Sodium Chloride → 1-Hydroxynaphthalene-4,6-disulphonic acid

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반응 단계

6.8 parts of 2,4,6-trifluoro-1,3,5-triazine are added dropwise to a solution of 13.4 parts of 1,4-diaminobenzene-2,5-disulphonic acid in 200 parts by volume of water at 0° C. and a pH value of 4 to 5 is maintained by constantly neutralising the hydrogen fluoride liberated. The course of the reaction is followed chromatographically. The resulting solution of the intermediate product is condensed, at a pH value of 7 to 8 and at 10° to 20° C. with 31 parts of the aminoazo dyestuff obtained by coupling diazotised 1-aminobenzene-2-sulphonic acid with 1-(4'-nitrophenylamino)-8-hydroxynaphthalene-3,6-disulphonic acid and subsequently reducing the nitro group with sodium sulphide. The dyestuff is salted out completely with sodium chloride, filtered off, washed and again converted to a neutral solution in 500 parts by volume of water. Further diazotisation of the resulting aminoazo dyestuff and coupling with 15 parts of 1-hydroxynaphthalene-4,6-disulphonic acid gives the dyestuff of the formula ##STR43## which is precipitated with sodium chloride, isolated and then washed and dried. It is a dark red powder which gives a red solution in water.

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