Preparation of 5-(phenylazo)salicylic acid
A solution is made of 18.6 grams (0.2 mole) of aniline in a mixture of 45 ml. concentrated hydrochloric acid and 45 ml. water. The solution is cooled to 0°C. in an ice-salt bath, and a solution of 14 grams of sodium nitrite in 40 ml. water is added slowly with good stirring so that the temperature does not rise above 2°. Stirring is continued for 10 minutes, after which the solution should be strongly acid to Congo red and give a weak test for nitrite with starch-iodide paper. (If the weak nitrite reaction is not obtained, a few more drops of nitrite solution should be added) 4 grams of sodium carbonate is now added carefully to neutralize most of the excess hydrochloric acid, leaving the solution very slightly acid to Congo red. The solution is then added slowly to a stirred, cold solution of 28 grams of salicylic acid (0.2 mole) in a mixture of 33 ml. sodium hydroxide solution, 67 ml. water, and 2 grams of sodium carbonate. The temperature is kept below 5° by external cooling. The coupling reaction begins immediately with the formation of a deep yellow color, and at the start, the diazonium compound disappears instantaneously. When about half of the diazo solution has been added, 5-(phenylazo)salicylic acid begins to separate and soon a thick, brownish paste is formed. The coupling reaction is now slower, and after all of the diazo solution has been added, stirring must be continued for 5 to 6 hours at 0-5°, until no diazo compound is detectable in the reaction mixture. 5-(Phenylazo)salicylic acid sodium salt is almost completely precipitated in finely crystalline form and can easily be obtained in a pure state, if desired, by filtering and washing with dilute salt solution. 5-(Phenylazo)salicylic acid sodium salt is converted to 5-(phenylazo)salicylic acid by neutralizing with hydrochloric acid.
The fundamental processes of dye chemistry, by H. E. Fierz-David, 153-154, 1949
2-Hydroxy-5-(2-phenyldiazenyl)benzoic Acid, 3147-53-3, 5-(Phenylazo)salicylic acid, 2-Hydroxy-5-(phenyldiazenyl)benzoic acid, Phenylazosalicylic Acid, AC1NV8YI, SCHEMBL137145, CK 46A, MolPort-008-434-363, EINECS 221-569-3, 3396AB, STL139171, 2-Hydroxy-5-(phenylazo)benzoic Acid, AKOS005134022, ZINC100004117, MCULE-8484078877, NSC 163392, OR058067, DB-020689, TC-162033, 4CH-019134, FT-0673722, 2-hydroxy-5-[(E)-phenyldiazenyl]benzoic acid, (3Z)-6-oxo-3-(phenylhydrazinylidene)cyclohexa-1,4-diene-1-carboxylic acid, (3E)-6-OXO-3-(2-PHENYLHYDRAZIN-1-YLIDENE)CYCLOHEXA-1,4-DIENE-1-CARBOXYLIC ACID
C13H10N2O3, CID5473969, C.I. Mordant Yellow 18, monosodium salt
3147-53-3, 2-Hydroxy-5-(phenyldiazenyl)benzoic acid, 5-(Phenylazo)salicylic acid, 2-hydroxy-5-phenyldiazenyl benzoic acid, (E)-2-hydroxy-5-(phenyldiazenyl)benzoic acid, AC1NTL4F, CTK4G7218, 5-[(E)-Phenylazo]salicylic acid, MolPort-001-834-002, ANW-73288, CP-025, ZINC16982974, 2-hydroxy-5-phenyldiazenylbenzoic acid, AKOS024333040, ZINC100061734, AJ-69846, KB-24483, OR182136, Benzoic acid,2-hydroxy-5-(2-phenyldiazenyl)-, 6-oxo-3-(phenylhydrazinylidene)cyclohexa-1,4-diene-1-carboxylic acid
CID5383300, C.I. Mordant Yellow 18, monosodium salt