Hydrogen Bromide → 5-bromonaphthalene-2-sulfonic Acid

Beteiligte Stoffe

Reaktionsschritte

5-Amino-2-naphthalenesulfonic acid (11.15 g, 50 mmol) was dissolved in 100 ml of 0.5 N NaOH solution with stirring. The dark-red solution was cooled down to 0° C. by addition of ice (~100 g). Before the ice completely dissolved, 20 ml of 40% HBr aqueous solution was added dropwise and the resulting suspension was maintained at -5° to 0° C., then 10 ml of NaNO2 (3.65 g) aqueous solution was added in 30 minutes. The mixture was stirred continuously for 30 minutes at -5~0° C. The unreacted NaNO2 was decomposed by addition of 350 mg of urea at the end of reaction. The resulting dark diazonium suspension was kept below 0° C., and added dropwise over one hour period to CuBr (7.15 g) solution in 40 ml of 40% HBr at 70° C. with vigorous stirring (the CuBr solution was in a 1000 ml flask). The dark mixture was stirred at 80° C. for 40 minutes, then cooled down to room temperature and treated with 200 ml of water. The precipitate was collected in a Buchner funnel and washed with about 50 ml of water. 13.9 g of crude product was obtained after drying under vacuum. The crude compound was refluxed in 500 ml of water for 2 hours, cooled to room temperature and filtered. The filtrate was evaporated to dryness and solid dried in vacuo to yield 8.23 g (57% yield) of pure product.

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