Chemical Properties
yellow to beige-brown fine crystalline powder. 3 -Hydroxy-2-naphthoic acid [92-70-6], BON acid, C11H8O3, Mr 188.17, mp 222℃, forms pale yellow crystals from aqueous ethanol. Alkaline solutions have a green fluorescence. Aqueous ferric chloride produces a blue color, and warming with CHCl3– NaOH results in a green color. Oxidation with alkaline permanganate gives 2-carboxyphenylglyoxylic acid and then phthalic acid. Dry distillation produces dibenzoxanthone. Bromination gives the 4,7-dibromo derivative; nitration, the 4-nitro derivative; and sulfonation with oleum, the 5,7-disulfonic acid derivative.
Uses
2-hydroxy-3-naphthoic acid (BON) is coupled with diazo compounds
and their calcium salts are bright red bleed resistance pigments. The somewhat higher cost manganese salt shows better exterior
durability than the calcium or barium salts. The BON red pigments are
characterized by an extremely high degree of color stability, resistance
to acids and alkalies and are nontoxic.
Uses
3-Hydroxy-2-naphthoic acid is mainly used as intermediate for the production of dyes and pigments. Further uses are as intermediate for insecticides and pharmaceuticals (ECB, 2000).
Preparation
3 -Hydroxy-2-naphthoic acid is invariably by the Kolbe – Schmitt reaction of carbon dioxide with the dried sodium salt of 2-naphthol at 220 – 260℃. Many improvements in both process and equipment have been developed. The main problems are removal of the 50 % unreacted 2-naphthol and avoidance of a tarry byproduct. Yields of 80 % based on the amount of 2-naphthol consumed are possible despite the low conversion.
Definition
ChEBI: 3-Hydroxy-2-naphthoate is a naphthoic acid.
Purification Methods
Crystallise it from water or acetic acid. The S-benzyisothiuronium salt has m 216-217o (from EtOH). It forms many metal complex salts. [Beilstein 10 H 333, 10 III 1084.]
