Sulfuric Acid → 3-Hydroxy-2,6-naphthalenedisulfonic acid

Participants

Reaction Conditions

Reaction Steps

7-Hydroxynaphthalene-2-sulfonic acid (250 g, 1.16 mol) was added in portions to a mixture of concentrated H2SO4 (950 g) and water (50 g). The mixture was stirred at 110-120° C. for 3 hours, cooled to room temperature, added to a mixture of ice and water (5000 ml) and the product precipitated by the addition of sodium chloride. The resultant slurry was warmed to 90° C. to dissolve the product, stirred for 1 hour at this temperature and then allowed to cool. The product was filtered off and the damp product dissolved in water (3000 ml) at pH 10 by the addition of concentrated sodium hydroxide solution. The solution was then filtered to remove a small amount of insoluble material. The pH of the filtrate was lowered to 7 with concentrated HCl and the product precipitated by the addition sodium chloride. The product was filtered off and dried in a vacuum oven to give 117 g of a cream solid (68% yield).

Provenance & Evidence