hydrochloric acid, and the last part with acetic acid. After standing overnight, the 4-aminosalicylic acid is removed by suction filtration, washed with cold water, and dried at about 80°. The yield is 26 to 28 grams, or 85 to 90 % of the theoretical amount. The material dissolves to form clear solutions in dilute hydrochloric acid and in alkali.

The fundamental processes of dye chemistry, by H. E. Fierz-David, 157-158, 1949


4-amino-2-hydroxybenzoic acid



InChI Key


Canonical SMILES


MeSH Synonyms

4 Aminosalicylic Acid, 4-Aminosalicylic Acid, Acid, Aminosalicylic, Alumino 4 Aminosalicylic Acid, Alumino-4-Aminosalicylic Acid, Aminosalicylic Acid, p Aminosalicylic Acid, p Aminosalicylic Acid Monolithium Salt, p Aminosalicylic Acid Monopotassium Salt, p Aminosalicylic Acid Monosodium Salt, p-Aminosalicylic Acid, p-Aminosalicylic Acid Monolithium Salt, p-Aminosalicylic Acid Monopotassium Salt, p-Aminosalicylic Acid Monosodium Salt, p-Aminosalicylic Acid, Aluminum (2:1) Salt, p-Aminosalicylic Acid, Calcium (2:1) Salt, p-Aminosalicylic Acid, Monosodium Salt, Dihydrate, Pamisyl, para Aminosalicylic Acid, para-Aminosalicylic Acid, Rezipas

Depositor-Supplied Synonyms

4-Aminosalicylic acid, 4-Amino-2-hydroxybenzoic acid, 65-49-6, Aminosalicylic acid, P-AMINOSALICYLIC ACID, Pamisyl, Rezipas, Aminopar, Deapasil, Ferrosan, Parasalindon, Aminox, Paser, Parasalicil, Entepas, Gabbropas, Pamacyl, Paramycin, Parasal, Pasalon, Pasdium, Pasnodia, Pasolac, Propasa, Apacil, Osacyl, Pasara, Pasem, Pasmed, Pasa, Para-Pas, Sanipirol-4, 2-Hydroxy-4-aminobenzoic acid, Para-aminosalicylic acid, Hellipidyl, Pascorbic, para-Amino salicylic acid, APAS, PASK, PAS-C, Benzoic acid, 4-amino-2-hydroxy-, PAS (acid), PAS, Sanipriol-4, Kyselina p-aminosalicylova, Salicylic acid, 4-amino-, 3-Hydroxy-4-carboxyaniline, Aminosalyl, Neopasalate, Helipidyl, Paser Granules, Amino-pas, 4-Aminosalicylate, NIH 2939, NSC 2083, 4-amino-2-hydroxy-benzoic acid, 4-Asa, A 1909, PAS (VAN), Aminosalicylic Acid [USP], UNII-5B2658E0N2, CHEBI:27565, HSDB 3203, NSC2083, WUBBRNOQWQTFEX-UHFFFAOYSA-N, Kyselina p-aminosalicylova [Czech], EINECS 200-613-5, MFCD00007789, BRN 0473071, 4-amino-salicylic acid, AI3-50142, Aminosalicylic acid (USP), PASKALIUM, TEEBACIN, AMINOSALICYLATE SODIUM, MLS000069579, SMR000059110, SMR000058830, Aminosalicylic, Rexipas, Alumino-4-Aminosalicylic Acid, ISONICOTINIC ACID HYDRAZIDE P-AMINOSALICYLATE SALT, Pamisyl (TN), 4-Aminosalicylicacid, p-amino salicylic acid, 4-amino salicylic acid, PubChem23542, Spectrum_000042, .gamma.-Aminosalicylate, ACMC-1BIVG, Spectrum2_000001, Spectrum3_000297, Spectrum4_000145, Spectrum5_000804, WLN: ZR CQ DVQ, AC1L1IN4, AC1Q51QM, Nemasol Sodium Tab 500mg, Salicyclic acid, 4-amino-, SCHEMBL2262, CHEMBL1169, P.A.S, A79604_ALDRICH, BSPBio_001834, KBioGR_000590, KBioSS_000422, ZINC922, KSC489M8R, MLS000069418, MLS001148121, BIDD:GT0175, DivK1c_000350, SPBio_000001, p-Aminosalicylic acid STANDARD, BDBM48319, CTK3I9688, HMS501B12, KBio1_000350, KBio2_000422, KBio2_002990, KBio2_005558, KBio3_001334, 4-azanyl-2-oxidanyl-benzoic acid, cid_11988145, NINDS_000350, BB_SC-7182, HMS2090I07, HMS2093L14, HMS2236I04, HMS3371A17, KUC106682N, NSC-2083, 133-09-5 (mono-potassium salt), ANW-35052, BBL013175, CCG-39969, SBB056794, STL163955, AKOS000121200, 133-10-8 (mono-hydrochloride salt), 5B2658E0N2, CS22593, DB00233, MCULE-4841633599, RP21704, RTR-022285, TRA0077674, 4-AMINO,2-HYDROXY-BENZOIC ACID, AMINOSALICYLIC ACID RESIN COMPLEX, IDI1_000350, NCGC00018110-01, NCGC00018110-02, NCGC00018110-03, NCGC00018110-04, 133-15-3 (calcium (2:1) salt), AC-12894, AJ-07939, AK-46320, BC205364, BR-46320, KB-79579, OR025131, OR175020, OR276464, SC-18342, KSC-11-207-13, DB-054818, KB-173065, KB-189056, LS-144220, ST2411073, TR-022285, A0420, FT-0689453, H2354, ST50824394, C02518, D00162, M-5913, 11059-EP2269610A2, 11059-EP2269988A2, 11059-EP2270008A1, 11059-EP2275413A1, 11059-EP2277848A1, 11059-EP2287156A1, 11059-EP2289510A1, 11059-EP2292617A1, 11059-EP2295053A1, 11059-EP2301940A1, 11059-EP2316457A1, 11059-EP2316458A1, 11059-EP2316825A1, 11059-EP2316826A1, 11059-EP2316827A1, 11059-EP2316828A1, 11059-EP2371811A2, 50409-EP2272825A2, 50409-EP2298776A1, 50409-EP2301544A1, 50409-EP2311809A1, AB00051913-20, 122903-EP2270002A1, 122903-EP2295053A1, 4-14-00-01967 (Beilstein Handbook Reference), 6018-19-5 (mono-hydrochloride salt, di-hydrate), I04-1463, Q-200437, T5373193, 3B3-030325, InChI=1/C7H7NO3/c8-4-1-2-5(7(10)11)6(9)3-4/h1-3,9H,8H2,(H,10,11

Removed Synonyms

mesalamine, 4-aminopyridine, -aminosalicylic acid, Acid, Aminosalicylic, p Aminosalicylic Acid, 4 Aminosalicylic Acid, Sodium p-aminosalicylate, para Aminosalicylic Acid, C7H7NO3, Alumino 4 Aminosalicylic Acid, CID4649, NSC 38877, p Aminosalicylic Acid Monosodium Salt, p-Aminosalicylic Acid Monosodium Salt, p Aminosalicylic Acid Monolithium Salt, p-Aminosalicylic Acid Monolithium Salt, p Aminosalicylic Acid Monopotassium Salt, p-Aminosalicylic Acid Monopotassium Salt, p-Aminosalicylic Acid, Calcium (2:1) Salt, p-Aminosalicylic Acid, Aluminum (2:1) Salt, D010131, p-Aminosalicylic Acid, Monosodium Salt, Dihydrate, BHA, 6018-19-5, 89-57-6

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