Phosphoric Acid → Quinacridone

Participants

Reaction Conditions

Reaction Steps

One hundred and thirty-five ml of polyphosphoric acid and 65 ml of 85% phosphoric acid are mixed in a mechanically stirred beaker and cooled to 50° C. Four grams of 2,5-di(phenylamino)terephthalic acid (DAA) are slowly added in small portions and under agitation by Gifford-Wood homogenizer. Each portion is dissolved before adding another one, checked by dipping a glass rod into the viscous reaction mixture and examining for solid particles clinging to the rod. During this time, the temperature of the reaction mixture is kept at 55° C. or below by cooling with an external water bath. After having dissolved all of the DAA, the solution is heated to 100° C. under stirring and kept at that temperature for 1 hour. The reaction mixture is cooled and poured into 2 l of water under mechanical stirring. The slurry which forms is stirred for 10 minutes and filtered. The filter cake is washed acid-free with water and the water-wet solid reslurried in 600 ml of water. The pH of the slurry is adjusted to 12 with concentrated 50% by weight aqueous NaOH solution under stirring. The slurry is heated to 60° C., held at that temperature for 10 minutes with continued stirring and filtered immediately. The filter cake is washed with water and dried in a vacuum oven at 70°-80° C. to give 0.55 g (15% yield) of quinacridone by-product. Combined filtrate and wash water are stirred and acidified with acetic acid to a pH of 4. The formed precipitate is stirred for 10 minutes, filtered and washed acid-free with water. Vacuum oven drying overnight at 70°-80° C., under slight N2 purge, gives 2.8 g (74% yield) of orange microcrystalline 2-(phenyl)amino-3-carboxy-9(10H) acridinone.

Provenance & Evidence