Carbon Dioxide → 3-Hydroxy-2-naphthoic acid

Participants

Reaction Conditions

Reaction Steps

A stirred autoclave is charged with 1260 parts of β-naphthol, 592 parts of aqueous caustic soda solution (50% by weight) and 40 parts of aqueous caustic potash solution (85% by weight). The mixture is mixed well under nitrogen until it has heated up to an internal temperature of 260° C. and is kept for thirty minutes at this temperature. Dehydration is then practically complete. Carboxylation is carried out in an autoclave at a temperature of 260° C. with dry carbon dioxide at a pressure of 7 atmospheres. The absorption of carbon dioxide is monitored by a gas meter. After absorption has ended β-naphthol is distilled off at 20 mm and then in the manner described above carbon dioxide is again forced in. The β-naphthol is again distilled off and carboxylation is carried out for a third time. Within a carboxylation period of three hours a total of 300 parts of carbon dioxide is absorbed. The autoclave is then cooled and the reaction mixture is stirred with a solution of 90 parts of sodium hydroxide in 5000 parts of water at 95° to 100° C. While stirring vigorously the aqueous phase is acidified to pH about 6 with hydrochloric acid. The β-naphthol thus deposited is cooled to 30° C. and suction filtered; the clear aqueous filtrate is acidified with hydrochloric acid (35% by weight) at a temperature of from 85° to 90° C. to a pH of 3 and stirred for another ten minutes. The crystals of 2-hydroxynaphthalene-3-carboxylic acid formed are suction filtered and dried in vacuo at 70° C. 510 parts of end product (68% of theory based on the reacted β-naphthol) is obtained with a melting point of 215° to 219° C.

Provenance & Evidence