Hydrochloric Acid → 8-(3-Nitro-p-toluamido)-1,3,5-naphthalenetrisulfonic acid trisodium salt

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Reaction Steps

To a stirred solution of 22.5 g of 8-amino-1,3,5-naphthalenetrisulfonic acid trisodium salt in 160 ml of water is added 11.0 g of the preceding product with a small amount of ether. Stirring is continued, and after one hour 1.0 g of sodium acetate trihydrate and 1.0 g of 3-nitro-p-toluoyl chloride are added. The mixture is stirred an additional 3 hours and the above addition of sodium acetate and 3-nitro-p-toluoyl chloride is repeated. The mixture is stirred an additional hour, acidified to Congo Red indicator paper with hydrochloric acid and filtered. The filtrate is neutralized with sodium hydroxide, concentrated, dissolved in 50 ml of water and added to one liter of ethanol with stirring for 16 hours. The solid is filtered and forms a gel on washing with ethanol. The gel is dissolved in water and evaporated. The residue is dissolved in 35 ml of hot water and 320 ml of absolute ethanol is added with stirring. The mixture solidifies and water is added to allow filtration. The solid is washed with ether and dried in vacuo. The filtrate is treated by stirring with one liter of ethanol, the separated solid is collected, washed with ether, and dried to yield a combined total of 23.9 g of 8-(3-nitro-p-toluamido)-1,3,5-naphthalenetrisulfonic acid trisodium salt.

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