Hydrochloric Acid → Sulfanilic acid

Participants

Reaction Steps

25.3 parts of 3-acetylamino-1-aminobenzene-6-sulphonic acid are diazotised in 500 parts of water with hydrochloric acid and sodium nitrite. The resultant strongly acid diazo comppound is treated with 32 parts of 1-amino-8-hydroxy-naphthalene-3,6-disulphonic acid in the form of the monosodium salt and the mixture is stirred at room temperature until no more diazo compound can be detected. The coupling mixture is then neutralised with sodium hydroxide solution, treated first with 20 parts of sodium bicarbonate and then with the diazo compound obtained from 17.3 parts of sulphanilic acid. After termination of the coupling, sufficient sodium hydroxide is added to give a 6 % solution and this is heated for 2 hours to 90°C in order to split off the acetyl group. After acidification with hydrochloric acid, the aminazo dye is precipitated with sodium chloride, filtered off and again dissolved neutral in 1000 parts of water with the addition of sodium carbonate. A solution of 18.5 parts of cyanuric chloride in 80 parts of acetone is added and the mixture is stirred for 2 hours between 0° and 10°C, the pH being kept between 5 and 6 by the dropwise addition of a dilute sodium hydroxide solution. Then an aqueous solution of 5.4 parts of 1,3-diaminobenzene is added and the reaction mixture is stirred for 2 hours between 30° and 40°C, the pH being kept between 6 and 7. After termination of the condensation, the resultant dye is salted out, filtered off and dried. It dyes cellulose fibres in strong, greenish blue shades. The dye has the formula ##SPC10##

Provenance & Evidence