Tartrazine → 8-[3-(4-Nitro-2-sulfobenzamido)-p-toluamido]-1,3,5-naphthalenetrisulfonic acid

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Reaction Steps

To a stirred solution of 6.5 g of 8(3-amino-p-toluamido)-1,3,5-naphthalenetrisulfonic acid, trisodium salt (prepared in Example 1) and 2.4 g of sodium acetate trihydrate in 43.0 ml of water is added 3.07 g of 4-nitro-2-sulfobenzoic acid anhydride. The mixture is stirred for 30 minutes then is filtered. The filtrate is acidified with 0.98 ml of concentrated hydrochloric acid and evaporated in vacuo. The residue is dissolved in 20 ml of hot water which is added to 130 ml of absolute ethanol forming a gelatinous precipitate. The material is collected and washed with 80% aqueous ethanol, ethanol and ether and is dried to yield 4.2 g of 8-[3-(4-nitro-2-sulfobenzamido)-p-toluamido]-1,3,5-naphthalenetrisulfonic acid, tetrasodium salt.

Provenance & Evidence