Study on the Manufacture of 1-Naphthol-2-carboxylic Acid

Abstract

Application of the Kolbe-Schmidt reaction to 1-naphthol was examined in order to prepare 1-naphtholcarboxylic acids. At first the method for the analysis of 1-naphthol-2-and 4-carboxylic acids, and 1-naphthol was exploited. Gas chromatography of the mixture after trimethylsilylation was found to be effective. A Kolbe-Schmidt reaction of sodium or potassium salt of 1-naphthol gave 1-naphthol-2-carboxylic acid exclusively and no trace of 1-naphthol-4-carboxylic acid was detected. The best conditions were : reaction temperature, 120-140°C ; pressure of carbon dioxide, more than 5 kg/cm² ; reaction time, 3-6 hr. The yield of 1-naphthol-2-carboxylic acid was more than 90% and the recovery of the starting material was only 5-7%, accompanied with ca. 1% of an unidentified product (probably polycarboxylic acid).