Tartrazine → 8-[5-(4-Nitro-2-sulfobenzamido)-o-toluenesulfonamido]-1,3,6-naphthalenetrisulfonic acid

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Reaction Steps

To a stirred solution of 9.0 g of 8-(5-amino-o-toluenesulfonamido)-1,3,6-naphthalenetrisulfonic acid, trisodium salt, and 3.34 g of sodium acetate trihydrate in 47.0 ml of water chilled to 0° C. in an ice bath is added 4.29 g of 4-nitro-2-sulfobenzoic acid anhydride in one portion. The mixture is stirred for a total of 10 minutes in the ice bath and the undissolved material is separated. The solution, at 0° C., is acidified with 1.38 ml of concentrated hydrochloric acid, then is added dropwise, with vigorous stirring, to 750 ml of absolute ethanol. The product is collected, washed with 85% aqueous ethanol, ethanol and ether and is dried to yield 11.75 g of 8-[5-(4-nitro-2-sulfobenzamido)-o-toluenesulfonamido]-1,3,6-naphthalenetrisulfonic acid, tetrasodium salt.

Provenance & Evidence