2-Hydroxy-1-naphthoic acid

2-Hydroxy-1-naphthoic acid [2283-08-1], C11H8O3, Mr 188.17, has a mp of 156 – 157℃ (decomp. to 2-naphthol and CO2). The monosodium salt is unstable in hot aqueous solution. 2- Hydroxy-1-naphthoic acid is decarboxylated by nitrous acid, forming 1-nitroso-2-naphthol, and by diazo salts, forming a 1-azo-2-naphthol. An ethanolic solution of 2-hydroxy-1-naphthoic acid gives a dark blue color with iron(III) chloride. Chlorosulfonic acid at 30℃ gives the 6-sulfonyl chloride derivative.

2-Hydroxy-1-naphthoic acid is an intermediate of minor importance in the synthesis of azo dyes.

Treatment of the dried sodium or potassium salt of 2-naphthol with carbon dioxide at 120 C under pressure gives an 80 % yield of product after careful work-up. Solvents such as toluene, tetralin, or diphenyl oxide are patented alternatives.