Acid blue 145

Preparation of Acid Blue 145 from the Condensation Reaction of Bromaminic Acid and Aromatic Amines

Yuyin Zhang, et al. Ningbo Chemical Industry, 2003 (3), 42-44.

There are two common synthesis routes for acid blue 145. One is that bromaminic acid is condensed with p-toluidine and then sulfonated. The other is the condensation of bromaminic acid and 2-amino-5-methylbenzenesulfonic acid. The condensation reaction between bromaminic acid and arylamine is a nucleophilic substitution reaction.
Steps to synthesize acid blue 145 according to route 1
· Stir bromaminic acid, 150ml water, 150ml ethanol, 20g p-toluidine and 35g acid binding agent in a water bath heating (75-80°C).
· Then slowly add 10g of mixed catalyst and control the addition to complete in 1 hour. Continue the reaction for 6 hours, raise the temperature and evaporate to recover ethanol.
· After steaming, add 200ml of water and adjust the pH to 1-2 with HCl. After holding for half an hour, filter, clean and dry the filter cake to collect the color base of acid blue 145.
· Slowly add the prepared Acid Blue 145 color base to fuming sulfuric acid (cooled to room temperature), and then raise the temperature to 40-50°C until the color base disappears. Dilute the sulfonation solution into ice-cold sodium chloride solution, filter, salt out, and dry to obtain acid blue 145 original dye.