Carbon Dioxide → 3-Hydroxy-2-naphthoic acid

Participants

Reaction Conditions

Reaction Steps

A stirred autoclave is charged with 1220 parts of β-naphthol, 608 parts of aqueous caustic soda solution (50% by weight) and 27 parts of aqueous caustic potash solution (85% by weight). The mixture is well mixed under nitrogen, heated to an internal temperature of 260° C and kept for 30 minutes at this temperature. The dehydration is then practically complete. Carboxylation is carried on for 3 hours at a temperature of 260° C with dry carbon dioxide at a pressure of 7 atmospheres. The absorption of CO2 is monitored by a gas meter. After the absorption is ended 350 parts of β-naphthol is distilled off at 20 mm of Hg and then in the manner above described carbon dioxide is again forced in and the mixture carboxylated for 2 hours. A total of 300 parts of carbon dioxide is absorbed in a carboxylation period of 300 minutes. The reaction mixture is stirred with 5000 parts of water and dissolved. The solution is cooled to 80° to 90° C, acidified with 50% by weight sulfuric acid to a pH of 6.5 and then extracted for fifteen minutes with a total of 800 parts of a mixture of m-xylene and p-xylene in the ratio 2.3:1. The phases are then separated and the aqueous phase is acidified to a pH of 3 at 90° C with 50% by weight sulfuric acid. The precipitated 2-hydroxynaphthalene-3-carboxylic acid is separated by filtration from the hot solution at 80° C. 530 parts of 2-hydroxynaphthalene-3-carboxylic acid is obtained. This is 73% of theory based on reacted naphtholate deducting the β-naphthol obtained. It contains 99% by weight of 2-hydroxynaphthalene-3-carboxylic acid and 0.5% by weight of β-naphthol. The melting point is 218° to 220° C.

Provenance & Evidence