2-Naphthol → 3-Hydroxy-2-naphthoic acid

Participants

Reaction Conditions

Reaction Steps

A stirred autoclave is charged with 1220 parts of β-naphthol, 620 parts of caustic soda solution of 50% by weight strength and 360 parts of 1,4-diphenoxybutane. As described in Example 4 the autoclave is heated to an internal temperature of 260° C. while stirring and kept at this temperature for ten minutes. Residual moisture is removed from the autoclave for five minutes at a pressure of 40 mm. Dehydration is practically complete. Carbon dioxide is then passed into the autoclave at the internal temperature of 260° C. up to a pressure of 7 atmospheres. Carboxylation followed by processing are carried out analogously to Example 4. The mixture of organic phase and aqueous phase is acidified to pH about 5 at a temperature of 95° C. with vigorous stirring so that the β-naphthol liberated is taken up by the solvent. The organic phase is separated from the aqueous layer. The clear aqueous phase is heated to 85° to 90° C., acidified with hydrochloric acid to pH about 3 and stirred for another 10 minutes. After cooling to 50° C. the yellowish crystals of 2-hydroxynaphthalene-3-carboxylic acid are suction filtered and dried in vacuo at 70° C. 560 parts of 2-hydroxynaphthalene-3-carboxylic acid (77% of theory based on β-naphthol reacted) is obtained with a melting point of 214° to 217° C.

Provenance & Evidence